Encarsia formosa is a species of wasp and a well known parasitoid of greenhouse whitefly, used commercially for biological pest control.
The tiny females (about 0.6 mm long) are black with a yellow abdomen and opalescent wings. There are considerably fewer males than females. They are slightly larger and are completely black in coloration.
Females deposit 50-100 eggs individually inside the bodies of third instar nymphs or pupae of the host species. The wasp larvae develop through four instars in about two weeks at optimum temperatures. Parasitized greenhouse whitefly pupae turn black in about 10 days, while parasitized sweet potato whiteflies turn amber brown. Both are easily distinguished from unparasitized host pupae. Wasp pupation occurs within the whitefly body. Adult wasps emerge about 10 days later.