As sometimes happens, early this week four insect specimens were dropped off at Capitol Pest for identification. These samples were presented in what I call “pests under glass” which is an insect taped to a piece of paper. Although this method of presentation is handy for the individual affecting the capture, collateral damage to the insect sample is usually considerable.
At first glance, these pests appeared to be the German cockroach Blattella germanica (L), but under the microscope these appeared to be Blattella vaga Hebard (Field Cockroach).These pests are very difficult to differentiate; features such as the size and shape of tergal glands and the genital hook of males, are generally seen as distinguishing features. Additionally, the use of morphological characters for species identification is further hampered when damaged specimens are used, as in the current situation.
Continue reading to learn more about identifying pests…
Using Pest Behavior for Identification
In situations such as this where samples are damaged, pest behavior is helpful in identifying the pest. Asian cockroaches are strong flyers and are attracted to light. A call to the individual who dropped off the sample confirmed the pests were not the German cockroach. No one in our organization had ever seen either Asian cockroach, Blattella vaga Hebard (Field cockroach) or B. asahinai: an Asian cockroach almost indistinguishable from the field cockroach.
The spread of Asian cockroaches into areas already infested with the German cockroaches creates identification and control problems for homeowners and pest control operators. This is further complicated by the presence of Asian and German cockroaches inside homes. Insecticide resistance in Asian cockroaches has not been reported, whereas German cockroaches often have resistance to various classes of insecticides. Compounding this problem for the homeowner is the ability of German and Asian cockroaches to interbreed and produce viable offspring. As this hybrid pest would be a combination of two hard to distinguish species, the identification and control of hybrids may be extremely difficult.