These in turn are divided into about 100 families. Flies can be found in most places in the world, and the common house fly Musca domestica has followed mankind to every corner of the earth. Flies have a holometabolous life cycle meaning that the egg hatches into a small grub like creature which don't look anything like a fly at all. The larvae eats and grows and occasionally sheds its skin until it is big enough to make an adult fly, then it pupates.
Flies are great opportunists and as adults they also eat a great variety of foods.
The mouth parts of adult flies are all designed either for sucking and sponging, or piercing and sucking. No adult fly can chew its food. Biting flies actually should be called stabbing flies. Flies have been of incredible importance to mankind all over the world, and it is possible to say that on many occasions it has been a fly which has changed history. This is because many of the primary diseases of man are transmitted by flies.