Vinegar flies, sometimes inaccurately called fruit flies, are small, slow-flying insects usually found in association with over-ripened fruit and vegetables. These insects are most abundant in the late summer months when vegetables or other fruit ripen and begin to ferment. Vinegar flies are common nuisance pests in restaurants, grocery stores, fruit markets, canneries, homes, and other locations that may attract these insects with fermenting or rotting vegetative matter.
Photo attribution link: By John Tann from Sydney, Australia (Drosophila immigrans side on) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
Vinegar fly adults vary (depending on species and food source) from 3 to 4 mm in length (25 mm = 1 inch), are light yellowish brown to dark brown in color, and may have darker markings on the dorsum of the thorax in the form of spots, blotches, or lines (Fig 1). Most have reddish eyes. The antennae have three segments with the third segment being oval and bearing a branched arista (hair-like structure), the branches of which are relatively long. The abdomen is typically darker than the thorax due to the presence of dark bands on the segments.
Female can lay up to 500 eggs which will develop to adult in about 7 days. Adult only lives for about 2 weeks.
Breeds in fermenting residues found in pubs, fruit & vegetables, breweries, etc. Larvae feed on bacteria and yeast found in rotting fruit and vegetable. May also breed in unclean drains and cleaning utensils.