Insect of the week (October 7, 2024) is Cotesia congregata. These are the wasp parasites that Na’im brought along with the caterpillar to our entomology pot luck on September 28. This wasp species is a member of the Hymenopteran family Bracondiae. It was originally described by Thomas Say in 1836. I created this photo from a series of 118 stacked images of a specimen in my collection. The large black item in the background is a standard sized #3 insect pin (yes, these are small animals).

Adult females lay their eggs in either the caterpillars of the tobacco or tomato hornworm. In addition to the eggs, the female injects symbiotic viruses and venom into the caterpillar. The viruses quiet the internal defense mechanisms of the caterpillar. Once the eggs hatch, they release special cells (called teratocytes) which work together with the venom and viruses to slow and stop the development of the caterpillar. The wasp larvae undergo 2 molts inside the caterpillar; the third instar larvae emerge and spin cocoons on the surface of the doomed caterpillar. Time from egg deposition to emergence of adult wasps is roughly 3 weeks.

Fun fact – This wasp has the shortest flagellated spermatozoa in the animal kingdom (6.6 microns long). 

Another fun fact – These wasps may also be parasitized by another species of wasp (a hyper-parasite) in the genus Hypopteromalus.

To learn more about this central Illinois wasp, visit this article on Wikipedia – https://en.wikipedia.org/wiki/Cotesia_congregata