Houseflies are often considered a nuisance, disturbing people while at leisure and at work, but they are disliked principally because of their habits of contaminating foodstuffs. 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 feces, creating a health hazard. However, housefly larvae are as nutritious as
fish meal, and could be used to convert waste to
insect-based animal feed for
farmed fish and
livestock. Housefly larvae have been used in traditional cures since the
Ming period in China (1386 AD) for a range of medical conditions and have been considered as a useful source of
chitosan, with antioxidant properties, and possibly other proteins and polysaccharides of medical value. Houseflies have been used in art and artifacts in many cultures. In 16th- and 17th-century European
vanitas paintings, houseflies sometimes occur as
memento mori. These depictions,
Musca depicta, are also used for other effects as in the Flemish painting, the
Master of Frankfurt (1496). Housefly amulets were popular in ancient Egypt.
As a disease vector Houseflies can fly for several kilometers from their breeding places, carrying a wide variety of organisms on their hairs, mouthparts, vomitus, and feces. Parasites carried include cysts of
protozoa, e.g.
Entamoeba histolytica and
Giardia lamblia and eggs of helminths; e.g.,
Ascaris lumbricoides,
Trichuris trichiura,
Hymenolepis nana, and
Enterobius vermicularis.
bacillary dysentery,
tuberculosis,
anthrax,
ophthalmia, and pyogenic cocci, making them especially problematic in hospitals and during outbreaks of certain diseases. Disease-causing organisms on the outer surface of the housefly may survive for a few hours, but those in the crop or gut can be viable for several days. A number of bacterial endosymbionts have however been detected in sequence-based identification from whole genome sequences extracted from flies, the greatest numbers being detected in the abdomen. In the early 20th century, Canadian public health workers believed that the control of houseflies was important in controlling the spread of tuberculosis. A "swat that fly" contest was held for children in Montreal in 1912. Houseflies were targeted in 1916, when a
polio epidemic broke out in the eastern United States. The belief that housefly control was the key to disease control continued, with extensive use of insecticidal spraying well until the mid-1950s, declining only after the introduction of
Salk's vaccine. In China,
Mao Zedong's
Four Pests Campaign between 1958 and 1962 exhorted the people to catch and kill houseflies, along with rats, mosquitoes, and sparrows.
In warfare During the
Second World War, the Japanese worked on
entomological warfare techniques under
Shirō Ishii. Japanese Yagi bombs developed at Pingfan consisted of two compartments, one with houseflies and another with a bacterial slurry that coated the houseflies prior to release.
Vibrio cholerae, which causes cholera, was the bacterium of choice, and was used by Japan against the Chinese in
Baoshan in 1942, and in northern
Shandong in 1943. The Baoshan bombing produced epidemics that killed 60,000 people in the initial stages, reaching a radius of which finally took a toll of 200,000 victims. The Shandong attack killed 210,000; the occupying Japanese troops had been
vaccinated in advance.
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 that uses a housefly in a
Renaissance allegory of touch theme Houseflies 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 houseflies into buildings. Fans to create air movement or air barriers in doorways can deter houseflies from entering, and food premises often use
fly-killing devices; sticky
fly papers hanging from the ceiling are 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 housefly-breeding site, but if garbage is covered by a layer of soil, preferably daily, this can be avoided.
Resistance to
carbamates and
organophosphates is conferred by variation in
acetylcholinesterase genes. 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.
In science 's illustration of "The Fly" in
Songs of Innocence and of Experience (1794) The ease of culturing houseflies, and the relative ease of handling them when compared to the fruit fly
Drosophila, have made them useful as model organism for use in laboratories. The American entomologist
Vincent Dethier, in his humorous
To Know A Fly (1962), pointed out that as a laboratory animal, houseflies did not trouble anyone sensitive to animal cruelty. Houseflies have a small number of chromosomes, haploid 6 or diploid 12. The housefly is an object of biological research, partly for its variable
sex-determination mechanism. Although a wide variety of sex-determination mechanisms exists in nature (e.g. male and female
heterogamy,
haplodiploidy, environmental factors), the way sex is determined is usually fixed within a
species. The housefly is, however, thought to exhibit multiple mechanisms for sex determination, such as male heterogamy (like most
insects and
mammals), female heterogamy (like birds), and maternal control over offspring sex. This is because a male-determining gene (
Mdmd) can be found on most or all housefly chromosomes. Sexual differentiation is controlled, as in other insects, by an ancient
developmental switch,
doublesex, which is regulated by the
transformer protein in many different insects.
Mdmd causes male development by negatively regulating
transformer. There is also a female-determining
allele of
transformer that is not sensitive to the negative regulation of
Mdmd. The antimicrobial peptides produced by housefly maggots are of pharmacological interest. In the 1970s, the aircraft modeler Frank Ehling constructed miniature balsa-wood aircraft powered by live houseflies. Studies of tethered houseflies have helped in the understanding of insect vision, sensory perception, and flight control.
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, while the
Philistine god
Beelzebub's name may mean "lord of the flies". 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.
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.
Ogden Nash's humorous two-line 1942 poem "God in His wisdom made the fly/And then forgot to tell us why." indicates the debate about the value of biodiversity, given that even those considered by humans as pests have their place in the world's ecosystems. == References ==