Mystery photo #3 revealed

The last mystery photo was a close up of a caterpillar covered in parasitoid wasp cocoons! Here's the full size photo.

This is one caterpillar that won't ever be a butterfly (or moth). Why not? And what is a parasitoid wasp? The adult female wasps search for particular species of caterpillars and deposit the eggs inside the caterpillars' body. Then the wasp live inside the caterpillar and slowly eat it from the inside out. When the little buggers are finished, they make cocoons on the caterpillars' back and pupate. Then the next generation of wasps will emerge from the cocoons on the back! The caterpillar will die before it is able to pupate, and so it will never reach adulthood or reproduce.

Some insects like parasitoid wasps can be very beneficial for farmers if they lay eggs on caterpillar species that damage crops. You don't have to go to Africa to see parasitoid wasps! You can find them if you grow tomatoes in Chicago! Large, green caterpillars called tomato hornworms eat tomato plants, but also have their own parasitoid wasp species. The cocoons are very similar to these and will appear on the parasitized caterpillars (from a distance they look like they would be white oblong eggs, but if you look closely you can see the little threads of the cocoon).

One of the reasons I love studying biology is because I get to learn about fascinating relationships between different organisms. Would you ever have guessed that some wasps grow up inside a caterpillar!?