Encarsia formosa is a species of chalcidoid wasp and a well known parasitoid of greenhouse whitefly, one of the first to be used commercially for biological pest control, from the 1920s.

The tiny females (about 0.6 mm long) are black with a yellow abdomen and opalescent wings.

[2] Females deposit 50-100 eggs individually inside the bodies of nymphs or pupae of the host species.

E. formosa can use at least 15 species of whitefly as its host, including Bemisia tabaci and Aleyrodes proletella.

Use of the insect fell out of fashion due to the increased prevalence of chemical pesticides and was essentially non-existent by the 1940s.