Is it difficult to distinguish between male and female corn rootworm beetles and gravid and nongravid females?
Distinguishing between male and female beetles is not difficult, particularly for western corn rootworms. Western corn rootworm males emerge first, followed by northern corn rootworm males, western corn rootworm females, and finally northern corn rootworm females. Northern corn rootworms, both male and female, are about 1/4-inch long and are uniformly green with no distinguishing stripes. The wing covers of male western corn rootworm beetles are mostly black, with a small tinge of yellow at the tips. Adult female western corn rootworms have three widely separated black stripes on yellow wing covers. Gravid females of both species ususally have swollen abdomens filled with eggs. If you squeeze a female rootworm’s abdomen and clear fluid is expressed, she probably is not gravid. If the fluid expressed looks and feels like tapioca, you probably have found a gravid female.
