I have broken one of my "self-imposed rules" with this photo by using a picture that I didn't take! My friend, Diana, found this parasitized Tobacco caterpillar in her vegetable garden and sent me the picture to identify it. The white objects are the tiny coccoons of parasitic braconid wasps. Most of them are empty, according to the open ends. A few weeks ago the mother wasp laid her eggs on the caterpillar. When the larvae hatched they buried into the caterpillar and ate it alive. When they were ready to pupate, they exited the caterpillar's body and spun their coccoons. After pupation, they chewed a hole in the end of their cocoon and flew off to continue the cycle by laying their own eggs on a caterpillar!
Photo by Diana Stock-Prescott