Armored Scale Insects

Jeremy Andersen is a Masters Student, studying in Dr. Benjamin Normark's lab. Jeremy studies armored scale insects (Diaspididae), and is using phylogenetic techniques to understand the evolution of their genetic systems, as well as their associations with their plant hosts. Armored scale insects are a diverse lineage, with over 2400 species (Miller and Davidson 2005; Miller and Gimpel 2008), and are economically important. Adult females lack wings and legs and have reduced eyes and antennae. They are small insects (≤ 5mm) and usually cannot be identified without microscopic examination of a slide-mounted specimen. While armored scales may usually be identified to subfamily based on overall shape, either circular or elongate/oval, and a few other body characters may help identify specimens to genus; the main source of characters for identification is the pygidium (pictured above), which comprises abdominal segments 4-8. The pygidium includes the wax producing structures, vulva, and the anal opening. Armored scales have several adaptations that make them good invasive species. Due to their small size they are cryptic, and can easily be transported by humans on plant material (Rosen 1990). Interesting genetic adaptations also increase the rate at which armored scales can be spread. Many species reproduce via parthenogenesis, allowing a single female produce many offspring quickly, and without males. Also important to their ability to become invasive, is that their reproductive cycles are based on temperature and humidity. Members of the same species in two different habitats will produce different numbers of generations per year. In the north one generation is normal, while in the south as many as five is possible (Miller and Davidson 2005). Armored scales also display dimorphic forms depending on location on a plant. Members of the same species that are located on different parts of the plant, can produce different shapes, as well as different wax colors (Miller and Davidson 2005). The massive number of armored scales, and their difficult identification make them a perfect system to develop an accurate molecular identification system.