Evil, thieving tomato hornworms (Manduca quinquemaculata) have invaded! Eating the tomatoes! Being all hornwormy! Fortunately, Cotesia wasps have followed the hornworms, using the fleshy veggie devourers as nesting grounds for their own rapacious larvae.
Cotesia are tiny wasps. They are host specific, so there is a particular wasp out looking for these tomato hornworms to inject full of eggs, along with a behavior altering virus. The eggs hatch, duh, they’re eggs, and the virus stops the hornworm from doing normal hornworm things, like moving or molting or turning into moths, making it easier for the wasps to munch the hornworm away as the larval wasps slowly devour the hornworm from the inside. Eventually the larva ooze out of the caterpillar, form cocoons, pupate, fly away, and look for more hornworms to infest or female wasps to breed with, depending on the gender of the wasp. Most useful little wasp. If you like tomatoes. Not if you like caterpillars, as the hornworms (and their moths) are quite attractive and make lovely embroideries.
Also, note that the critter nibbled (damn rabbits) vegetables are most excellent in gazpacho. Just use up your sad veggies, it’ll all be good.
“Cotesia congregata.” Encyclopedia of life, available from https://en.wikipedia.org/wiki/Cotesia_congregata. Accessed July 7, 2015.
“Tomato hornworm.” Encyclopedia of life, available from http://www.eol.org/pages/505248/overview. Accessed July 7, 2015.