Drosophila melanogaster
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Order: Diptera
Family: Drosophilidae
Subfamily: Drosophilinae

[Photo] Male Common Fruit Fly (Drosophila melanogaster). This image shows a 0.1 x 0.03 inch (2.5 x 0.8 mm) small Drosophila melanogaster fruitfly. Date 2005-07-16. Author: Andr?? Karwath aka Aka (http://commons.wikimedia.org/wiki/User:Aka).

Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order of the flies. The species is commonly known as the fruit fly, and is one of the most commonly used model organisms in biology, including studies in genetics, physiology and life history evolution. Flies belonging to the Tephritidae are also called fruit flies, which can lead to confusion.

Physical appearance
Wildtype fruit flies have red eyes, are yellow-brown in colour, and have transverse black rings across their abdomen. They exhibit sexual dimorphism: females are about 2.5 millimetres (0.1 inches) long; males are slightly smaller and the back of their bodies are darker. Males are easily distinguished from females based on colour differences (males have a distinct black patch at the abdomen, less noticeable in recently emerged flies (see fig)) and the sexcombs (a row of dark bristles on the tarsus of the first leg). Furthermore, males have a cluster of spiky hairs (claspers) surrounding the anus and genitals used to attach to the female during mating. There are extensive images at Fly Base.

Life cycle
The D. melanogaster lifespan is about 30 days at 29 °C (84 °F).

The developmental period for Drosophila melanogaster varies with temperature, as with many ectothermic species. The shortest development time (egg to adult), 7 days, is achieved at 28 °C (82 °F). Development times increase at higher temperatures (30 °C (86 °F), 11 days) due to heat stress. Under ideal conditions, the development time at 25 °C (77 °F) is 8.5 days, at 18 °C (64 °F) it takes 19 days and at 12 °C (54 °F) it takes over 50 days. Under crowded conditions, development time increases, while the emerging flies are smaller. Females lay some 400 eggs (embryos), about five at a time, into rotting fruit or other suitable material such as decaying mushrooms and sap fluxes. The eggs, which are about 0.5 millimetres long, hatch after 12???15 h (at 25 °C (77 °F)). The resulting larvae grow for about 4 days (at 25 °C) while molting twice (into 2nd- and 3rd-instar larvae), at about 24 and 48 h after eclosion. During this time, they feed on the microorganisms that decompose the fruit, as well as on the sugar of the fruit themselves. Then the larvae encapsulate in the puparium and undergo a four-day-long metamorphosis (at 25 °C), after which the adults eclose (emerge).

Females become receptive to courting males at about 8-12 hours after emergence. Males perform a sequence of five behavioral patterns to court females. First, males orient themselves while playing a courtship song by horizontally extending and vibrating their wings. Soon after, the male positions itself at the rear of the female's abdomen in a low posture to tap and lick the female genitalia. Finally, the male curls its abdomen, and attempts copulation. Females can reject males by moving away and extruding their ovipositor. The average duration of successful copulation is 30 minutes, during which males transfer a few hundred very long (1.76mm) sperm cells in seminal fluid to the female. Females store the sperm, which may need to compete with other males' stored sperm to fertilize eggs.

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