HOUSE FLY

Identification, Facts, & Control

Latin Name

Musca domestica

Appearance

1/3in long with four dark stripes on thorax

The common housefly (Musca dometica) is so named because it was one of the most common flies found in houses during the horse and buggy days when such a survey was made. It is still the most common fly found in houses across the United States throughout the year although other species may be dominant for short periods of time for various reasons.

The common housefly is about one—third inch long and can be identified by locating the four dark stripes that occur lengthwise (longitudinal) on the topside of the thorax. The fourth vein on the wings is also characteristically curved (angled) in shape rather than straight House flies lay their eggs in batches of seventy five to one hundred and fifty eggs per batch, directly upon the material that the larvae (known as maggots) will eat when they hatch. This material could be excrement, garbage and other decaying materials. Garbage and dog manure seem to be the main larval food source in residential neighborhoods although there can be a number of s other contributing sources. In restaurants and other food handling establishments, build ups of spilled food, grease unwashed trash dumpsters and garbage are the primary larval food sources. Eggs laid by house flies hatch into cream—colored larvae (maggots) in approximately twenty-four hours. The larvae burrow into the food material on which they have hatched and begin to feed and grow. The larva is the stage of the house fly life cycle that does most of the eating and all of the growing. As the larva develops, it casts its exoskeleton to pass from one instar stage to another. This process takes a minimum of three days and can take as long as three weeks. The hotter the weather, the faster the life cycle proceeds. The larva spends its entire time in the media in which it finds itself when hatching from the egg. The larvae are not readily visible to anyone looking at piles of infested garbage or manure because they tend to stay beneath the surface of the media. Thus, one needs to stir into the garbage or turn over the dog manure to see the presence of the larvae. It is amazing to realize how little 2 decaying organic material will play host to so many fly larvae. As previously stated, the female fly will deposit 75 to 150 eggs in a batch, but may lay several batches in one media source (or another adult female may also lay her eggs in the same media source). Thus, the one—time deposit of an Irish Setter may serve as "home" for more than one thousand fly larvae or a small size garbage pail may serve as home for thousands of fly larvae or a box full of decomposing grass clippings one cubic foot in size may serve as home for a thousand or more larvae.

House fly larvae are about one—half inch long and have a rounded, blunt end and a more pointed, opposite end. The head is located at the pointed end. House fly larvae breathe through spiracles located on their posterior (blunt) end. The sharp service technician can identify various species of larvae by the placement, size and shape of the spiracular plates.

As the larva becomes fully developed and ready to pass on to the pupa stage, it is beset with an urge to wander. This is called a migrating tendency and is really an attempt on the part of the larva to find a safe place to pass its pupal stage away from the media on which it has developed. It leaves the dog dropping or climbs up over the edge of the garbage can or out from under a layer of sludge under the restaurant refrigerator and seeks out a crack or crevice or some other "protection" such as a board or other object under which it can e crawl and be out of sight and fully safe as it passes its rather helpless pupal stage. This migrating tendency is a very strong one and is responsible for the fact that pupae can be found from several feet to several hundred yards from the original larval source.

The last larval "skin" (exoskeleton) becomes darker in color and forms the pupal case. As the pupa becomes older, the color of the pupal case proceeds from orange—red to darker reddish-brown to dark brown and in some cases, brownish—black. Inside of this pupal case, the maggot turns into an adult fly (metamorphosis = change). This process occurs in a minimum of three days and may normally take as long as three weeks or the fly may overwinter in this pupa stage. The pupa requires no food and is stationary. When the adult fly is fully is fully formed within the pupa case, it is ready to burst forth into the world. It escapes from the pupa case in an ingenious manner. Located near the top of the head of the adult fly is an "expander organ" which resembles a balloon. The fly inflates this balloon which acts like a pneumatic hammer to pop the top of the pupa case after which the fly painstakingly maneuvers its way out of the case. Thus, the life cycle of the fly is fully completed — egg, larva, pupa and adult.

Under warm conditions, the pupa stage may last only four to six days. In fact, during really hot weather when there is an optimum supply of food, the entire life cycle of the house fly may be completed in as little as eight days. Under more temper ate conditions, the house fly life cycle requires about three weeks. There may be as many as ten to twelve generations in one summer. Obviously, the statistics indicate the enormous breeding potential of house flies. In discussing the larval stage, it was mentioned that the larva was the primary eating- growing stage of the fly. When the fly hatches from the pupa, it therefore is as large as it is going to get. It does not grow at all once it has emerged from the pupa. However, the adult fly does take on nourishment in liquid form (in order to supply its energy requirements. House flies have lapping—sponging type mouthparts adapted for sucking up liquid foods. These mouthparts look like an elephant’s trunk with a big flat sponge on the end. The sponge like organ is mopped around in liquid food which is then taken up through the trunk—like part of the mouthparts. If a house fly lands on a desirable food that is in a dry condition (such as a sugar cube), it first "vomits" up onto the dry surface, dissolving some of the sugar in this liquid regurgitation and then, "sucks" the resulting sweet liquid up into the mouthparts. The process of first frequenting then eating off the surface of "food" such as human or animal excrement or garbage and then, regurgitating some of this material onto food inside homes shortly afterward is one of the ways in which flies transmit such diseases as dysentery and "summer diarrhea". Another obvious way in which flies can contaminate human food is when bits of filth adhere to their feet and body "hairs" and are deposited on food as they walk across food surfaces. Thus, the common house fly is a very undesirable creature to have around - either inside of the home, in restaurants, in food processing establishments or else where.

Houseflies are equipped with compound eyes with the eyes of the male being set significantly closer together (across the face of the fly) than the eyes of the female. Like other insects, house flies breathe through spiracles located on the mid-line of the thorax and abdomen. The thoracic spiracles of a house fly are surrounded by dense "hair" which sifts out foreign airborne particles.

Tests have been done to research the flight range of flies. Flies tagged with radioactive materials were released at a central point then collected in traps placed in concentric circles around the release point. Some species of flies trapped as far away as twenty five miles from the release point exhibited radioactivity. Research entomologists have found that house flies do not fly far from the areas where they breed. For example, one experiment was performed in which groups of marked house flies were rarely recovered farther than one mile away from the central release point. Thus, it is probably safe to say that most house flies do not move away from the larval source by more than one city block or two (if that far).

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