fruit fly, common name for any of the flies of the families Tephritidae and Drosophilidae. All fruit flies are very small insects that lay their eggs in various plant tissues. The Tephritidae contains about 1,200 species characterized by wide heads, black or steely green or blue bodies, iridescent greenish eyes, and wings that are usually mottled brown or black. The eggs of most species are laid directly in the pulp of the fruit on which the larvae feed; in North America, blueberries, cherries, and apples are much damaged by these insects. In warm regions, the Mediterranean fruit fly, Ceratitis capitata, was a serious pest of citrus fruits; it has now been eradicated from the S United States. Some species, e.g., the goldenrod gall fly, Eurosta solidaginis, which deposits its eggs in species of goldenrod, lay their eggs in plants of no economic importance. The Drosophilidae, or pomace flies, are yellowish and in the wild are largely found around decaying vegetation. The larvae living in fruit actually feed on the yeasts growing in the fruit. Drosophila melanogaster, also called vinegar fly, is a much used laboratory insect; its 10-day life cycle and large chromosomes, particularly those of the salivary glands of the larva, have made it invaluable in the study of genetics. Fruit flies are classified in the phylum Arthropoda, class Insecta, order Diptera, families Tephritidae and Drosophilidae.