In Illinois and Indiana, the western corn rootworm, Diabrotica virgifera virgifera, circumvents crop rotation as a control measure by ovipositing in soybean fields. Separation of behavioral phenotypes, between rotation-resistant and wild type females, is the first step in determining the genetic basis of rotation-resistance and in implementing new control measures. The time between release and departure from a bioassay arena was used as a measure of beetle activity to distinguish between types. Results from this assay indicate that D. v. virgifera females from regions where crop rotation is no longer effective are more active than females from regions where rotation does work. Effects of feeding and mating on behavior and a tendency to either walk or fly in the assay will also be discussed. Applicability of the assay as a quick method to distinguish types will be shown.