Fly is a two-winged insect that has some 90,000 different species of it. The housefly (musca domestica) is one of the most common of all flies. You must have seen flies rubbing their legs together. Do you know why they do so? The housefly has a dull gray, bristled body that is about 7 millimetres in length. It has large reddish compound eyes. Its mouth cannot bite but consists of a spongy pad. It has a peculiar system of feeding itself. At first, it releases saliva and digestive juices over food and then sponges up the resulting solution. In this way, flies contaminate large amounts of food with germs, and cause millions of deaths every year. Hence it is widely considered as a major health hazard. The whole body of the housefly, including claws and padded feet, is covered with bristles. Even its tongue is coated with a sticky glue. A fly rubs its legs together just to clean itself. In the process of rubbing the legs, it scraps some of the material that has gathered on the bristles and thus drops germs of dangerous diseases on the food. When we eat this food, we may get infected. Some of the most common diseases spread by the housefly are typhoid, tuberculosis and dysentery. Flies gather such germs from garbage and sewage. Houseflies usually live and breed in or near garbage or organic wastes. The female lays about 100 eggs at a time and as many as 1000 during her life. The eggs hatch into larvae in 12 - 30 hours. The larvae moult several times before becoming pupae. Within a few days, the pupae become adult and the cycle begins again. Most houseflies have a lifespan of about 30 days during summers and longer when the weather is cooler. Cold weather usually kills the adults; but larvae and pupae are able to survive the winter.