The housefly, Musca domestica, is a fly of the suborder Cyclorrhapha. It is believed to have evolved in the Cenozoic era, possibly in the Middle East, and has spread all over the world. It is the most common fly species found in habitations. Adult insects are grey to black with four dark longitudinal lines on the thorax, slightly hairy bodies and a single pair of membranous wings. They have red eyes, and the slightly larger female has these set further apart than the male.
The female housefly usually mates only once and stores the sperm for later use. She lays batches of about 100 eggs on decaying organic matter such as garbage, carrion or feces. These soon hatch into legless white maggots which after 2 to 5 days of development transform into reddish-brown pupae, about 8 mm (0.3 in) long. Adult flies normally live for 2 to 4 weeks but can hibernate during the winter. The adults feed on a variety of liquid or semi-liquid substances beside solid materials which have been softened by saliva. They carry pathogens on their bodies and in their feces, and can contaminate food and contribute to the transfer of food-borne illnesses. For these reasons they are considered pests.
Houseflies have been used in the laboratory in research into ageing and sex determination. Flies appear in literature from Ancient Greek mythology and Aesop's The Impertinent Insect onwards. Authors sometimes choose the fly to speak of the brevity of life, as in William Blake's 1794 poem The Fly, which deals with mortality subject to uncontrollable circumstances.
Video Housefly
Description
Adult houseflies are usually 6 to 7 millimetres (0.24 to 0.28 inches) long with a wingspan of 13 to 15 millimetres (0.5 to 0.6 inches). The females are slightly larger than the males. The head is strongly convex in front and flat and slightly conical behind. The pair of large compound eyes almost touch in the male but are widely separated in the female. There are three simple eyes (ocelli) and a pair of short antennae. The mouthparts are specially adapted for a liquid diet; the mandibles and maxillae are reduced and non-functional and the other mouthparts form a retractable, flexible proboscis with an enlarged fleshy tip, the lamellum. This is a sponge-like structure that is characterised by many grooves, called pseudotracheae, which suck up fluids by capillary action. It is also used to distribute saliva to soften solid foods or collect loose particles.
The thorax is some shade of gray or sometimes even black, with four dark longitudinal lines of even width on the dorsal surface. The whole body is covered with short hairs. Like other Diptera, houseflies have only one pair of wings; what would be the hind pair is reduced to small halteres that aid in flight stability. The wings are translucent with a yellowish tinge at their base. Characteristically, the media vein (M1+2 or fourth long vein) shows a sharp upward bend. The abdomen is gray or yellowish with a dark stripe and irregular dark markings at the side. It has ten segments which bear spiracles for respiration. In males, the ninth segment bears a pair of claspers for copulation, and the tenth bears anal cerci in both sexes.
Species that appear similar to the housefly include:
- The lesser house fly, Fannia canicularis, is smaller, more slender, and the media vein is straight.
- The stable fly, Stomoxys calcitrans, has piercing mouthparts and the media vein is only slightly curved.
Maps Housefly
Life cycle
Each female fly can lay up to 500 eggs in a lifetime, in several batches of about 75 to 150. The eggs are white and are about 1.2 mm (0.05 in) in length, and they are deposited by the fly in a suitable place for development, usually dead and decaying organic material, such as garbage, carrion, or feces. Within a day, larvae (maggots) hatch from the eggs; they live and feed where they were laid. They are pale-whitish, 3 to 9 mm (0.12 to 0.35 in) long, thinner at the mouth end, and legless; a hook near the mouth is used for eating bacteria. Larval development takes from two weeks, under optimal conditions, to thirty days or more in cooler conditions. The larvae avoid light; the interior of heaps of animal manure provide nutrient-rich sites and ideal growing conditions, warm, moist and dark.
At the end of their fourth instar, the larvae crawl to a dry, cool place and transform into pupae. The pupal case is cylindrical with rounded ends, about 1.2 mm (0.05 in) long, and formed from the last shed larval skin. It is yellowish at first, darkening through red and brown to nearly black as it ages. Pupae complete their development in from two to six days at 35 °C (95 °F) but may take twenty days or more at 14 °C (57 °F).
When metamorphosis is complete, the adult fly emerges from the pupa. To do this, it uses the ptilinum, an eversible pouch on its head, to hammer open the end of the pupal case. The adult housefly lives for from two weeks to a month in the wild, or longer in benign laboratory conditions. Having emerged from the pupa, it ceases to grow; a small fly is not necessarily a young fly, but is instead the result of getting insufficient food during the larval stage.
Male houseflies are sexually mature after 16 hours and females after 24. The male initiates the mating by bumping into the female, in the air or on the ground, known as a "strike". He climbs on her thorax and if she is receptive, a courtship period follows, involving the female vibrating her wings and the male stroking her head. The male then reverses onto her abdomen and the female pushes her ovipositor into his genital opening; copulation, with sperm transfer, lasts for several minutes. Females normally mate only once and then reject further advances from males, while males mate multiple times.
The larvae depend on warmth and sufficient moisture to develop; generally, the warmer the temperature, the faster they will grow. In general, fresh swine and chicken manure present the best conditions for the developing larvae, reducing the larval period and increasing the size of the pupae. Cow, goat and horse manure produce fewer, smaller pupae, while fully composted swine manure, with a water content of under 40%, produces none at all. Pupae can range from about 8 to 20 milligrams (0.0003 to 0.0007 ounces) under different conditions.
The life cycle can be completed in seven to ten days under optimal conditions but may take up to two months in adverse circumstances. In temperate regions, there may be twelve generations per year, and in the tropics and subtropics, more than twenty.
Ecology
Houseflies play an important part in the ecosystem in breaking down and recycling organic matter. Adults are mainly carnivorous; their primary food is animal matter, carrion and faeces, but they also consume milk, blood, other body fluids, sugary substances, and rotting or fermenting fruit and vegetables. Solid foods are softened by saliva before being sucked up. Adult flies also drink water. As well as feeding on carrion and dung, the larvae will consume moist paper, cotton and wool in close contact with their main foodstuffs. Houseflies have a mutualistic relationship with the bacterium Klebsiella oxytoca. This bacterium can live on the surface of the housefly eggs and has a deterrent effect on the fungi growing in manure, thus benefiting the fly larvae which are competing with the fungi for nutrients.
Adult houseflies are diurnal and rest at night. If inside a building after dark they tend to congregate on ceilings, beams and overhead wires, while out of doors, they crawl into foliage or long grass, or rest in shrubs and trees or on wires. In cooler climates, some houseflies will hibernate in winter, choosing to do so in cracks and crevices, gaps in woodwork and the folds of curtains. They arouse in the spring when the weather warms up and search out somewhere to lay their eggs.
Houseflies are preyed on by many different predators including birds, reptiles, amphibians, various insects and spiders. The eggs, larvae and pupae all have their own parasites and parasitoids, with many different species of parasite having been associated with houseflies under different conditions. Some of the more important are the parasitic wasps Muscidifurax uniraptor and Sphalangia cameroni; these lay their eggs in the fly larvae and their offspring complete their development before the adult flies emerge from the pupae. Hister beetles feed on housefly larvae in manure heaps and the predatory mite Macrocheles muscae domesticae consumes housefly eggs, each mite eating twenty eggs per day.
The pathogenic fungus Entomophthora muscae causes a fatal disease in houseflies. After infection, the fungal hyphae grow throughout the body killing the fly in about five days. When it is critically ill, it tends to crawl to a high point, straighten its hind legs and open its wings, a behaviour that ensures that the fungal spores which are soon produced are dispersed as widely as possible. The housefly also acts as the alternative host to the parasitic nematode Habronema muscae that attacks horses.
Distribution
The housefly is probably the insect with the widest distribution in the world; it is largely associated with man and has accompanied him around the globe. It is present in the Arctic, where Linnaeus noted its presence in Lapland and Finland, and the tropics, where it is abundant. It is present in all populated parts of Europe, Asia, Australasia and the Americas.
Evolution and taxonomy
Even though the order of flies (Diptera) is much older, true houseflies are believed to have evolved in the beginning of the Cenozoic era. The housefly's superfamily, Muscoidea, is most closely related to the Oestroidea (blow flies and allies), and more distantly to the Hippoboscoidea (louse flies and allies). They are thought to have originated in the southern Palearctic region, particularly the Middle East. Because of their close, commensal relationship with humans, they probably owe their worldwide dispersal to co-migration with humans.
The housefly was first described as Musca domestica in 1758 by the Swedish botanist and zoologist Carl Linnaeus in his Systema naturae, and it is still classified under that name. A more detailed description was given in 1776 by the Danish entomologist Johan Christian Fabricius in his Genera Insectorum.
The cladogram is based on the FLYTREE project.
Within the Muscoidea, the family of the housefly, Musca, is the Muscidae, with relationships as shown on the following cladogram from Couri and Carvalho 2003.
Relationship with humans
Flies are a nuisance, disturbing people at leisure and at work, but it is principally because of their habits of contaminating foodstuffs that they are disliked. They alternate between breeding and feeding in dirty places with feeding on human foods, during which process they soften the food with saliva and deposit their faeces. This is a health hazard.
As a disease vector
Houseflies feed on liquid or semiliquid substances beside solid material which has been softened by saliva. They deposit faeces frequently and regurgitate semi-digested food. Although they are domestic flies, mainly confined to human habitations and farm buildings, they can fly for several miles from the breeding place.
Houseflies carry a wide variety of organisms on their hairs, mouthparts, vomitus and faeces. Parasites carried include cysts of protozoa e.g. Entamoeba histolytica, Giardia lamblia and eggs of helminths, e.g., Ascaris lumbricoides, Trichuris trichiura, Hymenolepis nana, Enterobius vermicularis. Houseflies are capable of carrying over 100 pathogens, such as those causing typhoid, cholera, salmonellosis, bacillary dysentery, tuberculosis, anthrax, ophthalmia and pyogenic cocci. Disease-carrying organisms on the outside surface of the fly may survive for a few hours, but those in the crop or gut may still be viable several days later. There are usually too few bacteria on the external surface of the flies (except perhaps for Shigella) to cause infection and the main routes to human infection are through the fly's vomit and particularly its faeces.
In waste management
The ability of housefly larvae to feed and develop in a wide range of decaying organic matter is important for recycling of nutrients in nature. This could be exploited to combat ever-increasing amounts of waste. Housefly larvae can be mass-reared in a controlled manner in animal manure, reducing the bulk of waste and minimizing environmental risks of its disposal. Harvested maggots may be used as feed for animal nutrition.
Control
Flies can be controlled, at least to some extent, by physical, chemical or biological means. Physical controls include screening with small mesh or the use of vertical strips of plastic or strings of beads in doorways to prevent entry of flies into buildings. Fans to create air movement or air barriers in doorways can deter flies from entering, and food premises often use ultra-violet light traps that electrocute insects. Sticky fly papers hanging from the ceiling can also be effective. Another approach is the elimination as far as possible of potential breeding sites. Keeping garbage in lidded containers and collecting it regularly and frequently, prevents any eggs laid from developing into adults. Unhygienic rubbish tips are a prime fly-breeding site, but if garbage is covered by a layer of earth, preferably daily, this can be avoided.
Insecticides can be used. Larvicides kill the developing larvae but large quantities may need to be used to reach areas below the surface. Aerosols can be used in buildings to "zap" flies, but outside applications are only temporarily effective. Residual sprays on walls or resting sites have a longer lasting effect. Many strains of housefly have become immune to the most commonly used insecticides.
Several means of biological pest control have been investigated. These include the introduction of another species, the black soldier fly (Hermetia illucens), whose larvae compete with those of the housefly for resources. The introduction of dung beetles to churn up the surface of a manure heap and render it unsuitable for breeding is another approach. Augmentative biological control by releasing parasitoids can be used, but flies breed so fast that the natural enemies are unable to keep up.
In science
Because the somatic tissue of the housefly consists of long-lived post-mitotic cells, it can be used as an informative model system for understanding cumulative age-related cellular alterations. Agarwal and Sohal studied the level of the oxidative DNA damage 8-hydroxydeoxyguanosine (8-OHdG) in houseflies. They found that the level of 8-OHdG increased with age of the flies. They also found an inverse association of 8-OHdG level with life expectancy of the flies. They concluded that their results support the hypothesis that oxidative molecular damage is a causal factor in senescence (aging). These findings are in accord with the general view that oxidative DNA damage, particularly in post-mitotic tissues, is a principal cause of ageing.
The housefly is an object of biological research, mainly because of one remarkable quality: the sex determination mechanism. Although a wide variety of sex determination mechanisms exist in nature (e.g. male and female heterogamy, haplodiploidy, environmental factors), the way sex is determined is usually fixed within one species. The housefly is thought to exhibit several different mechanisms for sex determination, such as male heterogamy (like most insects and mammals), female heterogamy (like birds) and maternal control over offspring sex. Its exact mechanism of sex determination is unresolved, but sexual differentiation is controlled as in other insects by an ancient (highly conserved) developmental switch, doublesex, which is regulated by the transformer protein in many different insects.
In literature
The Impertinent Insect is a group of five fables, sometimes ascribed to Aesop, concerning an insect, in one version a fly, which puffs itself up to seem important. In the Biblical fourth plague of Egypt, flies represent death and decay. In Greek mythology, Myiagros was a god who chased away flies during the sacrifices to Zeus and Athena; Zeus sent a fly to bite Pegasus, causing Bellerophon to fall back to Earth when he attempted to ride the winged steed to Mount Olympus. In the traditional Navajo religion, Big Fly is an important spirit being.
More recently, William Blake's 1794 poem "The Fly", part of his collection Songs of Experience, deals with the insect's mortality, subject to uncontrollable circumstances, just like humans. Emily Dickinson's 1855 poem "I Heard a Fly Buzz When I Died" speaks of flies in the context of death. In William Golding's 1954 novel Lord of the Flies, the fly is however a symbol of the children involved.
References
External links
- House fly on the UF/IFAS Featured Creatures Web site
- The House Fly and How to Suppress It, by L. O. Howard and F. C. Bishopp. U.S. Department of Agriculture Bulletin No. 1408, 1928, from Project Gutenberg.
Source of the article : Wikipedia
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