Gall Midge, any member of a family of small plant-feeding flies that cause swellings or distortions of plant tissue, called galls. They are also called gall gnats, gall flies, and cecidomyiids. Over 1200 species of gall midges are found in North America.
Adult gall midges are tiny flies that look like small mosquitoes. They are usually about 3 mm (0.13 in) long and have long slender antennae and one pair of mostly clear wings. Females of most species have a long, flexible egg-laying organ, called an ovipositor, for inserting eggs singly or in batches into narrow places, such as crevices in developing buds. Some species have a stiff ovipositor for puncturing tissue and they insert their eggs directly into plants.
The tiny eggs are colorless when laid but darken as they mature and become yellow, orange, or reddish before hatching. The larva is legless, flat to cylindrical, and tapered at both ends. It may be white, yellow, orange, or red, depending on the species and age. The larva uses its jawlike mouthparts to abrade or chew plant tissue. This feeding, and the insect's secretions, cause plant tissue to grow around the larva. This growth results in the formation of galls on leaves, flower heads, or stems.
Gall midges have complete metamorphosis. The larva develops through three growth stages, each separated by a molt of the skin. The larva then pupates within the gall or it exits the plant, dropping to the ground and digging into soil to pupate there. The oblong pupae commonly are colored like mature larvae or are somewhat darker. Both pupae and mature larvae of most species are 4 mm (0.18 in) long or less. Development time from egg to adult varies depending on the species and location. Some species have several generations each year, while others can take two or three years to complete one generation.
Each gall-forming species feeds inside only one or a few related species of plants. Larvae of a few species feed on fungi or decaying organic matter. Some are important predators of mites or small, soft-bodied insects. One such species, the aphid midge, is reared and sold commercially for release in greenhouses to control aphids.
Scientific classification: Gall midges are in the family Cecidomyiidae, order Diptera. The aphid midge is Aphidoletes aphidimyza.