Aphid Midge / Home and Landscape / UC Statewide IPM Program (UC IPM)

Hosts or Prey

Aphids on foliage and succulent shoots

Identification

Adults are delicate flies with long slender antennae and legs. At rest the wings are commonly held above the body, angled and separated, and antennae are curled backwards over the body. The body is dark reddish brown or orange to yellowish brown. The wings are translucent with numerous, microscopic hairs. The body (excluding antennae) and wings are each 1/12 to 1/8 inch (2–3 mm) long.

Eggs are orange or reddish, oval, and about 1/100 inch (0.3 mm) long. They occur on aphid-infested foliage in scattered groups of about one-half dozen.

Larvae are orange, red, or yellowish maggots 1/8 inch (3 mm) or less in length. The round body tapers toward the head. Larvae commonly feed with their mouthparts attached to an aphid's leg joint from which they suck body contents. Midge feeding causes the aphid to become paralyzed, then shrivel into an empty skin.

Pupae occur in a roundish, silken cocoon in litter or topsoil. On the ground, plant bits and particles adhere to and obscure the silk. Less commonly pupation is on foliage, where shriveled skins of dead aphids may cover the cocoons.

Lookalikes

Aphidoletes thompsoni may occur in northern California due to movement from Oregon where it was introduced and established in the 1950s. The appearance of Aphidoletes aphidimyza and A. thompsoni can be distinguished only by an expert examination of microscopic characters. Because A. thompsoni is a specialized predator of adelgids, which occur only on foliage and shoots of conifers, the species generally can be discriminated by the type of prey and plant where they occur.

Aphidoletes adults resemble those of fungus gnats, Bradysia species, but can be distinguished by wing venation. Bradysia species. have a distinct, forked (Y-shaped) vein near the apex (tip) of each wing. Predaceous midges have a faint, forked vein in the posterior (outer) portion of wings. Both species can occur together, such as when plants are grown in containers or greenhouses where aphids and the root-feeding larvae of fungus gnats are common pests.

Life Cycle

Aphid midges develop through 4 life stages: egg, larva, pupa, and adult. After hatching, larvae develop through 3, increasingly larger instars. Each larva consumes about 3 to 50 aphids per day for about 1 week before pupating. Mature larvae commonly drop from plants to pupate on the ground or potting soil. Overwintering outdoors is as mature larvae (prepupae) in cocoons. After adults emerge and mate, each female lays about 70 tiny eggs during her lifespan of 1 to 2 weeks.

Egg to adult development time is about 3 weeks when temperatures average 72°F. In the field Aphidoletes has up to 6 generations per year, varying by day length and temperature. Aphid midges stop reproducing when day length is less than about 16 hours.

Habitat

The aphid midge in California occurs mostly in coastal locations and greenhouses and on low-growing plants that are frequently irrigated overhead. Aphid midges can be common on apple, pear, garden and vegetable crops, and ornamental bushes.

Dozens of aphid species are recorded prey of Aphidoletes larvae. For some aphids the aphid midge can provide important biological control. Adults are active during dusk to dawn and consume only liquids, especially honeydew. Without honeydew, females lay relatively few eggs.

Commercial Availability

Aphidoletes aphidimyza is commercially available and released for biological control of aphids in commercial greenhouses. When purchased, they generally are delivered as pupae in packing material such as sand or vermiculite.

To increase the effectiveness of resident natural enemies and any that are released

Avoid the use of broad-spectrum and persistent insecticides and miticides (acaricides).
Control ants and dust.
Grow flowering plants that provide nectar and pollen for adults (insectary plants).

See Natural Enemy Releases for Biological Control of Crop Pests, Protecting Natural Enemies and Pollinators, and Vendors of Beneficial Organisms in North America for more information.

Species

The cecidomyiid tribe Lestodiplosini is comprised entirely of natural enemies. Four species of Aphidoletes are known worldwide, and in California include A. aphidimyza and perhaps A. thompsoni. Prey of other Cecidomyiidae varies by the species and includes gall-making Cecidomyiidae, phylloxera, psyllids, scales, thrips, and whiteflies. Certain Cecidomyiidae are parasites (parasitoids), such as of aphids or psyllids. Mite midges, Feltiella species, feed on the adults, eggs, and immatures of spider mites.

The Cecidomyiidae family is commonly named gall midges because many species of Cecidomyiidae as larvae feed inside plant tissue, distorting foliage and shoots. The family includes the honeylocust pod gall midge, Monterey pine midge, and rose midge.