by Geraldine Warner, originally published 1993
The family Chamaemyiidae comprises a group of flies with larvae that are predators of soft-bodied insects, including aphids, mealybugs and scales. Within the largest genus, Leucopis, at least one species is known to attack the green apple aphid and grape mealybug in the Pacific Northwest.
Information on the life history of this predator is limited. Adults are small, grayish flies with pale stripes on their backs. The white, cylindrical eggs are laid in or near colonies of aphids and mealybugs. Larvae hatch in a few days and feed on nearby prey by breaking through the skin with their mouth hooks and sucking out the body contents. They are not very mobile and generally complete their development within a single aphid or mealybug colony.
Mature larvae are yellowish, almost cylindrical but gradually tapering toward the head end, and about 1/8 inch (3 mm) long. Larvae preying on mealybugs pupate within destroyed colonies, but those in aphid colonies usually drop to the ground to pupate. The life cycle from egg laying to adult takes about 30 to 40 days. Pupae formed late in the summer enter diapause and overwinter. There are probably 2 to 3 generations each year.