Aphid parasites: One parasitic wasp that attacks aphids (Aphidius testaceipes) is present throughout the country. It is responsible for creating the aphid "mummies" so commonly seen. The mummy is the brown shell of an aphid that has been killed by this tiny wasp parasite. The wasp larva develops in the aphid's body. After the larva pupates, it emerges as an adult wasp through a round hole it cuts in the mummy's back. This wasp reproduces throughout the warmer months of the year and effectively controls many aphid colonies.

Whitefly parasites: The whitefly parasite (Encarsia formosa) is a wasp that is particularly useful for control of whiteflies in greenhouses. The adult wasp lays eggs in whitefly pupae and larvae. As the immature wasp develops inside, the whitefly host turns black and dies. Several days later an adult wasp emerges. The entire life cycle takes as little as 20 days in warm weather. The whitefly parasite is only effective when temperatures average 75°F or warmer. In cooler temperatures the development of this parasite is delayed too much to effectively control the whitefly population.

Caterpillar parasites: Another common wasp parasite is Trichogramma. This minute wasp is so small it can lay its egg inside another insect egg. The adult is about 1/64 of an inch long. The host egg dies and turns black as the wasp larva develops. Trichogramma primarily attacks eggs of butterflies and moths. It is an important parasite of codling moth eggs. However, attempts to control codling moths by releasing large numbers of wasps have not been very successful. For maximum effectiveness, thousands of wasps must be released weekly during the time the pests are laying their eggs. The common wasp parasite of tomato and tobacco hornworms is Apanteles congregatus. This wasp lays eggs on the skin of the caterpillar. The wasp larvae hatch and burrow into the host. Many immature wasps feed and develop within the body of the caterpillar. They then move to the surface of the host and form small white cocoons that protrude from the back of the insect. Adult wasps emerge from the cocoons. The hornworm usually dies before the adult parasites emerge.