Parasitic wasps

Pests eaten:
aphids, beetles, caterpillars, flies, gypsy moth, leafminers, moths, sawflies, scale insects, spiders, true bugs, weevil, wood-boring beetle larvae

Some favorite plants:
caraway, fennel, goldenrod, dill, coriander, Queen Anne's lace, fernleaf yarrow, golden chamomile, cosmos, marigold (lemon gem), tansy, cornflower, parsley

Description:
There are many kinds of parasitic wasps ranging in size from 1/100 of an inch to 3/4 of an inch. Most resemble wasps except they have no stinger. Many parasitic wasps lay their eggs inside of their host. The eggs then hatch, the larvae grow inside of the host and then chew their way out as adults.

YouTube videos:
Parasitic wasp vs. whitefly
Parasitic wasps & aphids

Resources:
AgriLife Extension, Texas A&M System
Cornell University's Biological Control: A Guide to Natural Enemies in North America