Domestic flies, often called "Filth Flies," are not only a nuisance by their presence, but are important from a human and animal health standpoint. House flies may spread diseases such as conjunctivitis, poliomyelitis, typhoid fever, tuberculosis, anthrax, leprosy, cholera, diarrhea and dysentery. They may serve as intermediate hosts for parasitic tapeworms on poultry or parasitic roundworms on horses. Certain larvae of blow flies, bottle flies, screwworm flies and flesh flies may feed on dead as well as living tissue of mammals, causing blood poisoning and even death, especially in sheep. Stable flies bite painfully, sucking blood from humans and animals. False stable flies do not bite, but spread certain diseases, whereas the little house fly hovers in mid air in the middle of rooms.
Adults are about 1/6 to 1/4 inch long with reddish-brown eyes. Females are usually larger than males and have wider spacing between the eyes. They have two membranous wings; sponging or non-biting mouthparts; a dull gray body; and four narrow, black-lengthwise stripes on the thorax. Each female, during her three to four weeks of life, lays five to six batches of 75 to 100 small, white, oval eggs, largely in scattered garbage, that hatch in 12 to 24 hours into creamy white larvae. Larvae grow and pupate in four to seven days, and the last larval skin, which is hard and dark brown, is called a puparium. This stage lasts seven days, and can be the overwintering stage. The life cycle from egg to adult may be from 8 to 12 days in warm weather. A pair of flies beginning operation in April, if all were to live, would result in 191,010,000,000,000,000,000 (191 quintillion 10 quadrillion) flies by August. Allowing 1/8 cubic inch to a fly, this number would cover the earth 47 feet deep. Luckily, predators, parasites and other factors reduce fly populations. When feeding, house flies regurgitate some of their stomach contents on the food, which dissolves it. Then they suck it back into their stomach. They leave fecal deposits where they have walked. While walking and feeding on garbage, fecal material and food, flies may transfer disease organisms from both inside and outside their bodies. The flight range is from 2 to 20 miles.
Bottle and Blow Flies
Blow flies, sometimes known as green or blue bottle flies, are larger than common house flies. Some are characterized by metallic colors such as black (Phormia), blue (Calliphora) and green or copper (Phaenicia). Adults make a loud, droning buzz. Females lay eggs primarily on confined garbage. These flies are often attracted to dead animals, animal wounds, and feces-caked hair or wool on pets and farm animals. During warm autumn days, adults may gather on door and window screens and later enter homes for overwintering. Larvae are commonly found in garbage wastes and pet droppings. Larval development is completed in less than a week for green or copper blow flies and 10 to 20 days for black or blue blow flies. Larvae of screwworm flies may infest living flesh, especially at wound sites. Green bottle flies are seen on dog feces. The flight range is 3 to 10 miles.
Adults resemble overgrown house flies with three stripes on the thorax and a checkerboard pattern on their abdomen. Females deposit living maggots rather than eggs in decaying flesh of dead animals and excrement, especially dog stools. The life cycle is about eight days.
Black Garbage Fly
Adults are shiny black and about 2/3 the size of a house fly. Their life cycle is similar to the house fly. They may become abundant in piles of poultry and dairy cattle manure. The larvae are "beneficial" by preying on other fly larvae, especially the house fly. However, excessive numbers of adults may become annoying.
Drone Fly or Syrphid Fly
Adults are clothed in dense, short, yellow hairs giving the appearance of a large honey bee. Larvae, known as "Rattailed Maggots," develop in polluted water. The life cycle from egg to adult is about 30 days in the summer with the larval stages lasting about 18 days and the pupal stage about 10 days.
Adults resemble house flies except for the slender, pointed, sharp beak used to pierce skin and suck blood. Bites are painful. These flies may transmit anthrax and possibly infantile paralysis, leprosy, surra and swamp fever. Normally an outdoor fly, it attacks any warmblooded animal from rats to humans. Females lay four to five batches of eggs, each containing 100 to 150 eggs, in rotting straw; stable manure; moist, spilled feed; piles of lawn clippings; and piles of dead weeds washed along streams. The life cycle is about three weeks; both males and females suck blood.
False Stable Fly
Adults are similar to house flies, slightly larger and have a red mark on the back. They have sponging mouthparts, with females depositing eggs in animal manure, human excrement, tainted meals and decaying organic matter. Eggs develop into larvae that require 15 to 25 days to mature. Adults can transmit filth-related diseases.
Little House Fly
Adults are similar to house flies except they are smaller - 1/8 to 3/16 inch long. They have sponging mouthparts and feed on liquids. Male flies are usually seen in homes, where they hover in the middle of rooms. Females lay eggs in semiliquid organic matter such as animal and human excrement. The life cycle requires about 24 days.