Beneficial Insects

Parasitic Wasps

Parasitic Wasps
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This is a large group of insects with many different families. While some can be as long as 1 5/8 inches (the cicada killer), most parasitic wasps are tiny, black, and less than an eighth of an inch long, and as such, are frequently overlooked.

If you see an aphid that is swollen, puffed out, and tan in color, the chances are that it has been attacked by a parasitic wasp that has placed her egg inside the aphid. Once the egg hatches, the larva eats the aphid from the inside out, pupates, and cuts a circular exit hole from which the adult emerges. Other parasitic wasps lay multiple eggs in a caterpillar or other host. Many times, you’ll see a caterpillar such as a hornworm, with white, egg-like structures on its back. These are pupae of parasitic wasps that have completed development inside the severely weakened and soon-to-be-deceased caterpillar.

Value in the home landscape and garden: This is another important, under-appreciated, and poorly understood group. Parasitic wasps attack aphids, many types of caterpillars, cicadas, lace bugs, scale insects, whiteflies, sawfly larvae, ants, leafminers, and insect pupae. They also attack the eggs of insects such as codling moths, tomato hornworms, cabbage loopers, imported cabbageworms, and European corn borers.