Small fruit fly and vinegar fly adults are about 1/8 in (3-4 mm) long, including wings.
True fruit flies are in a different group from these Drosophila species. Adult small fruit flies have antenna with a feathery bristle; wings with thickened front margins, intersected in two places. Mature Drosophila melanogaster larvae are about 1/4-3/8 in (7-8 mm) long, eyeless, legless, and tapered from large rounded rear to the pair of dark mouth hooks at the “head” end.
Adult Drosophila are dull tan to brownish yellow or brownish black; eyes usually bright red. Larvae are nearly white, except mouth hooks which are black, and the tips of the abdominal breathing pores which are yellowish.
Comparison with other species
True fruit flies are in the family Tephritidae, a different group. Small dung flies have wings with thickened front margins broken in three places. Humpbacked flies have humpback appearance. Moth/drain/sewage flies have body and wing veins covered densely with hairs. Fungus gnats and darkwinged fungus gnats are more mosquito-like, long legged, slender, antenna without the bristle.
Food! Small fruit flies develop on fruit. Vinegar flies develop in briny or vinegar-like liquids at the top of poorly sealed canned fruits and vegetables.
Fresh fruits and vegetables, such as bananas, grapes, peaches, pineapples, tomatoes; fermenting liquids, such as beer, cider, vinegar, and wine. When fresh materials decay they are less attractive to these flies, due to bacteria and fungi.
Drosophila females lay eggs near the surface of fermenting fruits and vegetables or in poorly sealed jars of these foods. Eggs take about 30 hours to hatch. Larvae develop in brine or vinegar of fermenting material. They feed near the surface, mostly on the yeast, for 5-6 days. They go to drier places to pupate. Newly emerged adults mate in about 2 days. The life cycle may be completed within 8-10 days at 85 degrees F (29 degrees C).
Small fruit flies and vinegar flies are nuisance pests which also transmit disease. Its short life cycle has made the species, Drosophila melanogaster, especially useful in the laboratory for biological research.
Vinegar flies and small fruit flies are small enough to go through ordinary screens.