When the eggs hatch, they begin to feed on the tomato hornworm internally. Once mature, the larvae chew their way out of the hornworm, spin a small cocoon and pupate. When the adult wasps emerge from their cocoons, the hornworm dies.
So if you see a tomato hornworm covered in small white cocoons, just leave it because it is hosting a new batch of parasitoids that can help rid your future garden of hornworms in about the most nature-friendly way we have. And I think most gardeners would call that a good thing.
Paper wasps are ones that most of us are probably familiar with, as they build those paper-like umbrella-shaped nests you have probably seen under the eaves of your homes or any number of other places. While they can sting if disturbed, they are mainly out there looking for food for themselves and their young. These wasps can be yellow, black, brown and red, depending on the species, and are usually ¾ to 1 inch in length. Their nests are constructed of chewed up wood and plants mixed with saliva.
New wasp colonies begin in the spring when a female leaves her hibernation site to build a nest. Most nests begin with a solitary female, but others join her to help build the nest and care for their young. The colony usually reaches its maximum size in late summer or early fall with 20 to 75 adults with nests that can vary from 3 inches to 10 inches in diameter. In the fall, the wasps seek mating partners. The males die off, and the females begin looking for a site to overwinter. The cycle begins again in the spring.