Those Dirty Filth
Flies
The filth flies include the house fly, blowflies, flesh flies and their relatives. There are about 200 species of them. These flies have two membranous wings, lapping-sponging mouth parts, and lots of bristles all over their bodies. Their larvae live in various kinds of moist or decaying organic matter or dung. They feed by "spitting out" saliva and former stomach contents onto their intended next meal. After a few seconds, they suck up the fluid they spit out before, along with anything it might have dissolved. They are very mobile, moving hundreds of feet in a few seconds, and feed on nearly any substance. These flies can multiply rapidly. One female house fly can lay 75-150 eggs per batch, and a total of 350-900 eggs in her (average) lifetime. Adults usually live 15-25 days. Our problems arise when a fly feeds on some filth (for example, dung, or garbage) then a few seconds later lands on our plate or sandwich and tries to feed on the same morsel we intend to eat. Both the habit of regurgitating some of their stomach contents when they feed, and their very bristly ("hairy") bodies make it very easy for filth flies to transmit pathogens to humans. Filth flies have been proven to spread more than 65 kinds of human pathogens, including: typhoid, E. coli, cholera, polio, TB, "Staph", "Strep", leprosy, and several kinds of food poisoning. Control involves several steps. First, since there are so many species, you must collect a sample and get them accurately identified. Next, you have to do a survey to find out where the pest population is breeding. Control of the larvae is absolutely essential to controlling any population of filth flies. Sanitation is the next step. It includes cleaning up and removal of all of the material in which the flies are breeding (i.e., where you find their larvae). Depending on the species of pest involved, the breeding (larval) medium could be live earthworms, dung, a cadaver, rotting plant matter, or garbage. Your next step, mechanical control, may include closing cracks, replacing or repairing screens, using light traps, baited traps, air curtains over outside doors, and "sticky" ribbons or papers. Although there are a number of natural predators, parasites, and pathogens which attack house flies (for example), none of them is very successful in reducing fly populations under natural conditions.
After all these other steps have not accomplished the desired control, or (more often) when an immediate reduction of flies is required, properly labeled chemical pesticides may have to be used. These could be applied to flies’ resting surfaces, breeding sites which cannot be eliminated or adequately closed off, or in baits for adult flies, placed between breeding site(s) and location(s) you are trying to protect. Ultra-sonic devices have no effect, and IGRs are often of limited practical use. Sanitation and mechanical controls have the greatest long-term effect on reduction of filth fly populations.