Flies are the only major group of insects that have only one pair of wings. The rear wings are reduced to small knoblike structures known as halteres, which help the insect control its flight. Reproduction Flies go through a complete metamorphosis of egg, larva, pupa, and adult. The eggs are usually laid in a medium that ensures the larvae adequate food, such as decaying animal flesh, dung, pond water, or fruit. Some flies are harmful to human beings, destroying crops and carrying such diseases as typhoid fever, anthrax, cholera, and dysentery.
Mosquitoes carry malaria, dengue fever, encephalitis, and elephantiasis.
Most species, however, are harmless to humans and play an important role in nature, pollinating plants and speeding the decomposition of animal carcasses, manure, and vegetable matter. Flies also consume many other insects, and they are an important food source for animals such as frogs , toads, lizards, and birds. It is impossible to drown a fly. A housefly beats its wings about 20,000 times per minute. Using various techniques, a state of consciousness is induced which allows total identification with a certain animal.