“Nature red in tooth and claw,” the poet Tennyson said.
Darwin thought these critters a clear disproof of creationism — no god would make such creatures intentionally!
Mark reports at The Divine Afflatus:
While admiring some ground cherries outside my front door, I noticed a number of leaves had been stripped off. Not grazed on by the deer that frequent the area, more like eaten by caterpillars. After a brief search I spotted a hornworm munching away. I didn’t bother killing the hornworm because, after all, the ground cherries are weeds growing amongst the black-eyed susans, and it’s less work for me if they take care of the weeds.
I looked again a few days later, and saw that the hornworm had sprouted numerous white appendages. These are the cocoons of pupating braconid wasps. Braconid wasps are parasitoids that inject their eggs beneath the skin of the host (hornworms are favored by the braconid wasp Contesia congregatus). After feeding on the convenient meal surrounding them, the wasp larvae emerge and spin their coccons, attached to the body of the unfortunate hornworm. In a few days, adult wasps emerge from their cocoons, leaving a dead caterpillar.
I later spotted a second hornworm, which suffered the same fate as the first.