The poet Ogden Nash once said, "God made the fly and forgot to tell us why."
Around 12% of the known species of insects in the world are flies. Some of those species are actually considered beneficial because they prey on pest insects. However, most of the flies that are found near human and animal habitats are simply nuisances, commonly called "filth flies".
Flies breed and lay eggs in garbage, animal feces and decaying organic materials. They land upon any kind of filth and carry it with them because of the sticky surface of their feet. Flies also regurgitate their stomach contents on any surface where they land.
Flies pose a threat to public health because they carry disease-causing organisms, viruses and bacteria. Flies are linked to the spread of more than 60 human and animal diseases including infectious hepatitis, conjunctivitis and salmonellosis. Fly management is an essential part of disease prevention among humans and animals.
Flies seek moist organic matter -- manure, garbage and compost -- in which to lay their eggs. An adult female housefly may lay up to 2,400 eggs in her lifetime. The eggs can hatch into larvae (maggots) in a single day. In hot weather, it can take only eight days for the eggs to complete the life cycle and become adult flies.
The primary food sources and breeding sites for flies are garbage and pet feces. More than a thousand flies a week can be produced within a single garbage can. Horse stables and dog kennels can also contribute to a fly problem. The warmer the weather, the faster the flies are produced. Fly problems usually worsen during or just after hot spells.
See how to identify some common filth flies.