True flies are insects of the Order Diptera (Greek: di = two, and pteron = wing), possessing a single pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax. The common housefly is a true fly and is one of the most widely distributed of animals.
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 Â°C (82 Â°F). Development times increase at higher temperatures (30 Â°C (86 Â°F), 11 days) due to heat stress. Under ideal conditions, the development time at 25 Â°C (77 Â°F) is 8.5 days, at 18 Â°C (64 Â°F) it takes 19 days and at 12 Â°C (54 Â°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 millimeters long, hatch after 12â€“15 h (at 25 Â°C (77 Â°F)).The resulting larvae grow for about 4 days (at 25 Â°C) while molting twice (into 2nd- and 3rd-instar larvae), at about 24 and 48 h after exclusion. 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 Â°C), after which the adults enclose (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.
Danger from flies
Several species of flies have adapted to live in human structures. When flies are found in human structures, they are always considered to be nuisance pests. Some kinds of flies are also a potential threat to human or animal health. These flies may act as carriers of disease organisms present in their breeding and egg-laying sites. These disease organisms can cause food poisoning, diarrhea, dysentery or typhoid fever