Here's a beautiful thing.
|A small hornworm with its burden of pupating wasps|
|A larger caterpillar climbs a squash stalk|
The parasitic brachonid wasp (cotesia congregatus) uses its long ovipositor to lay eggs inside the body of the tomato hornworm. When these hatch, they eat the innards of the hornworm before burrowing out and pupating in cocoons attached to the dying caterpillar.
All the gardeners say to leave such caterpillars be, since these wasps are the best ally you've got against the beasts.
I think people who use insecticides miss half the fun of gardening.