Average Size: They vary in size but are just slightly larger than an adult aphid: about 1/8 inch.
As the name implies, these wasps love aphids. They are all black and look similar to an ant with wings. The females lay their eggs inside the aphid and when they hatch, the young feed on the aphid eventually killing it. Almost (almost) makes you feel sorry for aphids. But not when they are chewing up your potatoes or brussels.
Active in the late summer and fall, aphidiid females can parasitize hundreds of aphids per day. You’ll know you have these wasps around if you see “aphid mummies” or paper-bag colored aphid shells stuck to leaves.