Encarsia formosa is a tiny parasitic wasp used to manage greenhouse whiteflies. The adult wasp lays an egg into the whitefly nymph. The E. formosa wasp larva that hatches from the egg feeds and pupates within the whitefly nymph, which then turn black usually within two weeks, depending on temperature. The adult wasp or parasite emerges by chewing a small circular exit hole in the tip of the blackened nymph. Adult female parasitoids also feed on young nymphs.
Encarsia formosa are shipped inside black, parasitized whitefly pupae, glued to small cards as seen in this photo. The round circle in the photo contains many small black parasitized pupae. A tiny adult wasp will emerge from each, then disperse in the greenhouse to search for whitefly nymphs to parasitize and feed on.