Flies are insects that belong to the order Diptera. The name of the order is Greek and means two wings, referring to the fact that flies have only one pair of wings and a pair of halteres. The halteres are small knobs derived from the hind wings that help the animal maintain the balance while flying. There are some species that have fly in their names but do not belong to the order of Diptera.
There are about 240,000 species in the order but only about half have been scientifically described. The order consists primarily of mosquitoes, gnats and midgets and is the area of insects most crucial to humans since they can transmit diseases. Mosquitoes, for instance, act as vectors for infectious diseases such as malaria, dengue or encephalitis.
The body of a fly is adapted to flying, therefore it is streamlined and short. A fly’s eyes are large and made up of compounds of individual eye units pointing into slightly different directions, thus giving the insect a very large view angle and permitting it to detect fast movement. Flies consume only liquids because they have no organ that enables them to eat solid food.
Flies mate effectively and quickly, producing a large offspring. The eggs are laid close to a food source, hatch immediately and develop rapidly into adults. The larvae can also hatch inside the mother. Fly pupae can take various forms, some even develop in a silk cocoon. Adult flies rarely live longer than a few days, mostly to reproduce and look for new sources of food.
Flies have been connected to death and the devil since their maggots feed on dead flesh. One of the seven princes of hell is called Beelzebub, or literally translated Lord of the Flies, who is identified as Satan in the New Testament. Despite their negative connotation however, maggots can be of great use to forensic scientists who can detect the time and place of death by the maggots’ development and size. Moreover, maggots are used by humans as bait for fishing and as food for pets like reptiles and birds, and are bred specifically for these purposes. They are also used in medicine for effective wound cleaning.