Fruit Flies

Scientific Name: Drosophila spp.
CLASS/ORDER/FAMILY: Insecta/Diptera/Drosophilidae
METAMORPHOSIS: Complete

Introduction:

The common name of small fruit fly comes from their small size and fondness for fruits as egg laying and developmental sites. The name of vinegar fly comes from the fact they develop in the briny or vinegarlike liquids at the top of imperfectly sealed canned fruits and vegetables. Note that only flies of the family Tephritidae can properly be called fruit flies. These are nuisance pests but may act as disease vectors. The best known of these flies is D. melanogaster Meigen which has been used extensively in the study of heredity. They are worldwide in distribution and are found throughout the United States.

Recognition

(Drosophila spp.) Adults about 1/8" (3-4 mm) long, including the wings. Color dull, tan to brownish yellow or brownish black; eyes usually bright red. Antenna with feathery bristle (arista). Wing with coastal vein (thickened front margin) broken twice, near end of humeral cross vein (short vein perpendicular to costa near wing base) and near end of vein R1 (1st vein behind costa). First hind tarsal segment long and slender, much longer than 2nd segment. Drosophila melanogaster adults about 1/8" (3 mm) long, tan with abdomen blackish above and grayish below, and bright red eyes.

Similar Groups

(1) Small dung flies (Sphaeroceridae) with 1st hind tarsal segment broad and shorter than 2nd segment, wing with costar vein (thickened front margin) broken 3 times (additionally before humeral cross vein).

(2) Humpbacked flies (Phoridae) with humpback appearance, wing with strong/dark basal front veins (costar area) and 4-5 weaker (less distinct) unbranched oblique veins, hind femora flattened.

(3) Moth/drain/sewage flies (Psychodidae) have body and wing veins densely covered with hairs.

(4) Fungus gnats (Mycetophilidae) and darkwinged fungus gnats (Sciaridae) are slender, long-legged, mosquitolike, with elongated coxae, wing costa (front margin) unbroken, antenna lacks an arista/bristle.

(5) Other small flies either lack antenna with a feathery bristle and/or wing with a twice broken costar vein.

Biology

Adult females lay their eggs (average about 500) near the surface of fermenting fruits and vegetables or near the cover crack of imperfectly sealed containers of such materials. The eggs hatch in about 30 hours. The larvae develop in the briny or vinegarlike liquids of the fermenting materials where they feed near the surface and primarily on the yeast, for about 5-6 days. Prior to pupation, the larvae crawl to drier areas of the food or elsewhere. The brown, seedlike sheath containing the pupa (the puparium) is formed from the last larval skin/exoskeleton. The newly emerged adults mate in about 2 days. The life cycle (adult to adult) may be completed in 8-10 days at 85 degrees F (29 degrees C). Their reproductive potential is enormous.

There are over several known fruit fly species across the globe. Like other fly species, fruit flies experience a four-stage life cycle: beginning as eggs, they undergo larval and pupal stages before emerging as adults. The early life stages span approximately a few days and fruit flies can complete their development in as little as week in ideal temperature conditions. Adult fruit flies can live up to 30 days.

The common fruit fly (Drosophila melanogaster) is known for its ability to reproduce rapidly. The common fruit fly is a useful specimen in scientific research. The rapid life cycle allows researchers to study the effects of an experiment over a number of generations. Mutations are also common and easily followed in this fly species. Fruit flies have only four pairs of chromosomes: three autosomal pairs and one pair that determines sex. The entire compact genome of the common fruit fly was sequenced in 1998.

Habits

Small fruit flies are attracted primarily to fresh fruits and vegetables and those fermenting because of yeast. Materials lose their attractiveness when they begin to decay because of bacteria and fungi. Materials commonly infested include bananas, grapes, peaches, pineapples, tomatoes, mustard pickles, potatoes, etc. and fermenting liquids such as beer, cider, vinegar, and wine; some species are attracted to human and animal excrement. The larvae develop primarily in liquids and near the surface but seek drier areas for pupation.

Newly emerged adults are attracted to lights. Because of their short life cycle of 8-10 days, they can exploit many temporarily available developmental sites such as sour mop and broom heads, fruit under a table or cabinet, fruit left out in a bowl, etc. Dishwater and mop water full of food particles can accumulate on surfaces and/or in crevices and ferment, providing ideal fly breeding conditions.Adults tend to hover in small circles. Because of their small size, many species are able to penetrate ordinary screens.

Control

It is extremely difficult to rid a home of the common fruit fly. Fruit flies are attracted to sugary, organic materials. As their name suggests, they are commonly found infesting fruit. However, fruit flies are also capable of breeding in decaying meat, trash bins and large spills of soda or alcohol. Any fruit brought home following that should be stored in the refrigerator if appropriate. Regularly wipe counters, clean spills and empty your trash cans to help prevent fruit fly infestations.

The first step in addressing a fruit fly infestation is the destruction of their feeding and breeding grounds. Fruit flies often lay their eggs in rotten fruit and other soft, sweet, organic materials. If you identify a fruit fly infestation in your kitchen, dispose of all over-ripe or damaged fruit. Any subsequently purchased fruit or vegetables should be kept in the refrigerator until the fruit fly infestation dissipates.