The Cockroach FAQ.

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  1. Why do males have shorter wings?
  2. How do you sex cockroaches?
  3. Desperately seeking Blaberus giganteus?
  4. Do cockroaches sleep?
  5. Are cockroaches resistant to radiation?
  6. Why do cockroaches die on their backs?
  7. Do cockroaches bite?
  8. Is there a non-toxic way to kill cockroaches?
  9. American cockroach lifespan?
  10. Blaberus discoidalis lifespan?
  11. Lobsters called "roaches of the sea"?
  12. Are cockroaches really clean?
  13. Can cockroaches live without their head?
  14. Do cockroaches make sounds?
  15. Green cockroach?
  16. 20 lb cockroach?
  17. Live cockroach in beer bottle?
  18. Do cockroaches fly?
  19. Do cockroaches respond to light?
  20. Could cockroach eggs hatch from an infected tongue?
  21. How do cockroaches breathe?
  22. Is the cockroach's brain spread around its body?
  23. What are cockroaches good for?
  24. Albino cockroaches?
  25. Do cockroaches hibernate?
  26. Why GERMAN cockroach?
  27. Cockroach survival in cold climates?
  28. What do cockroaches eat?
  29. Do cockroach eggs survive being stepped on?
  30. Are cockroaches members of the Carp (fish) Family?
  31. Color of cockroach blood?
  32. Do cockroaches like air conditioning?
  33. Are single cockroach sightings scouts?
  34. How big is a cockroach baby?
  35. Trouble maintaining cockroaches sent to Albany?
  36. Do cockroaches have a support system?
  37. Is the cockroach exoskeleton an improvement over the worm?
  38. Could cockroaches develop albino mutants in the wild? Are they rare?
  39. How do Cockroaches Digest and what organs do they use to do so?
  40. Do cockroaches glow under black light? Are they flourescent?
  41. Can cockroaches predict earthquakes?
  42. What would cockroach vision be like?
  1. How can I tell if a cockroach is breathing?
  2. What is the reason for cockroach swarming?
  3. Do male and female cockroaches of the same size have the same blood volume?
  4. Where did the cockroach get its name?
  5. What is the cockroach reproductive cycle?
  6. Roach control safe and non-toxic for an invalid and companion dog.
  7. Do cockroaches have emotions?
  8. Cockroach ranches producing methane?
  9. Can the headless cockroach mate and give birth?
  10. Is a headless cockroach still alive if it does not move?
  11. Do cockroaches have any symbiotic relationships?
  12. Australian cockroaches in the USA?
  13. Are cockroaches social?
  14. How fast are cockroaches?
  15. Why do cockroaches cause childhood asthma?
  16. How many offspring can a cockroach have?
  17. Any info on Blaberus colloseus?
  18. How much weight can a cockroach carry?
  19. Little brown sac?
  20. Anal protrusions pointed during fighting?
  21. Cockroach surviving microwave?
  22. Can roaches move with you!?
  23. How do you sex larval cockroaches?
  24. Do cockroach injuries heal?
  25. Cockroach as big as a cat or dog?
  26. Color cockroaches most attracted to?
  27. Why no photos of cockroach eggs on the web?
  28. Can cockroaches lay eggs without mating?
  29. Do Cockroaches like to be touched?
  30. Where do cockroaches put their egg cases?
  31. How do cockroaches walk on walls?
  32. Why are cockroaches attracted to me?
  33. How did cockroaches get into our product?
  34. (Pest) cockroaches making sounds?
  35. What other insects or arachnids are related to the cockroach?
  36. Could golf course runoff generate a shoebox sized cockroach?
  37. Can female-only set of hissing cockroaches give birth 7 monthas after purchase?
  38. Cockroach brain as possible antibiotic against MRSA and E. coli? C
  39. Roach on the refrigerator shelf escapes ...
  40. Can Cockroaches sense fear ... from human bodies?
  41. Where do cockroach's bodies go after their lifespan?
  42. Do cockroaches fly more at higher temperatures?
  43. German cockroach winter survivability and freeze tolerance?

Q85: Peter asks:
Hey Joe,
Thanks for putting together The Cockroach FAQ website.

I have hit a wall in my search for information on the German cockroach winter survivability and freeze tolerance. I hope I can pick your brain on the topic.

My partner discovered German cockroaches in her apartment. The exterminators could not provide pet safety assurances about the pesticides they intended to use for the treatment. Instead, to keep the pets safe, she decided to move out of the apartment and keep her stuff in a storage pod during the cold winter.

I am tasked to determine if the German cockroaches (and their eggs, egg cases, larvae, and nymphs) stand a chance against the several weeks of -20°C to -40°C (-4°F to -40°F) weather up here in Edmonton, Alberta, Canada.

So far, I have come across this information:

Studies have shown that German cockroaches were unable to colonize inactive ships during cool temperatures and could not survive in homes without central heating in northern climates.

Without food or water, adults may die in two weeks, but they can live a month with water.

"This species is not tolerant of cold conditions."

"The major limiting factor for survival of B. germanica appears to be cold temperatures. They are unable to colonise inactive ships during cool temperatures and survival in northern climates is dependent on the presence of central heating installations (Valles, 1996). In contrast to this, Vater (1979) studied B. germanica found in a refrigerator in Germany where the temperature ranged from 7-12°C. The first to sixth larval instars were found to be mobile in this environment."

"Females carry the ootheca for up to a month, dropping it just before the eggs hatch."

"The major limiting factor for survival of B. germanica appears to be cold temperatures. They are unable to colonise inactive ships during cool temperatures and survival in northern climates is dependent on the presence of central heating installations (Valles, 1996). In contrast to this, Vater (1979) studied B. germanica found in a refrigerator in Germany where the temperature ranged from 7-12°C. The first to sixth larval instars were found to be mobile in this environment."

"Females carry the ootheca for up to a month, dropping it just before the eggs hatch."

"German cockroaches die within 10 hours when exposed to a temperature below 45°F (7.2°C). They will die within an hour if exposed to a temperature below 14°F (-10°C) as well."

"At the chilly temperature of 23°F (-5°C), 50% of German cockroaches die within 10 hours. At 14°F (-10°C), 50% die within the first hour."

Based on the above information, my reasoning leads me to believe that German cockroaches (including the adults, eggs, egg cases, larvae, and nymphs) would not survive two weeks of sustained -20°C (-4°F) conditions.

Is my conclusion reasonable or am I missing something?

Thanks in advance for your time and response,

Ans: Peter,
Good online research!

The German cockroach goes through a cold shock effect from which they will not survive. I store them for months unfed at 16°C with water. Without water they would have died of dehydration. Storing in a refrigerator at 10°C will cause the cold shock. My interest has been in keeping them healthy. My base culture and gene pool was derived from New York City and I suspect that the gene pool in Edmonton might have been selected for survival at lower temperatures and therefore anything I say is based on my New York NY origins of my lab culture. Your interest in killing has its theoretical interest to me given the tropical origin in SE Asia and ancient (Marco Polo) transport and domestication of Blattella germanica along the trade routs until it was named 'germanica' by Linnaeus. Over the years living with man I expect the gene pool changed from its tropical origins. It would be interesting to study the cold hardiness of the species along the trade routs and dispersal to cold countries worldwide.

Your idea that they should be killed by 'extreme' cold is based on firm experience in the lab. However, you should not underestimate the ability of roaches to hide in insulated areas that may benefit from heat from natural sources such as growing microorganisms such as yeast and molds. Fermentation produces heat. Also, if there are local populations of mice, the mice will create a nest of livable temperature. That is my reservation in thinking that the low outdoor temperatures of Edmonton reaching into all the hiding spaces that a roach might be using.

Good luck and tell me what you did!

Q84: Several sources ask:
With rising temperatures are we seeing cockroaches flying more?

Ans: All,
The increased gliding flight of pest cockroaches might be expected in a hot NYC because they have a preferred temperature range which is between 75°F and 86°F. Below that temperature they will move to a warmer one if they can find it. Above 86°F they will try to find a cooler temperature. So, in a hot NYC the roaches will be climbing and gliding down to find that cooler temperature. In addition, in a drought they will be looking for water, particularly because above 86°F their cuticle lipids allow water to evaporate from their body much faster and they will dehydrate unless they find water. Hot temperatures and lack of water will keep the roaches jumping or they will die. That is why they have survived since they evolved 250 million years ago. Unfortunately they have staying power.

Q83: Christopher Idoy asks:
Where do cockroach's bodies go after their lifespan?

Ans: Christopher,
In nature, wild cockroaches that die of old age are usually on the forest floor under some leaf liter or under some loose bark. There the omnipresent bacteria and molds will degrade them relatively quickly and thus they are recycled. Most cockroaches do not die of old age. Most are eaten by a predator such as a mouse or shrew or spider.

The household pest cockroach may more likely die of old age and will likely dry up and grow some mold if not vacuumed up in the routine cleaning of the living spaces. If they die in a partition, their dried up bodies may accumulate if not eaten by a beetle larva such as a carpet beetle or silverfish or another cockroach. Eventually they will be recycled also.

More important is the question of where do their cuticles go when they molt and also when they die. If not eaten by the newly molted individual, the shed cuticle may crumble or be ground into the dust of a room. That cuticle contains the antigen that causes childhood asthma. That is one good reason to vacuum up the dust from carpets and floors so that the level of the cockroach antigen is kept low enough not to irritate the immature immune systems of children. It seems that the immature immune system can be hyper sensitized by the cockroach antigen and other household dust borne items such as dust mites. That is to be avoided.

Q82: Charlie asks:
Everytime there's a Cockroach in my house, and I'm about to kill it... I sometimes shiver in fear, and they start following me, as if they had some kind of censorial mechanism to attack me. In one of the cases, one flew towards me.
Can Cockroaches sense fear from, transmitted from, human bodies?

Ans: Charlie,
Your characterization of cockroaches goes beyond their capabilities as they are currently understood. As presented in my FAQ the cockroach is presented as fairly dumb. Their basic instincts are to seek our environmental cues in an established order: thirst > hunger > sex. Temperature of their environment fits somewhere in there. If their water needs are not satisfied their primary goal would be to find water which they can sense in a directional way. They can follow humidity up a gradient to a water source. When their water need is solved they would next seek out food, and so on ....
Sensing your fear is way beyond their capacity. If you are sweating due to fear, perhaps they could be sensing the water coming from your sweat and approach you to get water. The 'sensorial mechanism' in this case would be activated based on their water thirst.
Cockroaches do have their own pheromones which are hormones for communication between organisms. A fear hormone is talked about for mammals including humans but it would be a real stretch at this point to accept your characterization of the cockroach behavior you report as a sensing of your fear. I would eliminate the primal cockroach sensations as possible causes before I jumped to an as yet unknown sensory mechanism for cockroaches.
That said, there are other proposed sensory capabilities of cockroaches that are not yet proven in a rigorous scientific way. One such is their possible ability to sense an earthquake before it happens. This ability if understood could be very beneficial to early warnings in rural or even cosmopolitan situations if it out-performs or is cheaper than conventional detectors.
Similarly, a cockroach fear-sensor could be very useful if it could be calibrated and validated to reliably detect fear. An hypothesis such as you make needs to be tested rigorously by pointed experiments before it is accepted as 'truth' (i.e. not rejected).

Q81: Angelo asks:
I recently went to open my refrigerator door and sure enough, there was a roach inside on the refrigerator shelf. It got away, unfortunately, but made me wonder ... How?

Ans: Angelo,
Most refrigerators chill food to <40°F or 2-4°C. At 4°C pest cockroaches are inactive. They will not eat or drink at that temperature. They will be torpid. My guess is that the roach was hiding in the crevice of your frig door and dropped down into the frig when you opened the door. If it had been in the frig all the time it would barely be able to move and could not escape.

Q80: Yna Lim asks:  
What are the contents of a cockroach brain that makes it a possible antibiotic against MRSA and Escherichia coli?

Ans: Yna,
The brain is a very important organ in an animals life and survival. It fights all sorts of attacks from invading organisms and also anything that might disrupt its function.

All living organisms fight against microorganisms using whatever they are able to discover through the evolutionary filter of survival of the fittest. Ergo, we find an anti-cancer drug from the Yew tree's bark. There is not enough Yew tree bark to provide the amount of its anti-cancer substance needed. We have learned how to synthesize this drug without killing Yew trees.

For some reason, the cockroach brain has developed a unique general approach to antibiotics about which you seem to have heard. Insects do not have the highly-targeted immune response that we have, i.e. IgG, IgA, IgM, t-cells, etc. They have general responses to fighting against microbes. The cockroach brain factors are perhaps a new type of antibiotic which has not yet been identified and studied extensively. I have only read about it in news reports and the discoverers are keeping the details that they know somewhat close to their vest perhaps because they are in the process of discovery that is needed to apply for a patent. Also the criteria for publishing in a peer-reviewed journal are more stringent that those for reporting phenomena at a conference. They are perhaps playing the wise strategy of giving a little bit of info to the public to stimulate interest and perhaps private/public investment until they have enough info to publish in a professional journal or patent the technique. I am not sure what the British patent law is like vs the USA law. In Europe one can not patent a life-saving protocol. In America you can. In America you need to patent a protocol soon after you make the details public in a journal or you lose the right to patent. The most profitable approach would be to keep quiet about technical details until you to get a USA patent on the protocol/substance. For that reason we may not know the details of this story until the financial issues are settled. There are many such discoveries that never pan out.

However, if it is actually one or several new ways of fighting bacteria then understanding them could lead to new families of antibiotics that could be new treatments for the growing number of antibiotic-resistant-bacterial-strains such as MRSA (Methicillin-resistant Staphylococcus aureus) which no longer are controlled by their previously effective antibiotic.

Q79: Scarlet asks:  
We bought two female cockroaches about seven months ago, and ... one ... has recently given birth...? They are both ... female, and she gave birth about six months after we got her, which is too long for her to have gotten pregnant in the (pet) shop isn't it?! Even stranger is that she has given birth twice now (we think) but only to about three cockroaches each time.

Ans: Scarlet,
Cockroaches need to mate only once to produce up to 3 or more sequential batches (oothecae) of fertilized eggs. They store the sperm in an internal storage location and use it as needed. Sometimes the last batches of hatching embryos are small in number because the sperm was running out. Also the paired ovaries are made up of ovarioles which are strings of maturing oocytes. Only the terminal oocyte of an ovariole gets ovulated and fertilized to participates in a current ootheca. Sometimes the ovarioles develop tumors which then inactivates that ovariole from participating in a current or future ootheca. Sometimes if the female is not well fed and well supplied with water an embryo will die before hatching. Several phenomena contribute to how many offspring you will have. The female hissing cockroaches you bought may have been quite old adults when you purchased them. They do not show their age externally.
With fresh larvae hatched to rear, you can control their health and growth by how well you treat them. The males usually metamorphose to the adult stage first, sometimes an instar earlier than the females. Feed the larval males and females well with a low nitrogen diet. Mix ground dog biskit with corn starch to dilute the amount of protein nitrogen, moisten it with a bit of water and bake it into your own custom roach biskits. Too much nitrogen will give the cockroaches a form of gout, excess uric acid in their waste and their fat bodies. This gout can lead to an early death of your pet cockroaches. They are healthier if you feed them something like 10-15% dog biskit with 85-90% cornstarch. Give them a banana or carrot slice occasionally. Keep their container relatively clean and look at their fecal pellets to see if they have too much uric acid in them. They will be white if they have too much uric acid.
A healthy first parturition female Gromphadorhina portentosa can have 40-60 live offspring at each birth as you have read. Good luck.
PS: Virgin births (parthenogenesis) is known among cockroaches!

Q78: Scøut asks:  
I ... wonder if you might help me with (a) hypothetical: Say someone had found a cockroach that had been living near water and food contaminated by runoff from a golf course. It appears normal accept that it's roughly the size of a shoebox. How might you go about trying to explain such a thing? In your section on the Roach's size being regulated by its respiratory system and wondered if the two things might be connected?`

Ans: Scøut,
The possibility that a local phenomenon, pollution runoff at a golf course, could be the basis for the appearance of a 'hopeful monster' is an unlikely outcome. The concept of a 'hopeful monster', your 'shoebox sized cockroach', is not new and you can read about such phenomena, which was most recently described by the late Stephen Jay Gould. Find out about this phenomenon by googling 'hopeful monster'.

The runoff from a traditional golf course while perhaps not healthy for the surrounding environment is more a stimulus to normal growth, not a mutagenic event, which is what might cause 'hopeful monsters'.

The situation that the resultant overgrown cockroach was the size of a shoebox but otherwise normal would require a substantial genetic change. The change from a Periplaneta size (4cm) to a shoebox size (33cm) would have required the normal increase form stage to stage (1.25X the previous size) to be applied at least 9 times. One additional molt is not unusual in insects but nine additional molts would be very unusual and would need invocation of a 'hopeful monster' event.

Q77: Kelly asks:  
What other insects or arachnids are related to the cockroach? Are scorpions or lobsters?

Ans: Kelly,
Cockroaches are in the insect order Dictyoptera, which, to some, is a super order of the cockroaches, termites and preying mantids. In my mind, this is a firmly established group based on molecular as well as morphological and physiological evidence. I myself have published immunological evidence that the termites are like another family of cockroaches with the preying mantids being more distant from both termites and cockroaches. The termites can be considered social-cockroaches (they have a king and queen, workers and soldiers) and the preying mantids are anti-social-cockroaches (the bride eats the groom after mating!).

The cockroaches are also a member of an old-school ragged group of insects called the Orthopteroids which include grasshoppers, crickets, stick insects. This old group is based primarily on similarity in form and did not include the termites and mantids. This old school ignored the modern DNA and protein sequence data as well as physiological and internal organ morphology and physiology; i.e. it was 'really old-school'. The orthopteroids are certainly distinct from the 'modern insects' including beetles, bees and wasps, butterflies and flies. The orthopteroids are also more evolved than the so-called nerve wing insects including the dragonflies and lacewings and mayflies and dobsonflies. As basically winged insects, the Orthopteroids and all higher insects are more advanced than the wingless insects which include the silverfish and proturans.

No, the cockroaches are more distantly related to other insects and yet more distantly to other arthropods such as spiders (arachnids) and crustaceans (shrimp, crabs and lobsters).

But, recent evidence has connected insects more closely to crustaceans, which would make a cockroach more closely related to a lobster or crab or wood louse than to a spider. See this image from Science News Pancrustaceans-Sci discussion
Bjoern M. von Reumont, Ronald A. Jenner, Matthew A. Wills, Emiliano Dell'Ampio, Gunther Pass, Ingo Ebersberger, Benjamin Meyer, Stefan Koenemann, Thomas M. Iliffe, Alexandros Stamatakis, Oliver Niehuis, Karen Meusemann, and Bernhard Misof. (2012). Pancrustacean Phylogeny in the Light of New Phylogenomic Data: Support for Remipedia as the Possible Sister Group of Hexapoda. Mol. Biol. Evol. 29(3):1031-1045.

Q76: Sue asks:  
... In one of (your) FAQs, someone asked about roaches making sounds, and you replied that to the best of your knowledge the (pest species) didn't communicate through sounds.
However, one thing I noted at one point when my home was suffering a rather bad infestation of American roaches is that at night I would hear a clicking sound, very similar to the sound made when a person snaps a fingernail and thumbnail together. If I made this snapping noise with my fingernails, I'd get a chorus of "replies." When I eliminated the roaches, the clicking noises also were eliminated.
So although the evidence is a bit circumstantial, I believe that the American roach actually communicates via this clicking sound, perhaps a mating call?

Ans: Sue,
Good observation! That sound might fall within the realm of stridulation which I mentioned about some species of cockroach. One might ask how stridulation developed evolutionarily and it might have started with a few clicks of the roach wings or limbs against one another. Your experiment with inducing them to click is particularly telling. I would think that rather than mating, which has been studied fairly thoroughly, that the clicking might be a warning that is transmitted through the roach world. In certain species of the closely related termites the large headed soldiers do head-knocking behavior in their wooden galleries, banging their little heads against the wooden walls which sends an alarm signal to the rest of the colony.
Alarm-signal evidence in cockroaches would be an important finding. It would be further evidence of a social structure beyond mating much as white-tailed deer flash their tails or turkeys gobble a warning to fellow turkeys when danger arises. You may not be willing to recreate the environment in which the roaches were clicking and could respond to your nail-snaps but that would be necessary in order to design experiments to test your 'communication hypothesis'. Someone may read this in my FAQ and do just that. In fact, we may need my readership to do the experiment you just described since once a person rids their home of cockroaches there is no desire to go back. Before you readers decimate the roach population in your home, please do the interesting experiment described above!

Q75: Kevin asks:  
We are the producers of a commonly used household item. My question is this, we distribute product to off sight clearing houses (shipping consolidators). Recently we delivered a job to such a facility and they in turn got the product to the ultimate customer the next day. When the customer started opening the 20 some boxes he started finding cockroaches. By the time he had emptied the boxes he had found and killed ten roaches. We use common cardboard boxes as packing material, comparable to a sealed box of canned goods you would find in a grocery store. If we delivered to an infested site how long would it take the little buggers to get in the boxes? I know this particular job did not sit on their dock for more than 12 hours.

Ans: Kevin,
Cockroaches are active for the four hours after the normal 'lights out' in a building. Your shipment was presumably packed in the evening and sat in the dark, perhaps still somewhat open, at the end of business. The cockroaches became active and then after their four hours of activity they sought a hiding place for the coming day. Some hid in your packages and then were found upon eventual delivery the next day.

Q74: Tara asks:  
Growing up, my room was the only room in my parents house that cockroaches completely infested. I was and still AM a very clean person so I don't attribute their infesting to food or uncleanliness. I've had cockroaches drop on me in the middle of the night countless times, fly directly at me, fall on me in the shower, crawl underneath my pillow/couch cushion sit on my purse strap or inside my purse, crawl in my shoes/clothes, crawl in my drawers, etc. .... (Are) cockroaches ... attracted to my scent, is that possible?

Ans: Tara,
In 2005 scientists at Cornell and NC State, including my good colleague Coby Schal, identified the elusive hormone that attracts the male of Blattella germanica to the female. A news release of that discovery can be viewed at URL:

... so, due to some genetic anomaly you might be secreting that elusive compound, gentisyl quinone isovalerate. That is, if it is Blattella germanica males you are attracting. If you are attracting another species, you may be a living clue to identifying their attractive pheromone. Science advances in fits and starts. Serendipity is sometimes the most rapid approach to an answer.

Q73: Liz Jeavans asks:  
I would like to know how cockroaches walk up walls. I heard that they have statically charged feet, but is this true?

Ans: Liz,
Liz, The feet of insects including cockroaches are made up of a brush like pile which reacts with a surface like myriad weak suction cups. The weak forces involve adding together thousands of such individual adhering pillus ends and result in a strong enough force to suspend the body of a fly, a roach or even larger non-insectal critters such as lizards. To step the cockroach must remove the pilli individually in a wave, like ripping off some cellophane or an adhesive bandage. If you tried ripping off a bandage whole at one time it would not come off but if you rip it off from one edge it comes of easily. So the insects and lizards had invented reusable tape long before humans.
Here is a detailed URL on the topic:

Q72: Arlette Koiiman asks:  
I saw one cockroach with an ootheca when I caught it to throw it out.
My question is, where are the cockroaches most likely to place the ootheca?? Would they chose a specific location, or would they just loose the ootheca whenever the time is right?
Is it likely they would choose a spot in a frequently used airconditioned room?
Would they climb into the drawers or closet and chose to place it between your clothes???

Ans: Arlette,
Blattella germanica the German cockroach is the commonest small pest roach and carries its egg case until it hatches in about 18 days at 30C. At hatching the ootheca is on the female or dropped at random wherever she is at the time.

Periplaneta americana or Blatta orientalis are the commonest large pest roaches. They carry their egg case for a few days and then deposit it in a corner or crevice, cementing it there with local debris and saliva. A favorite place is in the corrugations of corrugated cardboard. They chew a hole into the cardboard and use the chewings to paste together over the ootheca that they have placed into the hole they have made in the cardboard.

They would not typically burrow into clothing in a drawer to do it. They might chose the corner of the drawer and use some of the lint available to glue together over the deposited ootheca.

Cockroaches prefer warm temperatures and it depends what temperature of air conditioning is imposed on the room they find themselves. Cockroaches prefer temperatures between 25 and 30C. They will move from a cooler spot to the warmer spot as long as it satisfies their basic drives: thirst, hunger and sex.

Q71: A. Ganesan asks:  
Does Cockroach like to be touched on all its sides? What is the word for it?

Ans: A.,
Thigmotropic. [Greek thigma, touch; as in thigmotaxis + -tropism.] This is a word used often in the plant world where a plant entwines itself about another object such as a vine climbing another vine or a tree or a string.

Cockroaches are thigmotropic in the sense that they like to conform to a hiding place during the day, conforming to a curve or having something touching them on top and bottom such as in a crevice.

Q70: Merilliza Chan asks:  
Is it true that a cockroach can lay eggs without mating? is that possible? o_o

Ans: Merilliza,
There are three issues here, egg laying, fertile egg laying and virgin birth:

1) Cockroaches and many other animals can lay eggs (infertile) without mating. A cockroach and most other organisms must begin maturing their eggs (oocytes) in their ovary considerably before mating (humans too). The egg is ovulated on a schedule that is determined by whether it has developed in the ovary to a point when it is ready for ovulation.

2) After ovulation, there may or may not be sperm to fertilize the egg that is ovulated. In cockroaches, if there are no sperm to fertilize the egg, the ootheca that covers the eggs is often thinner. The cockroach's physiology knows not to waste the protein on producing a thick oothecal covering and very often the female will eat the infertile eggs regaining the stored yolk protein lest it be wasted from the cockroach's nutritional economy.

3) Parthenogenesis is the process of producing fertile eggs without male participation. Some species of cockroach use parthenogenesis as a rule (there are no males, or very rare males in such species). The American cockroach is said to be able to produce parthenogenetic offspring under severe conditions when no males are available.

Q69: Jacques asks:  
Why is there not a single photo of cockroach eggs on the net? Well ok I saw 2 photos on google image but they were drawn or cr___y!

Ans: Jacques,

Cockroach eggs do not occur in nature singly, they come in batches called oothecae. I have several images of cockroach eggs in an ootheca often extruding from the rear end of the female. Try the following links.

Two families of cockroaches (Blattinae and Blattellidae) extrude the ootheca and hold onto it for a few day until they deposit it in a safe place to hatch about a month later.

Blattinae and oothecae

Nyctibora and ootheca

One genus of Blattellinae, Blattella, including our favorite Blattella germanica, the German cockroach, holds onto the ootheca extruding from its rear end until it hatches:

German cockroaches with oothecae

The entire Blaberidae family of tropical cockroaches incubate their ootheca covered eggs internally and you never see their ootheca unless you are someone like me who rears them and you see the ootheca during the extrusion phase after which they take it back into the uterus and incubate it until hatching/birth.

Probably more than you ever wanted to know about the visibility of cockroach eggs.

Finally, you would have seen more cockroach egg pictures on the internet if you had searched Google Image for 'ootheca' rather than 'cockroach egg'

Q68: 9513...@vmo... asks:  
What color are cockroaches most atrackted to?

Ans: 95...,
Cockroaches (and most other insects) have two light receptors, one sensitive in the ultraviolet range and one in the green range. Many insects also have a third light receptor peaking in the blue.

Most pest cockroaches are not attracted to light. They are active at night and if anything they might avoid light.

However, if you have a patio that is lit you might be asking what type of light should you have in your patio lighting scheme. The yellow 'bug' lights would be least visible to any of the wild cockroaches that can see light and fly and often are attracted to porch and patio lights. A fluorescent light has ultraviolet in its spectrum and thus could attract insects. A normal incandescent light will have the usual blue and green light in its spectrum and thus attracts insects that see that light.

The actual question of whether they are attracted to the light is another issue. Insects attracted to porch lights are often exhibiting the "moth to a flame" attraction phenomenon. Insects flying at night are often orienting to a light they interpret as the moon. If you are trying to fly in a straight line you might chose to keep the moon at a constant angle in your front line of sight. Since the moon is so far away, that keeps you going in a straight line. However if you mistake a porch light for the moon and keep a constant angle to it, you are likely to spiral into the light - like a moth into a flame. Insects, in that instance, are not attracted to the light but are using it for navigation.

Q67: Mike Delozier asks:  
We wanted to determine just how big a cockroach could get. Would the physiology and structure of the insect allow it to be as big as a dog or cat?   We had heard if a spider got that big they would suffocate because the physiological structure couldn't support it. Is there any similar restrictions with the roach?

Ans: Mike,
That is a classic question in insect physiology.

Insects are usually thought to be limited by the free diffusion in air of oxygen into their innermost tissues and free diffusion of CO2 out. Insects supply their tissues with oxygen using their segmental spiracular openings and the tracheal tubes that divide and subdivide until they reach the size of tracheoles which are small tubes that directly tangent the cell surface and gases exchange. This subdivision is such that the cross sectional area of the tube does not change at each subdivision. If the cross-sectional area of each tracheole at the cellular level does not change, it necessarily follows that as the insect volume increases, the size of the outermost tracheal trunk will needs be get larger in proportion to tissue volume. Given the properties of surface to volume, there is an upper limit to the size of an insect if the principles outlined are held constant. Extrapolated, the cross- sectional area of the spiracular openings would need to be larger than the available insect outer surface.

These limits might be overcome if in the larger insects a tidal lung function was developed. In some of the larger cockroaches there is a sort of tidal rhythm that occurs through the action of body wall muscles contracting and relaxing. This might extend the size of a cockroach by compensating for the need to maintain a constant crossectional area from the smallest to the biggest tracheae.

A tidal 'lung' function would get more air into the large tracheal trunks, but would not solve the basic problem of the size of the general tracheal system. I doubt that a single level of tidal 'lung' would allow the cockroach to get much larger than the current tropical cockroaches like Blaberus giganteus but it would be nice for someone to put a firmer theoretical basis on that limit. Good luck!

Q66: Wallace Anderson asks:  
... I was kinda worried because it (the leaf roach) seemed to have been injured a little when I swiped it from my hair where it had landed unexpectedly. ... Will it heal?

Ans: Wallace,
Good question! Actually I did my Ph.D. dissertation on that very topic. Cockroach regeneration of limbs. I wrote a chapter in a book on cockroaches on the topic:
Kunkel JG. 1981. Cockroach Regeneration. (PDF) Chapter 16 in THE AMERICAN COCKROACH, eds. WJ Bell and KG Adiyodi, Chapman and Hall, London, pp427-443.
The most common injury for them to endure is the loss of a leg. If a predator tugs on a cockroach leg it will fall off at a preset point called an autotomy point, similar to a lizard losing its tail as a reflex to being caught by the tail.
Unlike some other insects which will gradually regenerate a leg over several molting cycles, the cockroach will delay its next molt in order to regenerate its leg. This will provide the cockroach with the swift feet necessary to escape the next enemy quickly. Six legs are better than 5 or 4. The fast escape of the cockroach requires the pattern of running which uses a tripod of legs on the ground at any one time.
My Ph.D. dissertation dealt with how the cockroach delays its molting cycle in order to regenerate one or more lost legs. Yes, many slight to severe injuries can heal in cockroaches!

Q65: Mariele Pellecer ask:  
I ... wanted to know how do you sex them (Blattella germanica) before they molt to adults?

Ans: Mariele,
Since this is an important issue for cockroach biologists I constructed a page to explain it as I understand it from Mary Ross and Don Cochran, and have used this technique for decades. It is almost fool-proof:
Sexing Blattella nymphs

Q64: Karna and Izzy and Sarah ask:  
... we are moving. And we have a problem with big huge roaches in our house, mainly kitchen and bathroom.
I am VERY worried that during packing and moving the roaches will jump into my suitcases and nest in my clothes!!!!!

Ans: K, I and S,
What can I tell you? Cockroach larvae will hide anywhere they can. Moving with migrating human populations is exactly how pest roaches have gotten around the world. I have no magic solution. Kill the roaches any way you can before you reach your new home. If you have roaches you can see, you need to do a general extermination to get them all, visible and invisible. Fumigate the moving van? I am not an exterminator and have no special expertise in that respect.

Q63: Andy Robb asks:  
After cooking pizza in my microwave, I opened the microwave ... and discovered a small roach ... still alive. ... is it possible that it was in the microwave ... and ... survived?

Ans: Andy,

This experiment has been done often.

The microwave oven is amazingly non-uniform in its heating. That is why most of them have carousels to keep the food moving through the focus of the power.

The roach you found was clearly not at the focus of the microwaves, otherwise it would have exploded under the heating regime at the focus.

Q62: Frances asks:  
I wonder if you know of any roaches that have spiny protrusions extending from a slightly elongated abdomen that they upend and essentially point at each other when fighting.

Ans: Frances,
The cockroach species, Diploptera punctata, is found in Hawaii. It has cerci protruding from the tip of its abdomen and it will spray an acrid fluid from its upturned abdomen at attackers, usually not at each other but some small rodent intent on eating them.
Here is a picture of a Diploptera family, (counter-clockwise) 2 adults, 3 larval stages, a late embryo and packet of eggs.

Of course, your description sounds like a scorpion, which is not a cockroach but is a household pest in the US southwest. It also sounds like an earwig which has pincer like protrusions from the tip of their abdomen with teeth that are reared up in the air when they are disturbed.

You may be mistaken about the fighting. Mating male cockroaches extend their abdomen and point it at the female offering her a taste of a secretion on his abdomen. If the female feeds on this gland it stimulates the male to continue the mating process, eventually copulating and transferring a package of sperm to the female which then uses it for the next month or two fertilizing eggs.

Q61: Boomom asks:  
What is the little brown sac that falls out of some roaches when they are dying?

Ans: Boomom,
That is a sac of eggs, called an ootheca. See the pictures at URLs:
1) Blattinae, the Periplaneta family, with protruding and laid oothecae
2) German cockroaches, some females with ootheca.
The females carry the ootheca protruding from their bursa which is at their tail end until, depending on the species, it hatches, they hide it somewhere or until they retract it into their uterus to incubate it until the eggs hatch. The German cockroach carries it around until it hatches and might be the culprit you are specifically asking about. The American cockroach carries it around for a day or two until it hardens and darkens and then hides it in a crevasse covered with some camouflage they glue in place with saliva. The ootheca is only gently held in the bursa and could easily fall off when the roach is roughly handled or dying.

Q60: Elizabeth Palmer asks:  
How much weight can a cockroach carry? For instance, an ant can carry it's own weight...

Ans: Liz,
That saying about the ant sounds just as offhand as what I might give for the cockroach, but for an important difference: The ant is a forager which is designed to find and carry objects back to its colony nest. Carrying things has a meaning for ants based on their innate behavior.

The cockroach does not move things more than a few millimeters when it lifts things that it is nibbling while eating or tasting. Therefore the carrying question is meaningless in most situations. Cockroaches were not designed to carry foreign objects around.

The ant can probably carry things twice its weight. ... This is a perfect question for an undergraduate lab, but not particularly interesting to an insect physiologist. It would engage the student in trying to get the cockroach and ant to carry something. The student would hopefully learn that the ant instinctively carries things off and the cockroach does not. This exercise would teach that the posing of a logical experimental question is an important step in doing research.

A close relative of the cockroach is the preying mantis which catches and lifts other insects to eat them. The females will even catch and eat the male after she mates with him. The male in mating with the female, jumps on its back and is carried around during the mating process. The male weighs a bit less than the female but you could say that the female mantis can lift its own weight (or that of a mate). In this case the female does carry the male on her back while mating, then she grabs him and eats him on the spot, usually without carrying him any further.

Similarly the other close relative of the cockroach, the termite, is a social insect which lives in a nest but it does not go foraging and bring back large objects the way that an ant does. The termite can forage for bits of wood and does lift bits of wet saliva soaked wood in order to extend its nest, often building huge structures in Africa, or, more close to home, tunnels from house siding across foundation to ground. Carrying of this building material is essential to survival for these termites.

The cockroach female does not carry the male on her back during the mating process as the mantid and many other insects do, they mate tail to tail with no carrying involved. So, you need to create a question about cockroaches that has meaning. A carrying question about a cockroach is not meaningful, unless you could create a situation in which it needs to carry something. When a group of cockroaches is very hungry I have observed them competing for food. Occasionally I have seen a cockroach drag a piece of food off to nibble on it without being harassed by close neighbors. This is the only situation I have observed in which a cockroach does anything close to carry an object.
Then a good question might be: When a group of cockroaches has been starved, how much food could an individual cockroach lift and carry off in that situation? I do not know the answer.

Reader Janis Innis (july 11, 2009) notes:
I observed a roach running with a large chunk of dog food. It was running across the kitchen, but when I entered the room, it turned and ran back towards the other side of the room. I would estimate it covered six feet while I was watching it. I would guess the dry dog food chunk weighed much more than the roach. ....

Q59: Jennifer Manley asks:  
I have an insect that I believe to be a Blaberus colloseus, just judging by the one picture I could find on the internet. Can you tell me where to find out anything about this guy? I'm not having any luck on the internet.

Ans: Jennifer, My experience with Blaberus species is limited to B. giganteus, B. discoidalis, and B. cranifer. Now that other species of Blaberus are becoming attractive as pets and feeder cultures worldwide, our poor understanding and literature about the diversity of species in this and most other cockroach genera is becoming obvious.

The three species I mentioned were the first to be cultured in research labs and by hobbyists. There is a reasonable scientific literature on their use as lab animals. We actually know little about their natural ecology and behavior except where experimentalists and hobbyists have taken the time to describe it.

I have no information and could find no information at PubMed or Web-of-Science on Blaberus colloseus the "Ecuador roach" or Blaberus colossus, the more likely spelling. It is also possible that this name is a synonym or a mistake that you have run across on the internet on the many hobbyist pages dealing with cockroaches.

One note of caution, many Blaberus species look alike and if you have collected your Blaberus species in the wilds of the southern USA, it is most likely B. discoidalis or B. giganteus which can be found in the wild on our southern USA coast.

Q58: An editor asks:  
I'm a freelance editor on deadline trying to edit a story on roaches for a reading textbook .... (T)here is so much conflicting information on the web. ...(C)ould you clear up the following ... questions for me?
(1) How many nymphs can a female German cockroach produce in a lifetime (how many eggs per sac x how many sacs)?

Ans: That number is not the usual number quoted and is (~40 x 5-6) = 200-240. In my substantial experience using B. germanica in my lab, a single female can produce at max about 5-6 egg cases during her lifetime, each about a month apart after her own approximate 35 day juvenile phase. The timing depends on temperature and they develop most quickly at 30C. Each egg case has approximately 40 eggs so that means a single female will only produce 240 primary offspring. However most people like to scare you with the calculation of total progeny. That means understanding that only half the 240 primary offspring are females who could each also have 240 offspring half of which are females. Depending on the temperature one needs to calculate the larger number of offspring that a female can produce in a year, which is the usual number that is quoted.
(2)Same question for American cockroaches?

Ans: The American cockroach produces 1 ootheca per 2.5-3 days with each ootheca bearing about 12 offspring. The number of ootheca in the adult life of an American roach is probably somewhere in the literature. The egg cases start being less frequent as the female gets older and some of the ovarioles become inactive such that an ootheca might only contain 6-8 eggs in later life. I presume an adult female might continue the output for 6 months (although that is a guess) so resulting in 60 ootheca x 12 = 720 offspring. The variance about this average might be quite high so I would not be surprised by actual counts of females producing 500-1400 offspring in her lifetime.

Q57: Rochelle asks:  
I see that you've mentioned that cockroaches are connected to asthma in kids. Please could you explain this to me? Why do they cause atshma?

A: Rochelle, You ask a good question. Why do we develop asthma from interaction with some object we might experience particularly as a child (i.e. childhood asthma)?

Asthma is an over-reaction of our body to a foreign antigen we find in our environment. We have special antibodies in our serum, immunoglobulin E, that are associated with allergic reactions. When we develop an allergy to something in our environment that allergic reaction sometimes takes directions that are dangerous to the individual. A severe reaction is anaphylactic shock which can kill you. A milder reaction includes various levels of asthma.

Why do children develop asthma by growing up in a cockroach infested home? Young children crawl around on the floors and carpets which may have the parts and proteins of cockroaches imbedded in them. The same goes for pet dander and allergies to dogs and cat dander. When an allergy test is given to those asthmatic individuals they find the children react perhaps to cockroach antigen and perhaps to dog or cat dander antigen. Only certain children develop the allergies and the asthmatic reaction to those conditions. This seems to be partly an inherited tendency, so, allergic parents may pass on the tendency to become allergic to their children. Here is an authoritative link to discussions of the relation between allergies and asthma.

Q56: Glesne asks:  
How fast are cockroaches?

A: Glesne, Cockroaches are fast enough. They have giant fibers in their ventral nerve cord that transmit the sensory info from their cerci, which sense air currents, directly to their thoracic ganglia which control their leg muscles. This is a reflex circuit which does not need any decision by the cockroach brain.

It is fast enough to detect the air wave in front of a predator and allows the cockroach to scuttle away, avoiding capture. If you want to know how fast in cm/sec you will have to do your own experiment. Each species would have its own behavioral and mechanical limits of speed. You might make your measurement of speed in terms of body lengths per second which might allow you to compare species of cockroaches.

What would be your measuring conditions? Starting from a full stop and measure speed after 0.1 or 0.2 seconds? You have some thinking to do before you can decide how to measure the cockroach speed. How long can a cockroach maintain its top speed? How long does it take to accelerate to its top speed?

Q55: Justin Winstead asks:  
I had a debate with my brother and his wife over whether or not cockroaches live in organized groups. I said that they do live in organized groups and they acted like I was crazy. Can you set us straight please?

A: Justin, Social structure in the cockroach pest species is next to invisible. However there are a few indications of group organization. Most such behavior would not be considered social:

1) Many cockroaches care for their eggs until they hatch, including the German cockroach which carries the eggs externally until they hatch. A whole Family of cockroaches, the Blaberidae with subfamilies Blaberinae, Zetoborinae, Epilamprinae Diplopterinae and Pycnoscelinae among others, carry the eggs internally until they hatch. One Blaberid species, Diploptera sp., provides nutrition to the embryos which actually molt in utero several times such that they need only molt three times after they are born to become adults, URL: D_punctata-devel-2864.JPG

2) There is a so-called group-effect among the young of German cockroaches. If they are alone they develop very slowly. If there are at least two larvae in a defined space they accelerate their development to become adults. This later behavior is a mechanism that increases the probability that two adults will be present by the time adulthood is reached. Unfortunately, this effect is sex-neutral so the two adults could be both males or both females with a probability of 50%.

3) The termites are a group of insects that have approximately the same level evolutionary relationship as Families of cockroaches. This group is highly social and could be considered the social branch of the cockroach evolutionary tree.

Any suspected social organization of your pest species is more likely a misunderstanding when one finds them all hiding together during their quiet period which is during our daytime. Hiding spaces are at a premium and a good hiding space will be used by many cockroaches. Is sleeping-together "living in organized groups?"  Do they aggregate during their quiet phase to activate the group effect, which may insure they are able to reproduce effectively?

Q54: Laurie Betts asks:  
Are there Australian cockroaches in the USA?

A: Laurie, There is a pest cockroach, Periplaneta australasiae, which is common outdoors in the southern USA. It is commonly called the Australian cockroach. It is found worldwide as a pest and also called the greenhouse cockroach because of its predilection for establishing itself as a pest in the warmth of greenhouses at all latitudes. It is also found in western Australia. I am not sure of the etymology of the common name, 'Australian cockroach'. The actual geographic origin of pest species is not easy to determine. North Africa seems to be the major focus of the wild species of the genus Periplaneta, thus Periplaneta americana is thought to originate in North Africa despite its common name, the American cockroach. It is thought that the pest species of cockroaches have dispersed around the world with the, relatively recent, early human migrations, explorations and trading activity. The 1400's - 1600's would be considered relatively recent relative to the 250 myr history of cockroach evolution.

The scientific name is P. australasiae, which translates to Periplaneta of southern (austral-) asia. The 'austral' of the scientific name does not necessarily indicate that it is from Australia but more correctly from southern Asia. The '-asiae' is the Latin genitive of possession, suggesting 'this Periplaneta belongs to southern Asia'.   'Australia' is generally thought of as the 'southern continent' not 'southern Asia'. The scientific, Latin names of insects and their common names, if common names exist, are often applied for local or mistaken reasons. Somehow, the common name 'Australian' was applied at some point in time to P. australasiae. See URL:

There is another answer to your question. The cockroach Family group, Polyzosterinae, is almost entirely found in Australia, thus it could be thought of as a group of Australian cockroaches. It has hundreds of described species, most if not all wingless as adults. There is one species of this Family in the USA, Eurycotis floridana. It is thought that E. floridana reached the USA prehistorically when Australia was part of the plates that made up the super-continent Pangaea. During the separation of Australia from South America, about 50 myr ago, it is thought that the then nuclear Family of which Eurycotis was a member split, sending one or a few representatives up into South American landmass and the remainder in the future Australian landmass. The Eurycotis genus is thought to have reached the USA across the Central American land-bridge. Eurycotis floridana is the only surviving species of the Polyzosterinae in the USA while the Polyzosterinae blossomed in Australia. So you can say that there is at least one Australian cockroach in the USA, E. floridana. ... or two if you include P. australasiae.

Q53: Kian Hwee (Singapore) asks:  
... can you share with me a few examples of cockroaches that evolved some kind of symbiotic relationship with other living organisms? Thank you.

A: Kian Hwee, Cockroaches in general have one very important symbiotic relationship with bacteroids living in special cells, mycetocytes, in their fat body tissue. The bacteroids are passed from generation to generation as a thin coating on their eggs, between the chorion and the oocyte cell membrane. During embryology these bacteroids invest in the female future ovary and the developing fat body tissue. The bacteroids produce all the vitamins needed by the cockroach with the exception of choline and cholesterol which remain as the only essential vitamins of the cockroach. The close relatives, termites and preying mantids have lost or never gained this type of symbiont. They must get their vitamins, like Vit A and D, in their food.

This is a true symbiotic relationship since the cockroaches have protected the bacteroids over the millions of years of their association and probably these bacteria-like organisms have been protected from changes forced on their strains by mating with other bacterial strains and have remained true to their type since they accepted the cloistered life they enjoy in the cockroach fat body. As long as the cockroach survives, these bacteroids will survive. They have hung their survival on a pretty sure bet. How is that for a symbiotic benefit?

The cockroach makes out pretty well also since due to the vitamins supplied by the bacteroids, the cockroach can eat almost anything organic without thinking of whether it has vitamins and essential amino acids, which we all need to get via our diet or a vitamin pill!

Q52: Mendriks asks:  
How would we know a cockroach was still alive if it does not move? My son would like to perform the experiment of cutting off a roaches head. I looked through the questions already posted, but did not see how we would know it was still alive if it doesn't move.

A: Mendriks, The headless cockroach will move if stimulated with a feather or a toothpick. The cockroach will sense an irritation on its leg or back and move to avoid it if it is still alive.

The way to do the experiment with the greatest chance of success is to take some old-fashion dental floss, the type made up of very fine filaments and make a simple loop knot that is put over the cockroaches head and drawn tight around its neck. You can also use a fine silk thread or hair from your head and similarly make a loop knot that can be tightened. At that point you can cut the head off on the head-side of the knot. This prevents the cockroach from losing any blood. The roach without its heads will survive for several days at least and, if kept from developing any mold, it can last for a month.

Without the knot the experiment will work but if you disturb it too early, before a blood clot is formed on the wound, the cockroach will expel its innards through its neck and die thereof.

Q51: Robert asks:  
I read here that the cockroach can live for about a month without its head.   Is it possible for a female to be headless and get pregnant by a male and give birth before it dies?

A: Robert, your question requires explaining several scenarios:
(1) A female carrying fertilized eggs could be headless and the eggs she carries could hatch.
(2) Females also store sperm and can fertilize several subsequent egg packages (oothecae) before they need to mate with a male again. However, a cockroach female needs the head associated gland, corpora allata, to produce the reproductive hormone, JH, to produce a batch of eggs and produce the pheromone that attracts a male to mate. Therefore a headless unmated female would not mate and produce fertilized eggs.
(3) Whether a mated female with ripe eggs who loses her head could ovulate the now mature eggs and hold onto them until they hatched is questionable. I am not sure if we know the answer to that question. I do know that I did take the ovaries out from of a female German cockroach that was half-way through her ovulation of eggs. The eggs continued to be ovulated in the physiological saline that I was observing them in. I do not know if the other organs that put the oothecal covering over the eggs would have functioned properly. This would be a simple experiment to confirm using the synchronized batches of mated females that I have used previously in my experiments, URL:
(4) In Blattella germanica, the German cockroach, the ootheca is held by the female for about 18 days before it hatches. The female provides moisture to the ootheca which the female carries protruding from her bursa. It is precisely the moisture that she provides the ootheca that is in short supply when her head is severed. I doubt that a female which has lost her head and just ovulated her eggs could bring those eggs to term and hatching given the inability to provide water. In a moist atmosphere perhaps it would be possible.
(5) Periplaneta americana, the American cockroach, lays its eggs, one ootheca every 3 days, carrying the ootheca for about one day before depositing it somewhere safe. If such a female lost her head prior to dropping the ootheca then I am not sure whether the ootheca would be dropped but it is entirely provisioned with enough water to last until it hatches.
So, your question's answer has several stages of possibility. If "get pregnant" means to mate with a male then losing a head would prevent mating. If a female has already gotten to the stage when she has released her sex pheromone to attract the male then a male would be attracted but the female must exhibit some requisite behavior, requiring the head, when a male presents himself to mate with her. Without its head it would not accept the male's mating overtures. But if a female was already mated before her head was lost and "get pregnant" means the ovulation and fertilization of the eggs by the already acquired sperm, then the above discussion does not absolutely preclude her producing and hatching some eggs. Carried eggs might well hatch, unovulated eggs might ovulate and be fertilized but whether they would acquire the requisite oothecal covering to reach hatching is experimentally unknown at the moment. That is a good question.

Q50: Roland asks:  
My 9 year old son came home today telling me that his science teacher told him that cockroaches were being used in large farms to produce methane gas. I had never heard of this. Any truth to it?

A: Roland,
Your son may have access to some information of which I am not aware. The practicality of methane production by cockroaches is not established as far as I know.

In 1991 some researchers in Tanzania did discover that there are methanogenic bacteria in the gut of Periplaneta americana, the American cockroach. Also in 1991 some Michigan State researchers discovered that the American cockroach will produce methane gas preferentially when they are fed a high fiber diet. These publications were part of a flurry of publications about methane production by cockroaches in the early 1990's. You can find these publications by using Google/Scholar:

... and searching on: methane cockroach.

I have not found that these facts have been commercialized into farms for the production of methane. Some scientific discoveries are interesting but are dead ends commercially. Small businesses however often go bankrupt because of poor planning and management; and perhaps the underlying ideas are still sound. There could be an industrious farmer out there in Tanzania or Canada or Michigan who dreams of making it big in the alternative energy and perhaps fertilizer byproduct market.

Q49: Timothy Ampi asks:  
Does cockroach have emotion (fear, anger, happy)?

A: Timothy,
Emotion is not usually associated with insect or cockroach behavior. The cold and unmoving surfaces of the insect exoskeleton do not allow for movement of surface muscles and skin that one can interpret as a smile or other facial emotion. Insects react to environmental cues with reflexes that we usually do not interpret as emotion.

Have you ever seen the waggle communication of the worker honeybee? It is used to communicate the direction and richness of a nectar source. That is interpreted by insect behaviorists to be a reflex behavioral response released by finding the nectar source. The public might interpret it as an indication that the worker is happy at finding the sweet nectar. Go figure? Is there any evidence that the bee is happy? What would that evidence be?

Is a bee worker angry when it stings an intruder to the hive? We subjectively use the terminology "angry worker bee".

Now, is there any behavior that you might ascribe to something you see a cockroach do? Is their escape behavior based on fear? Or is it a 'simple' reflex?

Science would suggest it is a simple reflex in all the above cases of insect behavior. Our emotions (e.g. happiness) are associated with the release of certain chemicals in the brain (endorphins) which also have been discovered in the insect brain. Does that mean that insects feel happiness? Does that mean that what we call happiness, endorphin release, in humans (or mice) is a reflex?

These are difficult subjective questions that science rarely deals with but are fun for us to think about. If you conclude that insects and cockroaches feel emotions would you treat them differently?  Read the poem St. Roach by Muriel Rukeyser.

Q48: Martha Johnson asks:  
I am interested in some type of roach control that is safe and non-toxic for myself, an invalid, and my companion dog. We live in coastal Texas with high humidity and a leaky roof. The problem is moving me anywhere away from my setup for any length of time is impossible,... and my dog loves (to eat) cockroaches. I used the Bengal product which worked for a while and also spread borax.

A: Martha,
I was involved as a consultant in the development of a Metarhizium anisopliae product which uses a bait station dispensing a mold that is lethal to cockroaches (but non-toxic to vertebrate animals and humans), rather than a chemical poison. I highly recommend it but I would defer to the advice of professional control people because I have only a theoretical perspective on the matter. The Metarhizium anisopliae bait stations might have to be applied periodically if the mold dies out due to a lack of critters to pass it on. The boric acid, not borax (a different compound), should not be dangerous to your dog if used in small quantities as a dusting in isolated corners where your dog would not reach to sniff it into its lungs. Chemical safety bulletins are typically alarmist (e.g. Baker) and warn of respiratory damage and irritation if inhaled. A large amount (grams) needs to be ingested to be lethal. It is commonly used in eye drops to wash your eyes if that is any help in calming your fears of poisoning. Some concern is voiced about constant exposure. It is not a poison in small quantities and should not be spread in large quantities. People often feel that "if a small amount is good, a lot will work better". In this case a small amount is good but a large amount could be dangerous. Also boric acid is said to act in its dry form to abrade the cuticle of the cockroach so that it dies of water loss. This might not be very effective in your situation where there is abundant moisture that could dissolve the applied boric acid and thus make it ineffective as well as your leaky roof providing plenty of water to the roaches which would also save them from desiccating. These two solutions to roaches should not require that you or doggie companion to be moved out of your setup during their application as they are both non-toxic to vertebrates if applied in moderation.
In my experience, 75% of your problem is the excess moisture. Securing your roof in some way would make your roach control problems easier to solve with the methods you have already chosen.

Q47: Alexandra Manou asks:  
What is the cockroach reproduction cycle? ... Was told by pesticide company that it is 40days, including winter. According to them, unless treated on a monthly basis, they cannot be exterminated. Is this true or an excuse for frequent visits?

A: Alexandra,
The reproductive cycle like the life cycle depends on the temperature. It is maximum for most pest species at 30ºC which is about 86ºF. At that temperature an egg case is produced by _Blattella germanica_ adults in about 6 days but it is held by the female for 18 days before they hatch. The other common pest species, _Periplaneta americana_, deposits an egg case every 3 days at 30ºC and each egg case will hatch in about 30 days. Perhaps that is the magic number 30 that corresponds to the lunar monthly cycle that your exterminator has suggested is critical for visits.

The rates of egg production and development are temperature sensitive so at 25ºC all the above times are approximately doubled, slowed down by the reduced temperature. Another 5ºC reduction again doubles the times and thus the German cockroach egg laying and hatching cycle would be quadrupled from 24 days to 96 days.

Most homes are cooler in the winter than the summer so roaches are probably growing and reproducing slower in the winter than the summer. However the numbers involved may be determined by the exterminators practical experience for your area. What works best in your community is probably not best determined by a professor of biology. For instance, the outdoor cockroach refuges that provide the reservoir of pests that would enter your home may be the determinant. In cities, the sewer system may be the major reservoir of cockroaches and it is the temperature there that possibly drives the infestation rate. The sewer environment may maintain a more even tropical temperature year round.

Q46: Thomas Coxey asks:  
Where did the cockroach get its name?

A: Thomas,
Pest cockroaches have lived with people of many cultures perhaps before language developed. Here is a link to the common names given to cockroaches in different cultures:

Some common names have some suggestive associations. (1) Water Bug. (2) The German cockroach, Polish cockroach, Russian cockroach, Crotton bug all refer to the same species Blattella germanica because one community wanted to name it after something they despised. (3) Some dominant societies have named their local pest cockroach after their oppressed native population. This practice is a sad reflection of how far prejudice has driven our common language.

Our common name 'cockroach' shares sounds with Dutch 'kakkerlak' and Spanish 'cucaracha' and the Spanish song 'La Cucaracha' brings to mind vigorous stamping of the flamenco dancers feet which could refer to the canons of war ... or the stamping feet of a homeowner on the pests. I am told by a reader that the song has multiple potential meanings. The origins of the names are entwined in early cultural history and only careful etymological and sociological study might discover the origins of our word 'cockroach'. I am not aware that such research has been successful in this case.

Q45: Frank Melchior asks:  
I have a question. ... Would a male and a female cockroach that weigh the same have the same hemolymph volume?

A: Frank,
Larval males and females of the same size have the same hemolymph volume. Last instar females are bigger than last instar males, anticipating the larger abdominal format of the females and tend to have more hemolymph.

Adult females are generally more robust than males particularly in the abdomen where the ovaries of the female take up substantially more volume than the adult male gonads. In addition the fat body of the adult female is much more developed due to its involvement in vitellogenin synthesis in support of egg development. Coincident with this greater abdominal tissue development there is more hemolymph in the reproductive adult female.

Finding an adult female the same weight as an adult male might be difficult. The largest adult males and the smallest females might be the same weight and perhaps they might have the same blood volume but I doubt it. The females more extensive abdominal tissues are all laminar and would require more volume of blood to suspend them. I hypothesize that if you measure male and female blood volumes the adult females would have a larger blood volume when regressed against weight due to their greater tissue surface needs.

Q44: Katherine McGlothlin asks:  
What was the reason for this cockroach behavior? On Sept.29 around 9:00 pm in my front yard ... I observed a large number of cockroaches (maybe 100-200) pouring out of a manhole. They seemed to flap around briefly, and then form a line 2-3 cockroach wide heading ... towards a large tree. Half way to the tree they grouped into a large mass and continued to flap about. It almost seemed to be a mating frenzy. This sight, ... was observed by the light of a full moon, was ... interesting and also creepy.

A: Katherine,
I am not particularly a behavioral expert but I have seen such a frenzy in the lab on a smaller scale when I added a bunch of mature adult males to a bowl of virgin adult females who were all ready to mate.
What you observed in the wild does sound like a mating frenzy. The population pressure in the utility/sewer was probably pretty high. One or more females were probably sending out sex pheromone signaling that they were ready to mate and they were being mobbed by males who were ready to mate. The flapping of wings is the males' signal to the female that they are ready and the males would pursue the females and occasionally bunch together around what they sense was the source of the pheromone. The females would respond by palpating the abdomen of the male she chose to have sex with and if she was really ready she would copulate with the most 'attractive' male.
I do not know how common the mobbing phenomenon is but I expect it often happens down in the sewer as long as the population pressure is not high.
I also would assume that it was only adult cockroaches that participated. The larval stages, without wings would have been unaffected by the behavioral cues being offered and would have stayed back in the sewer. This behavior might have the purpose of getting the adults in a crowded population to disperse before they mate and produce eggs. A close relative, the termite, exhibits this adult mating flight swarming quite frequently. It is interesting that you may have stumbled on observing one of the traits that link the two groups (termites and cockroaches) from a behavioral point of view.

Q43: Cressida Mahung asks:  
How can I tell if a cockroach is breathing?  How do I measure the breathing rate?  I would like to do project on this for my science fair, but I am stuck!

A: Cressida,
The cockroach's breathing rate, like that of most insects, is controlled by accumulation of carbon dioxide, not lack of oxygen.  In order to conserve water the average insect closes its spiracles, which are the openings of the insect tracheal system that supplies oxygen to all tissues and removes the carbon dioxide. When the carbon dioxide in the animals system rises to a critical level, the spiracles open and then CO2 leaves the system and oxygen enters. In most small insects this opening and closing of the spiracles (breathing?) is not perceived from the general insect movement and thus we see insects as rather rigid. We see no obvious breathing.
If you however look at breathing as the uptake of oxygen from the available volume of air you could measure this disappearance of oxygen as volume of gas. I have done this in a student laboratory using an apparatus similar to the diagram below, a small vial with a stopper in its end through which a breathing tube is inserted:


If you put an animal in the vial above and keep the vial in a constant-temperature water-bath then the water will enter into the small tube that goes through the stopper and the water will continue to be drawn in through the small tube as oxygen is used up, somewhat like the mercury in a thermometer. CO2 dissolves in the water and is thus removed as it is expired by the insect and thus the volume declines as oxygen in the air is used up by the respiring insects. By measuring the position of the water in the tube you can measure the usage of oxygen. This is the long accepted method of measuring respiration of such small animals.
You could also restrain the insect under a microscope so that you could watch the spiracles and watch them open and close. However, a restrained insect often struggles and its use of oxygen will go up abnormally. Some minimal restraint might be designed such as gluing the pronotum to a wand and giving the insect a small light ball to "walk" on. The wand can be maneuvered to allow the abdominal spiracles to be observed by a dissecting microscope, allowing the spiracular opening rate to be counted.

Q42: Joe Rowell asks:  
I am a illustrator going to Savannah College of Art and Design and I am trying to illustrate a image from a roaches point of view. What would that look like?

A: Joe,
You would be looking out of a crack at the world during the early morning or during the day in a half stupor because you would be hiding there sleepy or asleep from 2AM to 10PM. At 10 PM when the human household turns off the lights you would come to life and be looking at the world from weird angles since you would be scuttling on the floor or viewing the room in dim light from standing on the wall or the ceiling.

Q41: Alejandro from the Phillipines asks:  
... I have observed that cockroaches in my house get "wild" before any earthquake occurs. They start running and getting out from their niches. ... I have the impression that cockroaches can "feel" some of the very early vibrations of an earthquake, small or big, and can be a very good help to give "early warnings" of earthquakes. Can you confirm this?

A: Alejandro,
If you have done a careful experiment to demonstrate the phenomenon you should publish it. There have been newspaper articles professing to demonstrate that point (perhaps 20 years old) but I have never seen confirmation of earthquake prediction by cockroaches in the scientific journal literature. The type of proof that would be needed is a type of automated or regular observational record of the cockroaches and the demonstration of how that record changes and predicts future seismic activity. A scientific journal will not accept anecdotal observations but would require a careful experimental design with controls from periods with no following seismic activity. Reliability would be another issue. Do the cockroaches predict every earthquake? Are there times they produce a false positive, i.e. their activity predicts a quake that does not happen?

A better approach would be to build a small chamber that would act as an activity meter which would automatically record the cockroach activity. There are several designs for a cockroach activity meter. One that might be useful is a small light plastic pie plate with lid. It would sit on a metal base that would conduct electricity. The plate would sit on a pin at its center that keeps the pie plate off the metal base except at one point on its rim. A large cockroach such as Periplaneta during its normal activity cycle would make the pie plate rotate on the metal plate as it walks around the plate. A wire at one or more places on the rim would make a circuit and that circuit closure could be recorded with its time of occurrence. This activity rhythm (because cockroaches are normally active for 4 hours after lights go out in the evening) recording gives one a record of the normal activity something like the following:

|||                                 ||||||||||                              |||||||||
0                    12                   24                   12                 24
Midnight            Noon               Midnight               Noon             Midnight

Then your seismic event might look like:

|||         || || |      X          ||||||||||                              |||||||||
0                    12                   24                   12                 24

... which predicts a seismic event at X, about 13:00 or 1PM.

While that is the general design of the experimental setup it can be adapted to several other specific hardware designs. For instance the analog design described above could be changed to a sold state and digital design by using a digital camera or camcorder to take a digital image of the cockroach in its dish which would record if it has moved since the last picture. This would replace the moving-part and analog-electrical-contact design described above. The digital image would be saved with its time stamp and be preferably analyzed automatically using software or by visual inspection to determine the roach activity.

I understand that these approaches might be beyond your technical capabilities but that is why we have research labs at universities and commercial labs that do this type of sometimes expensive basic and applied research. Such designs, once proven in the lab, possibly could be commercialized and be able to be packaged with computer software as a seismic prediction device which could be located in a local prediction center or police station where a perhaps automated warning could be broadcast to the public.

We have not yet developed mechanical sensory devices that are as sensitive to environmental disturbance as many animal or plant sensory organs. This area of research has been dubbed 'biosensors' and grants are available to pursue such questions. Ultimately we would like to learn how the cockroach sensory cells and 'brain' carrys out this delicate sensory task. Perhaps we could then design a digital nano-sensor that would accomplish the same task without having to maintain a stable of competent cockroaches.

Q40: Marlene asks:  
A former science teacher said that cockroaches glow under black light. Are they flourescent?

A: Marlene,
I have never seen a cockroach glow under black light however another arthropod more common in more tropical or desert regions, the scorpion, does glow fluorescently.
Scorpions are well known for this phenomenon. Their generally soft cuticle has fluorescent compounds. There is a famous picture on the cover of Science of a fluorescent scorpion. I once took a walk in the evening desert outside Albuquerque NM with a portable black light. The cresote bushes, after dark, illuminated with black light became like Xmas treess illuminated with scorpions which were foraging for prey on all the twigs and branches of each bush. It was a powerful demonstration of how physically active they become at night and just how many scorpions are out there.
Perhaps some cockroach species would show some flourescence but I have never seen it nor heard of it from any other experts.
Link to abstract on this topic

Q39: BEH301 asks:  
How do Cockroaches Digest and what organs do they use to do so?

A: BEH301,
You can look at the diagram at URL: ... This is an illustration by GEORGE ROLLESTON published in 1870.

Cockroaches shred food with their mouthparts and then swallow it using their salivary glands (e) and salivary reservoir (f) to moisten their food before it enters their crop (d). Their gizzard or proventriculus (g) grinds the moist food further and adds it to the stomach (i) into which digestive enzymes are poured from the gastric caeca (h), after which it flows into the intestines (l) which is shown separated from the tubular stomach by a short segment of the peritrophic membrane (k) which is a chitin sac woven by the microvilli of the stomach to contain the bolus of food which passes through the GI track. The hind intestine (lower-l) removes water from the digestate and then the rectum (m) compacts the remains into a roach scat. The digested food is relieved of its nutritive materials by the walls of the stomach and intestines.

Q38: Fischer Ling asks:  
I read your article on the "elusive albino cockroach". Just hope that you can provide me with more insight on the following (3) questions:
Q38.1: Is it scientifically possible for a albino cockroach to mutate in the wild naturally? Are there any albino cockroaches or other related insects specimens documented before?

A1: Such mutants are possible but the hardness of the cockroach cuticle depends upon the tanning process which cross-links its cuticle with a process that creates a mahogany-like color. Thus an albino cockroach (or other naked insect) would have weakened cuticle which would make it very vulnerable to attack.
In insects clothed in colored hairs or scales the color of the scales can become white due to the storage of white substance in the scales. In this sense the underwing moth, Catocal relicta, has an albino morph which is able to hide on birch bark trees based on its ability to hide on the cryptic bark surface, URL:
Albino examples such as the one above are relatively common in insects.   They were observed by midieval monks who manually transcribed the bible and included the albino genetic "sports" as decorations in the margins of illuminated manuscripts.

Q38.2: I have personally seen American cockroaches ... that are not entirely brown. I have seen one (full grown adult) with partially white wings and my friend claimed to have collected one with white eyes. Are these rare finds?

A2: If injured while molting a cockroach may not fully tan its wings. White eyed Periplaneta cultures are available in some labs but I am not aware of how frequent the gene is in the wild and whether any of them are based on distinct genes. There are dozens of genes for abnormal colored eyes in Blattella germanica, not all are white. It would be interesting to cross the available white eye Periplaneta cultures to see if they complement each other (i.e. are from distinct mutant genes). These albino mutant eyes are mutations of the eye pigments which does not involve the cuticle and thus there are not the limitations to the structural properties of the cuticle as is with the surface integument.

Q38.3: I saw a documentary ... reputable organization who claims that a cockroach has two "brains" one in front and one behind. That is why a cockroach ... continues to function as per normal (except feeding) when its head is cut off. Is this true?

A3: That is true. The reproductive behavior is somewhat driven by its terminal abdominal ganglion, the VI abdominal ganglion, which is quite large. The preying mantid is in the same insect Order, Dictyoptera, and it is famous for the males prowess in completing sexual behavior after the female has bitten off the male's head. In this case the brain (in the head) is thought of inhibiting the reproductive behavior and when bitten off the reproductive behavior, released from inhibition and programmed into the VI ganglion, takes over.
The cockroach VI ganglion is responsible for coordinating the reknowned escape reflex of the cockroach. Delicate hairs on the cockroach hind end detect air rushing in front of a predator. The sensory hairs transmit their signals to the VI ganglion, it interprets the signals as an attack (or not) and accordingly sends a rapid message to the thoracic legs to start running. This escape reflex does not require the coordination by the (anterior) brain in the cockroach head.

Q37: Kunal Patel writes:  
(Does) the presence of an exoskeleton (in cockroaches) increase the efficiency of locomotion in comparison with the hydrostatic skeleton of worms?

A: Kunal,
I assume you are referring to annelid and polychaete worms and not the larvae of insects (e.g. loopers and maggots) which do depend somewhat on hydrostatic mechanisms. Given that spiders, like worms, have a partial hydrostatic skeleton I am not sure that there is any difference in efficiency unless you say that the success of insects vs spiders shows that the insect design is more successful. I would say that the variety of motion shown by insects is an indication of the benefits of the opposing-muscle approach to design. Insects have established several mechanisms of flight while spiders have only been able to do it by parachuting. Perhaps this is an indication of the limits of a hydrostatic skeleton. I am not sure that it says anything about the efficiency of comparable motion in a biophysical sense. When a hydraulic system is more efficient, the insect uses it. The spider is limited to using blood pressure to extend limbs, perhaps because they have not developed an easy local sclerotization of structures by which to create the fulcrum and levers for extensor muscles to work. Again this does not speak to whether the blood pressure extension is more or less efficient. I would think that controlling localized pressure differences allowing dexterious extension of one limb but retraction of another would seem to be less efficient. The tubular worms on the other hand do not in general have the problem of multiple appendages needing separate control; however they can extend different segments of their body by resisting extension in select regions by using their retractor muscles in those regions.

Q36: Samantha writes:  
I am doing a report on cockroaches and was wondering what are cockroach's support system(s)?

A: Samantha,
This is clearly an assignment from someone who knows the type of answer they want. I am not sure what the questioner wants.

I imagine that the majority of the approximate 3000 cockroach species are largely on their own in the environment.  Their support is based on their membership and place in the food web.  They are omnivores and thus eat almost any organic matter that does not fight back.  They are eaten by many small lizards, amphibians, mammals, and birds.  Domesticated cockroaches (about 10 species throughout the world) have found it easy to live with humans and get their food, water and shelter from the human shelters in which they live.  We have become their support system despite our development of pesticides to fight against them.

Q35: Diane Wilson writes:  
I am a graduate students at UAlbany (NY). Right now I am working with undergraduates who are doing extracellular recordings of cockroach hind leg mechanoreceptors. We are having a hard time keeping our roaches alive and have resorted to trying to catch them around the building with limited success. Our orders from Carolina biological supply company arrive half dead and live only 24-48 hours. I was hoping you have some suggestions as to a good source, trapping tactics and stratigies for maintenance.

A: Diane,
Cockroaches should be kept and reared at a temperature close to 30°C. If you allow them to chill they will die of cold shock. That is most likely the reason for your roach deaths after shipments made during the winter in your latitude. 25°C-30°C is the recommended growing temperature for Periplaneta. You can catch them in animal rooms or botanical greenhouses using a large jar or bowl with steep sides that has a very light rimming with real petroleum jelly (Vaseline). Bait the trap with banana or potatoes and carrots and place it in a warm moist area overnight. There is no excuse for failure!

Q34: M.I.A. writes:  
Also, how big is a cockroach baby or nymph? Occasionally I have seen very tiny (about the size of two fruit flys) beetle creatures in our apartment. (Are these baby cockroaches?)

A: M.I.A.,
I can not identify things I can not see. The size you mention is about the size of a first instar cockroach. You can see an example of a recently hatched first instar American cockroach on a dime at URL:
... a German cockroach newly hatched larva is half that size and black. Other beetle like creatures (such as carpet beetles and flower beetles) can invade a house also.

Q33: M.I.A. writes:  
Also, My roommate says that, if you have previously never seen any cockroaches in your room, but one day you see a huge one, then it is a scout, and is not really indicative of the size or amount of cockroaches which might be living within your walls. Is this true?

A: M.I.A.,
The large roaches are more likely to travel than a small roach. They do not have a social network that would include scouts. Bigger stride and wings allow adult cockroaches to travel further. Some male cockroaches can even gain altitude when they fly, most only use their wings to glide.

Q32: M.I.A. writes:  
My roommate believes that cockroaches don't like air conditioning. ... we live in Hawaii, and air conditioning makes the temperature around us liveable, plus it can cause droplets of water to form, .... What is your opinion?

A: M.I.A.,
Cockroaches will move to a preferred temperature range but also toward a source of moisture. They prefer a temperature between 25-30°C. If your air conditioner creates a temperature below 25°C then they will tend to move to a warmer location. 25°C is (25x9/5 +32) = 77°F so your air conditioner is probably set to cool below 77°F and tend to repel them. If you turn your AC off occasionally, the water the AC has dripped outside may have attracted cockroaches and provide a local source of cockroaches to move into your temporarily unconditioned space. It is not a simple question.

Q31: Pam Pollister writes:  
What color is the blood of a cockroach?

A: Pam,
The long answer:
Cockroach blood is not red because they do not use hemoglobin to carry oxygen. In fact their bloodstream is not used to carry oxygen either. They use a system of pipes called tracheae to bring the oxygen and remove carbon dioxide from their tissues.
As a result other factors determine the blood color. Male cockroaches have relatively colorless blood. Larval females have colorless blood. Only adult females which are producing eggs have a slightly orange blood because of the protein vitellogenin which is made in the cockroach liver (its fat body) and transported through the blood to the ovary. This protein like chicken yolk is orange because it carries a carotenoid, which is a vitamin A like molecule needed by embryos to develop normally.
The short answer:
Cockroach female adult blood is occasionally orange. All other cockroach blood is colorless.

Q30: Clifford writes:  
Are cockroaches really members of the Carp (fish) Family?

A: Clifford,
A cockroach and a carp are in two different Phyla. The cockroach is an Arthropod and the carp is a Vertebrate. The closest traditional link is that they are both in the Animal Kingdom. Some have been confused perhaps by the close spelling of the Stick Insect's scientific name, Carausius morosus, URL:
and the gold fish's scientific name, Carasius auratus, URL:
The similar spelling of the Genera of the stick insect (Carausius) which is sometimes grouped with the cockroach and the goldfish (Carasius) which is related to the carp could have confused some into thinking a carp and cockroach were closely related.  However your confusion is more likely based on the carp having another common name, the roach, BUT not the cock-roach.

Q29: Leigh writes:  
Me and my friends wanna know if the myth is true or its just an urban legend that cockroachs' eggs spread when u squish them with your shoe and you can spread them around where you walk?

A: Leigh,
You and you friends are possibly responding to the urban paranoia about contracting and spreading cockroaches in ones work and home environments. It seems that they are everywhere and if your apartment or home gets infested one can begin to speculate on how those buggers got into your 'space'. You have correctly identified it as an urban legend.
It is highly unlikely that a cockroach egg case (ootheca) would survive a classic smooth leather soled shoe. But who wears smooth soled shoes these days? If an ootheca was lucky enough to lodge itself into the honeycomb of a sport shoe tread and the person took off the shoe in disgust and threw it in the corner, I could imagine the eggs surviving and the brutal attempt to end their young lives might have failed.
However the ootheca and contained eggs are huge and mechanically fairly fragile. Any good mashing should kill them all.
I am sorry if I have started another urban legend about the paranoia of passing cockroaches with improper footgear!
I am not recommending going back to smooth soled shoes but I would recommend looking at the size of the waffle holes in your sport/walking/running shoes to see how they compare to the size of an ootheca which is about the size of a pea.

Q28: Lynn Gant writes:  
What do cockroaches eat?

A: Lynn,
Cockroaches are omnivores, like us. For the most part they will eat anything organic. Mostly they eat dead or immobile things. As indicated elesewhere in the FAQ, they rarely bite a human but might nibble on a sore in the middle of the night when an animal is sleeping.
They will eat the glue off the back of postage stamps and the glue bindings off the backs of books, traditional glue being derived from animal protein.

Q27: Bill writes:  
Do cockroaches live in cold climates. Or put it another way. "Can cockroaches live in Canada?" withstanding long cold winters? Please settle an argument! I have been told cockroaches can not live in Edmonton Alberta. Is this True? or False?

A: Bill,
Domestic pests certainly can live in houses in Canada but not outside, the way they do in Florida or the Gulf coast.
There are numerous wild cockroach species which can live in Canada as they do in the northern USA. The adults or larvae over-winter in the ground litter and effectively hibernate. There are some of these species that I have reared in the lab which queue up at a particular larval stage and refuse to proceed with their development toward the adult stage until you give them an artificial winter.

Q26: Felicity West writes:  
I would like to know why this is called a German cockroach please? There are apparently no cockroaches in Germany so where does the name originate from?

A: Felicity,
The chief biologist at the Munich TierPark (zoo) said they had no German cockroaches in their zoo and gave me three tropical species that they knew were living in various environments they maintained in the park. But I knew better. I went to the reptile house which is kept hot and humid and saw loads of Blattella germanica (Linnaeus,1767) in the space of a half hour, and during the day at that!   B. germanica, the German cockroach, probably entered Europe with Marco Polo or along early trade routes. Southeast Asia is its most likely origin. There are several sibling species that are very close to B. germanica; some even cross breed with it. Its relatives are common around pig stys in the outer islands of Hong Kong. Live pigs were often kept on exploration ships during long trips. It became associated with man and traveled around the world. It was formally named by Linnaeus and probably was around in Germany for quite a while before the name was applied. In Germany it is sometimes called "Die russische Schabe", The Russian Roach. In Russia it is called the Polish Roach. In America it was called the Crotton Bug because it came to NY about the time the Crotton Aqueduct was built which was pilloried in the papers because it took so much land by eminent domain.
The American Cockroach, Periplaneta americana (Linnaeus 1758) likewise is a misnomer since it probably originated in North Africa before becoming a world traveler. It most likely reached the Americas during the early slave trade.
There are thousands of species of cockroach and only about 10 have become cosmopolitan pests of man. Most of the others do not even have a common name.

Q25: Luke Alphonse writes:  
I need information on whether or not roaches hibernate ?

A: Luke,
The wild cockroaches in the northern USA do hibernate. They go into a suspended state of development in late fall and then they must go through a dormancy phase in the winter before they will resume development in the spring. If you keep them in a warm environment during the winter they will not develop any further and remain in a suspended state for more than a year. This phenomenon has not been published on as far as I know. The species I know this about through my unpublished research are Parcoblatta pensylvanicus and Parcoblatta virginica.   It would be interesting to know if these species go through this hibernation in the southern reaches of their range where a hard winter is not experienced.

Q24: Mkrs0042 writes:  
My daughter told me she was at a friends house and they had WHITE cockroaches!!! UGH. I have never heard of them. Is there a such creature?

A: Mkrs...,
That is a common observation; look at URL:

Q23: Nick writes:  
I am deathly afraid of cockroaches and it may soothe my fear a little if I knew they had a purpose.   What are cockroaches good for?

A: Nick,
Fear of domestic cockroach pests is perhaps warranted because they have been associated with the development of childhood asthma and thus it is better not to have them in your home environment.
Cockroaches as a group are part of the worldwide food web.   They are omnivore scavengers which clean up our environment and help recycle the organic litter that would accumulate if it were not decomposed by organisms which include cockroaches.   Furthermore they serve as food for small mammals, birds, amphibians and lizards.   There are over 3000 species of cockroaches and only 10 species are on the World Health Organization list of human pests.   The other 3000 species are welcome members of the biodiversity on this planet.

Q22: Joanna writes:  
Is the cockroach's brain spread around its body?

A: Joanna,
Insects as a group are said to think in their periphery.   This is because many of their innate behaviors are hardwired in peripheral ganglions more so than vertebrates.   For instance flying behavior is controlled in the thoracic ganglia and some reproductive behavior such as copulation is controlled in the last abdominal ganglion.   Whenever sexual behavior or flying behavior has to be coordinated with the visual system the behavior includes what you might call the brain (head ganglion).   The standard cockroach escape mechanism involves the tail (cerci) sensory signals that impinge on the terminal abdominal ganglion (A6) and giant fibers that communicate an escape signal from A6 to the 3 thoracic ganglia (T1-T3) which control the legs in running behavior.   So people might say that the cockroach's brain is spread around the body in abdominal ganglia A1-A6 and thoracic ganglia T1-T3 and head ganglia (brain, frontal and suboesophageal ganglion).

Q21: Ajay writes:  
Could You please let me know how do cockroaches breath?

A: Ajay,
Cockroaches, like all insects, breathe through a system of tubes called tracheae, a word similar to the name of the tube leading to our lungs. The tracheae of insects are attached to the spiracles which are small valved openings on the side of each body segment, excluding the head.  Thus the cockroach can breathe without its head!  The valves open when the CO2 level in the insect rises to an unacceptable level; then the CO2 diffuses out of the tracheae to the outside and fresh oxygen diffuses in. The tracheal system brings the air directly to cells because they branch continually like a tree until their finest divisions tracheoles are associated with each cell allowing gaseous oxygen to disolve in the cytoplasm lying across the fine cuticle lining of the tracheole. CO2 diffuses out of the cell into the tracheole.

Most insects do not have muscular lungs and thus do not actively breathe in the vertebrate lung manner. However in some very large insects the diffusion process may not be sufficient to provide oxygen at the necessary rate and body musculature may contract rhythmically to forceably move air out and in the spiracles and one can actually call this breathing. This might be associated with such activities as the energetic flight of the migratory locust.

Q20: Anthony writes:  
... a story (is) reputed to have aired on CNN about a woman, who while licking an envelope, got a paper cut from the flap on her tongue and was exposed to a cockroach egg which incubated inside her tongue. The woman later had the alive roach removed by a doctor. Is this possible?

A: Anthony,
This item is utter trash. The cockroach egg is huge. Most eggs are 2 mm long and are closely packed side by side and 2 by 2 like franks in a dozen package. They do not survive outside of the oothecae or egg case, which contains 12-40 of the eggs, and I can not imagine them being associated with the lickable surface of an envelope in any way such that they were transferred into a paper cut tongue. You just have to sit back and laugh at the gullible nature of the CNN producer/director who did not have enough biology in his education to know when he/she was out of her depth and needed to consult with someone who knew better. The producer/director of that program should be fired for promoting misinformation. I almost doubt that it ever aired.
Thanks for playing the skeptic!

Q19: Rachele Besley writes:  
I am a ... student from New Zealand doing a study on Cockroaches and was wondering whether you could tell me something on their response to light, whether they are attracted to it or not and whether it affects their behaviour.

A: Rachele,
I did a quick search on cockroach circadian behavior and found the following references ... of papers.
I understand that you ... may not be aware of some of the technical language in these (titles) but perhaps some of it will be useful. Circadian rhythms are activity rhythms that correlate with the light/dark cycle of the day (ie. the normal 24 hour day/night light rhythm). When organisms are put into constant dark they continue to behave as if the normal light/dark cycle was still there; that is they anticipate being awake when they normally would, during the 4 hours after lights go off at night. This internal clock can be reset by an artificially imposed lights off that a researcher imposes in a research arena. This demonstrates that the cockroaches respond to light and can reset their internal clock to a new rhythm as they should be able to since dusk changes its time of onset gradually during the year.
You can do a search of the scientific literature using other key words at the following URL:
For example try searching for the keywords: cockroach vision
This is one of the free ways of searching the scientific literature that you can do yourself. When you find things you do not understand you can try finding an expert to explain the issue, such as one of the authors in the paper with which you are having problems.
Good luck with your quest!
Papers on "cockroach AND circadian" found on MEDLINE 7/4/2000:
Bult, R. and H. A. Mastebroek (1993). “Circadian control of visual information processing in the optic lobe of the giant cockroach Blaberus giganteus.” J Biol Rhythms 8(4): 311-23
Colwell, C. S. and T. L. Page (1990). “A circadian rhythm in neural activity can be recorded from the central nervous system of the cockroach.” J Comp Physiol [A] 166(5): 643-9
Eesa, N., L. K. Cutkomp, et al. (1987). “Circadian change of dichlorvos lethality (LD 50) in the cockroach in LD 14:10 and continuous red light.” Prog Clin Biol Res: 265-79. 227a
Ferrell, B. R. and B. G. Reitcheck (1993). “Circadian changes in cockroach ommatidial structure.” J Comp Physiol [A] 173(5): 549-55
Lavialle, M., C. Chabanet, et al. (1989). “The 24-h rhythm of metabolic activity of the cockroach circadian pacemaker.” Neurosci Lett 105(1-2): 86-90
Lin, T. M. and H. J. Lee (1996). “The expression of locomotor circadian rhythm in female German cockroach, Blattella germanica (L.).” Chronobiol Int 13(2): 81-91
Page, T. L. (1981). “Effects of localized low-temperature pulses on the cockroach circadian pacemaker.” Am J Physiol 240(3): R144-50
Page, T. L. (1987). “Serotonin phase-shifts the circadian rhythm of locomotor activity in the cockroach.” J Biol Rhythms 2(1): 23-34
Page, T. L. (1990). “Circadian rhythms of locomotor activity in cockroach nymphs: free running and entrainment.” J Biol Rhythms 5(4): 273-89
Petri, B. and M. Stengl (1997). “Pigment-dispersing hormone shifts the phase of the circadian pacemaker of the cockroach Leucophaea maderae.” J Neurosci 17(11): 4087-93
Saunders, D. S. and E. J. Thomson (1977). “'Strong' phase response curve for the circadian rhythm of locomotor activity in a cockroach (Nauphoeta cinerea).” Nature 270(5634): 241-3
Sokolove, P. G. (1975). “Localization of the cockroach optic lobe circadian pacemaker with microlesions.” Brain Res 87(1): 13-21
Stengl, M. and U. Homberg (1994). “Pigment-dispersing hormone-immunoreactive neurons in the cockroach Leucophaea maderae share properties with circadian pacemaker neurons.” J Comp Physiol [A] 175(2): 203-13
Vijayalakshimi, S., P. M. Mohan, et al. (1977). “Circadian rhythmicity in the nervous system of the cockroach, Periplaneta americana.” J Insect Physiol 23(2): 195-202.
Wills, S. A., T. L. Page, et al. (1985). “Circadian rhythms in the electroretinogram of the cockroach.” J Biol Rhythms 1(1): 25-37.

Q18: Sean McGurn writes:  
could you please let me know if cockroaches fly. if so, have you heard of a species that flies in the palm springs area.

A: Sean,
If you are in Palm Springs FL you could be seeing _Blattella asahinae_ the recent import from SE Asia which is a very close relative to the German cockroach. The import can fly and interbreeds with _B. germanica_ which leads people to think that _B. asahinae_ was the wild species from which the non-flying domesticated species was derived.
Another flying cockroach is the Cuban Roach, Panchlora nivea, recently becoming common along the whole Gulf coast. It is bright mint green in color.
If you are in Palm Springs CA I do not have a clue as to what species you might be seeing. There are several wild cockroaches of the genus Parcoblatta in which the male flies. They are relatively inocuous and do not normally invade the home. They congregate at porch lights as do the species mentioned above.
A picture of the beast would help a lot.

Q17: Alex Stegemann writes:  
My father was drinking a Bud Light and on the last swig he discovered something in his mouth. After he spit it out we discovered it was (what we think is) a cockroach. About 6 minutes later, the cockroach began to move and tried to walk. We killed it! Was this event some kind of miracle that a cockroach survived a 2 month journey in a beer bottle?

A: Alex,
Sorry, My conclusion is that your father left his beer sit for a brief while and the roach decided to take a swig itself. No roach could have survived the bottling process.

Q16: Larry and Jennifer Jeffery write:  
I'm a Marine at Camp Lejuene down in North Carolina. I have heard many rumors about a very large roach being found at Camp Johnson which is part of Lejuene. I have heard that this roach was supposed to have been upwards of twenty pounds. I was wondering if you maybe knew anything about this? If it was at all possible I would like to get confirmation on this rumor and maybe a picture.

A: Larry and Jennifer,
Someone is pulling your leg. There is no roach even approaching a quarter of a pound. Perhaps they are refering to a lobster which is known as the cockroach of the sea since it is a scavenger:
Or, they may be refering to a freshwater fish, the carp, which is also known as a roach and could easily reach 20 pounds in weight. I do not have a picture of the fish.

Q15: Machelle Broschart writes:  
I am trying to write a paper on a type of roach that I found in my home. ... I ... cannot locate anything on flourecent green roaches. I was told that it is rare, but I would like more info ... I have the roach in a jar, thinking to preserve it due to its rare type. Please send more info ...

Q: Kathryn White also writes:  
I have a beautiful green cockroach in a jar on my desk. I have lived in Louisiana all my life and have never seen one like this. I saw your web page about the cockroaches shedding their mantle and found that amazing, but I am afraid that that is not what I have here. It has been in my jar for 2 days and there is no color change.

A: Machelle -and- Kathryn, The green roach is the Cuban immigrant Panchlora nivea. It is not rare on the mainland any more. It is found mainly in Florida to Texas along the Gulf coast. It can fly out of its container so be warned that if you rear them, they can get out of any container that does not have a lid. You can find out more info by searching the WWW for Panchlora.

Q14: Elaine and son write:  
We're trying to find out if common cockroaches (say American) verbalize or make sounds. ... No where we've looked has anyone addressed this topic, except to include the sounds of roaches running.

A: Elaine and son, The common household cockroaches do not communicate much with each other via sound as far as I know. Of course there are several thousand species and I am only familiar with about 35 species first hand.
There is one genus of cockroach Gromphadorhina which is known for hissing. This hissing is loud enough to scare a dog. The hissing cockroach is one of the types commonly reared by cockroach fanciers, URL:
Another species in the Oxyhaloinae which is commonly reared in labs, _Leucophaea maderae_, also makes a stridulating noise when handled. This is also most likely to scare whatever organism is trying to eat it rather than to warn its compatriots.

Q13: Lara Beatty of Calgary, Canada writes:  
A friend and I were discussing cockroaches the other day, and she claims that a cockroach can live for about 6 years without it's head. Is this a true fact?

A: Lara,
Not true, but your friend is correct that a cockroach could live a long time, perhaps a month, without its head. The only reason we need our head for basic survival is:
(1) We breath through our mouth or nose and the breathing rhythm is controlled in our brain. Cutting off our head would interphere with breathing although that could be maintained with a respirator.
(2) Cutting off our head could lead to blood loss and a drop in blood pressure which would result in death due to lack of blood transport of oxygen and nutrition to our tissues.
(3) Cutting off our head would prevent us from eating and we would die of starvation pretty quickly.
All of these reasons for dying are not present in cockroaches and many insects in general:
(1) Cockroaches breath through spiracles which are in each body segment and the blood does not carry oxygen to the tissues. The spiracles deliver air to each cell of the body through a set of tubes called tracheae. The brain does not control the breathing through the spiracles.
(2) The cockroach does not have blood pressure the way a mammal does and so cutting off the head does not lead to uncontrolled bleeding.
(3) The cockroach is a poikilotherm or cold blooded animal. They need much less food and a one day meal would be enough to last them a whole month as long as they were not extremely active. Without a head the cockroach would just sit around without doing anything much.
All this along with a cool temperature could allow the cockroach to last about a month without need for their head, as long as they did not get infected with a mold, bacterium or virus, which could kill them prematurely.

Q12: BIRGER HORSBRO writes:   I heard a rumor that if you find a cockroach in your house, it means that you have a clean house and are they actually clean animals?  

A: Birger,
The rumor, as many are, is 'right and wrong'.
Cockroaches clean themselves very scrupulously, as most insects do, in order that their sensory bristles on their body walls and limbs are ready to sense any hint of water, food, a mate or an enemy. Thirst, hunger, sex and safety rule the cockroach life.  A cockroach with a dirty exterior is not a 'lean mean machine'.
However, the cockroach GI tract can harbor all the diseases that are being passed around in the house or neighborhood. They are omnivorous and thus would just as likely eat a dead mouse or a bit of fallen cheese or nibble on your house plant. They often defecate near or on the food they eat so they are likely to pass the organisms in their GI tract to the food they are eating and the surfaces they walk and defecate on.
While they keep their bodies clean for their own protection, they are not and can not be 'house broken'. Think of them as an eternal puppy. The puppy will instinctually groom itself but, if it is not out in the wild woods, its feces will accumulate in its pen or in the home.  Of course cleaning up after the puppy is one strategy that works for a while.
You can keep a scrupulously clean home, but if there are cockroaches in the building they will seek out food and water and your apartment or kitchen/pantry may be the best place to find the small amounts of food they need to survive.  Seeing a single cockroach may be a sign that the population is low because there is only a very little waste food around to support a small roach population.
I hope this sets the rumor straight.

Q11: Terri Lamb asks: I was told that lobsters are the "roaches of the sea".   Therefore, I was under the impression that roaches are crustaceans.   Is this at all true? And if it is not true, what is the relationship between a roach and a lobster?

A: Terri,
As both a lobster and roach lover I can give you a reasonably authoritative answer.   If you go to the Tree of Life WWW page at the level Arthropod (Phylum), you will see that cockroaches are insects (Class Hexapoda) and lobsters are decapod crustaceans (Class Crustacea); they are two groups in the same phylum, URL:
Tree of Life (at Arthropoda level)
You can move up the tree to see how arthropods are related to other animals.
Beyond classification which should reflect the lobster and cockroach evolutionary relationship, the term 'roaches of the sea' reflects the behavior of lobsters as omnivorous scavengers.   Cockroaches will eat almost anything organic and so will lobsters.   They clean up the dead and dying plants and animals in their environment.
So much for the delicious taste of lobster?

Q10: I aquired a colony of B.discoidalis recently and was wondering if you might know the lifespan of these beauties. ... Bob

A: Bob,
You probably reached the right person because I did extensive culturing of Blaberus discoidalis many years ago and I can give you some good advice on their longevity.
Of course, my intention in those days was growing as many B. discoidalis as I could in as short a time as possible.   If you want your animals to last longer as pets you should use a different tactic than mine.
My whole approach to rearing cockroaches was to provide large numbers of animals of a uniform stage as well as age and therefore I also introduced the method of regulating food availability to keep the larval stages developing synchronously as I had published on for Blattella germanica at URL:
Using a similar approach I obtained the following information about B. discoidalis stadium length (i.e. length of each molting cycle).

40  +
    |                                   f  91%
    |                                   m 72%
    |                              f/m
    |                             9%/28%
30  + 
D   |
 A  |
  Y |                               o
20  +                   o   o   o
    |               o
    |           o
    |       o                                 ___KEY_to_SYMBOLS______
    |   o                                     o -larval molt
10  +                                         f -molt to adult female
    |___|___|___|___|___|___|___|___|___|__   m -molt to adult male
        1   2   3   4   5   6   7   8   9

If you can read this graph which represents the length of each stadium from time of first feeding until the actual ecdysis (sheding of the old cuticle), you can add up the days it would take to get from hatching to adult. Thus, as an example, 9% of females take 8 molting cycles to get to the adult stage and that represents 153 days. Such an adult female could live perhaps a year longer as an adult. All of this takes place at 30C the optimum temperature for growth and reproduction.   If you wanted to slow it down you could lower the temp to 25C and you would double all the times (approximately).

Q9: I am graduating in Assumption University (Thailand) . I am making a research about American cockroach life cycle. I would like to know more information about: (1.) how long the female cockroach takes to be pregnant; how long it can pregnant again after it produces the first egg case; and how many cases that can be produced per time; (2.) how many eggs in each case; (3.) how many times that the nymph can shed the skeleton; how long it takes for sheding at the first time; and how long it can shed again after the first sheding; (4.) what is the size and weight of nymph when its age is 6 months and 8 months; (5.) how old is the female cockroach can mate with the male at the first time.
Ms. Raevadee Nopsuwanchai

A: Raevadee,
You have asked a question a bit more detailed than the average. The information you ask for depends on details of the American cockroach, _Periplaneta americana_ life cycle which are not published in one place.   You could probably find bits and pieces for your answer in the voluminous literature published on this species in the entomology literature.  However, I did some reseach on this species in the early 1970's which I can share with you.  My intention was growing as many _P. americana_ as I could in as short a time as possible. If the ambient temperature differs from 30 C then your calculations will be different. My approach to rearing cockroaches was to provide large numbers of animals of a uniform stage as well as age and therefore I introduced the method of regulating food availability to keep the larval stages developing synchronously as I had published on for _Blattella germanica_ at URL:
Using a similar approach I obtained the following information about _P. americana_ stadium length (i.e. length of each molting cycle).

25  +
    |                                   m   m
    |                               m   f   f
    |                          (m/f=31%/20%)*   
    |                      (m/f=68%/70%)*
20  +                    (m/f=1%/4%)*
    |                                   n
    |                               f
    |                               n            
15  +                           n            
D   |                               o   o
 A  |
  Y |                           o                               
10  +                   o   o
    |           o   o   o  
    |   o   o   o                                 ___KEY_to_SYMBOLS______  
    |                                             o -larva to larva molt
    |                                             n -larva to nymph molt
 5  +___|___|___|___|___|___|___|___|___|___|     f -nymph to adult female molt
        1   2   3   4   5   6   7   8   9  10     m -nymph to adult male molt
                                                  * -percentage f or m to adult this molt.
                      Molt                        DAYS = days from feeding to ecdysis.

If you can read this graph which represents the length of each stadium from time of first feeding until the actual ecdysis (sheding of the old cuticle), you can add up the days it would take to get from hatching to adult. Thus, as an example, 70% of females take 9 molting cycles to get to the adult stage and that represents (8+8+8.5+9+9.5+10+12+16+23) = 104 days. Such an adult female could live perhaps a year longer as an adult. All of this takes place at 30 C, the optimum temperature for growth and reproduction. If you wanted to slow it down you could lower the temp to 25 C and you would double all the times (approximately). The adult female would take about 9 days to produce an ootheca containing about 12-16 eggs. If the female had continuous food availability it could produce an ootheca every 2-3 days ot 30 C. The newly hatched larva weighs about 2 mg and doubles its weight at each larva-larva molt. So after molt 1 the larva weighs 4 mg, after molt 2 ... 8 mg and so on.   Weight for a typical adult female is given in the Kunkel (1966) paper. You should refer to it for your research paper. Weight gain subsides at the larva-to-nymph and nymph-to-adult molts as more energy is put into transformation toward the adult form.

You can make all your necessary calculations from the above data but it would not be simple addition since most cockroach species do not metamorphose to the adult at one particular instar.

Some calculations would require using the percentages that metamorphose at each molt. Good luck!

Q8: What is the best, non-toxic way to kill cockroaches?  I have a five-year-old boy and a pet rat that get into everything.

A: I often tell people that I am not interested in killing cockroaches but rather learning about their life style and physiology.  I realize however that most people are more interested in killing them since they are pests in their houses and can contribute to spreading disease in hospitals and childhood asthma in the home.
Beware of most commercial preparations, even those that depend upon the 'natural' insect juvenile hormone.  Since these are relatively slow acting, the manufacturers often add a 'knock-down' additive poison which gratifies the user since it provides visual proof that the treatment works when it comes in direct contact with the pest.  Read the label of whatever poison you use.
I have come across several methods of killing cockroaches that are non-toxic to humans:
(1) Boric Acid.  The crystals of boric acid are sharp and get between the joints of an insect's exoskeleton. The sharp crystals abrade the cuticle and make the cockroach lose water and die of dehydration. This is a simple and cheap method. Dust the boric acid (which is relatively non-toxic) around the corners of rooms and in hiding places frequented by the roaches. A more expensive industrial version of this method is called Permadust. It is finely ground ruby dust which performs the same function as boric acid crystals but is more permanent. Boric acid washes away when you want to get rid of it.  You will find the dried carcasses of cockroaches in various hiding places as well as out in the open where they marched their last step searching for water.
(2) Live Traps.  Take a bowl or wide mouth bottle with steep sides; lightly Vaseline the inside wall up to the lip so that a cockroach can not climb up the slippery surface; place the bowl in a typical hiding place such as under your kitchen sink; place some food (bread, carrots, etc.) in the bowl as well as some toweling dampened with water; build some ramps up to the lip on the outside with paper toweling to encourage the cockroaches to easily enter the bowl.  This trap will quickly overnight accumulate a good sample of your household cockroach population.  Flush them down the toilet each morning for sanitary disposal.  Soon the cockroach population will be quite low and perhaps undetectable by you.
This later method would also provide your pet rat a non-toxic feeding station and your son a place to learn about the local fauna.  I would not be suprised if the pet rat ate some of the captives which are good sources of protein and vitamins.

Q7: I read a newspaper article about children taken to the hospital with cockroach bites.  Do cockroaches bite humans?

A: The cockroach is an omnivore, that is, it eats everything edible, animal and vegetable. So if we do not move around too much while sleeping they might be inclined to nibble on our earlobes at night. They are rarely aggressive enough to attack us while we are awake. When visiting Tulane University in New Orleans many years ago I slept in a dormitory room and cockroaches were flying down from the ceiling onto my head. I would guess that these large American cockroaches, _Periplaneta americana_, would be capable of taking a good bite out of me.  Only the larger species could take a bite through our skin. Of course the skin of children is much more tender and vulnerable to a roach bite.

Q6: Why do cockroaches die on their backs?

A:  First, few cockroaches die on their backs in the wild.  Natural death of cockroaches probably occurs in the stomach of a bird, bat or other small animal.
Second, Cockroaches are not used to living on a polished marble or vinyl floor.  They are more used to a ruguous living plane including leaves and sticks and other vegetable debris.  Thus when a cockroach finds itself on its back (by some mistake in its orienteering) it may have trouble righting itself if there is not debris around to grab hold of with its legs.  (Try it, put a cockroach on its back on a polished floor with and without some crinkled paper.)
Third, often we come across dead cockroaches in buildings that have died of insecticide.  Most of these insecticides are organophosphate nerve poisons.  The nerve poison often inhibits cholinesterase, an enzyme that breaks down acetyl choline (ACh), a neurotransmitter.  With extra ACh in the nervous system, the cockroach has muscular spasms which often result in the cockroach flipping on its back.  Without muscular coordination the cockroach cannot right itself and eventually dies in its upside down-position.

Q5:  Are cockroaches resistant to radiation?

A: I have been told that cockroaches are more resistant to radiation and in a world nuclear war, only the cockroaches would survive. But I have not seen any publication that discusses it with any credibility. I can give only an opinion of my own. I have irradiated cockroaches and constructed killing curves for them using gamma irradiation. I have not compared their resistance to radiation with any other organism using the same equipment and thus can not comment on any relative resistance based on hard data.
My opinion is that insects in general would be relatively resistant to radiation compared to non-insects, or non-arthropods more strictly. The lives of insects and other arthropods revolve around their molting cycles. During a molting cycle the cells of the insect divide usually only once. This is encoded in Dyar's Rule, i.e. insects double their weight at each molt and thus their cells need divide only once per molting cycle.
Now it just so happens that cells are most sensitive to radiation when they are dividing. That is the basis on which radiation is used to kill cancer cells. Cancer cells tend to divide more often than the other cells of our body. For a given dose of radiation you will kill more cancer cells than normal cells. With the right dose with the right cancer you can kill all the cancer cells while only killing some of the most rapidly dividing normal cells (i.e. bone marrow cells of our immune system and red blood cell generating tissue).
Now if a typical cockroach molts at most once a week, its cells usually divide within a 48 hour period within that week. That means that about 3/4 of the cockroaches would not have cells that are particularly radiation sensitive at any one time. If a killing radiation is endured by a cockroach and human population, then 3/4 of the cockroaches might survive while none of the humans might survive since our blood stem-cells and immune stem-cells are dividing all the time.
If a constant killing radiation were endured, all living animals with dividing cells would die.

Q4:  Do cockroaches sleep?

A: Yes, cockroaches do sleep, if you define it that way. Cockroaches have activity rhythms, i.e. regular times in the day when they are quiet and hide away from the rest of the world as well as wakeful times when they are active, seeking food, water and a mate. The subject of cockroach activity rhythms is well represented in the scientific literature (see my cockroach bibliography). In general, most pest species of cockroaches are active (i.e. awake) during the four hours after lights-out. That is why they are often visible when you go to the refrigerator for that midnight snack or come home late from the movies. They cue on that time when you normally shut off all the lights and go to bed. That ensuing four hours of activity is enough for them to get all their important business done without the high probability of running into you. I showed, in my first published paper, that one four hour stretch of food availability was enough to get them through an entire molting cycle of about 6 days. In a high density cockroach infestation the population may be forced to come out at other times to find food. If you have lowered the population down by using insecticides, whether that is a commercial insecticide or your boric acid application, the remaining few cockroaches will be satisfied with the four hour stretch after lights-out and you will rarely see them.
While we sleep they are active; while they sleep we are active.
How convenient!

Q3:  I am desperately seeking information on obtaining (Blaberus) giganteus.

A: I collected Blaberus giganteus in the garbage dump in Key West, Florida, 25 years ago.  I am told by my son that the garbage dump is no longer accessible.  Basically, in Florida or the Caribbean, you should look for some Palm trees with a lot of leaf litter below and look under the litter. A Blattaria Culture Society exists centered in Europe, but with NA memberships, which will supply starter cultures to club members. Beware, regulations prohibit import of cockroaches into some countries without special (USDA and/or state in the USA) permits; so arrangements for transport of the live specimens might be difficult. Finding a local enthusiast willing to share is your best bet.

Q2:  .... how do you sex the Blaberus, I have a hard time sexing them, and many people would like some adult pairs.

A:  Count the segments on the ventral surface of the male and female abdomen. The number of visible segments is higher in the male than the female. Also the females posterior abdomen is broader and more rounded than the male.

Q1:  I am sort of interested in why wildtype males have shorter wings than wildtype females... Could u tell me why???

A:  Wild type male cockroaches, in general, do not have shorter wings than females in proportion to their bodies.  In general cockroach females are more robust than males to allow for producing and carrying their large clutches of eggs.  Thus the females tend to be larger, for example in my illustration of Blaberus giganteus, AND THE FEMALE'S WINGS ARE THUS LARGER THAN THE MALE WINGS IN AN ABSOLUTE SENSE ONLY.  Some of this larger size is because females undergo more molts to get to the adult stage.  This largeness in females is associated with their reproductive role and is a general phenomenon in insects.  There is another phenomenon called brachyptery (short wingedness) which is associated with some cockroach species as a sexual dimorphism.  The females of some species have strongly reduced wings which are useless for the gliding type of flight that cockroaches do.   (Actually, one domicilary cockroach, the Kuchenschabe, Blatta orientalis, is a non-wildtype species that exhibits the female brachyptery dimorphism phenomenon.)  This phenomenon is also related to reproduction in my reading of the literature.  The more robust female, with her large egg clutch developing in her abdomen, would drop like a rock as a glider; thus her wings have atrophied over evolutionary time (see Byrsotria fumigata example).  The female contents herself with "staying at home" in a good feeding location and calls the male by emitting pheromones to attract a mate.  It is the more gracile males' function to be attracted to the female over long distances and use its wings to glide down to her from the height of some bush or tree.

Some of the myriad species of cockroaches that have been described:

(For enlargements and text on the above cockroaches go to the 1908-1910 papers of Shelford.)

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last updated by JGK 8/20/2016 © 2019.