Order: Diptera (‘two-winged’)
- Single pair of membranous wings
- hindwings modified as halteres
- suctorial mouthparts, piercing or non-piercing; large compound eyes
- tarsi, 5-segmented
- metamorphosis complete with egg, larval, pupal and adult stages.
Common Housefly (Musca domestica)
Description of the Common Housefly
- Adults, 6-8mm long with 13-15mm wingspan
- grey thorax with 4 longitudinal dark stripes
- basal half of abdomen buff-coloured and occasionally transparent at sides, with central dark band broadening to cover last abdominal segments; at rest, wings are spread
- venation shows a sharp upward bend of 4th vein at apical end; wide distance between the eyes on the female and narrow in the male.
Common houseflies are found everywhere, with a flight range of at least 8 kilometres (5 miles).
They are highly active indoors.
In colder climates breeding generally ceases before winter, and the flies overwinter either as pupae or adults. In warm environments Common houseflies remain active and reproduce throughout the year.
Life-Cycle of Common Housefly
Forty-eight hours after emergence as an adult, the female starts egg laying. During her adult life of 1-3 months she is capable of producing 4-5 batches of 100-150 eggs. The pearly-white cylindrical eggs, 1mm in length, are laid in moist decaying matter such as household refuse, compost or dung.
The eggs hatch in 8-48 hours, giving the smooth, white, legless maggot larvae. These burrow away from light, seeking an optimal temperature of 21 to 32°C, and after 3 moults reach maturity at a length of 10-12mm.
In the summer larval development may be completed within a few days, but in winter this process may take more than a month.
When mature, the larvae leave the breeding site for the cooler surrounding areas; e.g. soil. Here they develop as yellow, brown or black pupae 6mm long.
Depending upon conditions, adults emerge 3 days to 4 weeks later.
The full cycle is generally completed between one and 4 weeks, depending upon temperature.
It is clear that there is considerable potential for the development of huge populations.
Under temperate conditions as many as 12 generationsof flies may breed in one season whilst under tropical conditions even this rate of reproduction will be exceeded.
Significance of Common Housefly
Houseflies can transmit intestinal worms, or their eggs, and are potential vectors of diseases such as dysentery, gastroenteritis, typhoid, cholera and tuberculosis.
They will frequent and feed indiscriminately on any liquefiable solid food, which may be moist, putrefying material or food stored for human consumption.
Common houseflies liquefy food by regurgitating digestive juices and their stomach contents on to the food substance. This ‘liquid’ is then drawn up by the suctorial mouthparts and in so doing the insects pick up pathogenic organisms, which may collect on their bodies to be transferred on contact with other surfaces or survive passage through the gut to be deposited as fly spots. Fly spotting, produced when the insect feeds or defecates, results in rejection of contaminated farm produce, for example eggs, at point of sale.
Flies are frequently the subject of complaints to environmental health authorities, causing major problems where infestations overspill from breeding sites such as rubbish tips and animal houses.
The Lesser housefly makes longer flights and spends less time resting than the Common housefly.
Females of the species tend to remain near the breeding sites and only the males migrate.
For these reasons Fannia canicularis (Lesser Housefly) is less prone to transmit disease than Musca domestica, but large populations and similar feeding habits mean that this insect, too, has a considerable potential to act as a vector of disease. It has occasionally been implicated as a vector of intestinal or urinary myiasis.
Common Housefly Control
Flies have rapid, prolific breeding habits and high mobility. In order to break the life-cycle, control measures should be directed against larval and adult flies.
Satisfactory hygiene is necessary to limit potential breeding sites and food sources.
Domestic refuse should be stored in well sealed bins, for early removal to disposal sites.
High-risk material should be sealed in bags and burnt wherever possible.
Refuse tips should be covered with earth, to a depth of at least 230mm (9 inches), and then compacted, this will minimise larval emergence and promote fermentation temperatures at which larvae cannot survive.
Farm manure should be kept as dry as possible, especially in poultry houses, where leaking water feeders can provide ideal, moist breeding conditions.
The Biothermic method of storing dung involves compacting manure into a cuboid stack, a method particularly suited to horse manure. This form of storage promotes uniform, persistent fermentation throughout the dung, which is lethal to larvae. Tarpaulins can also be used to cover heaps, in order to prevent egg laying and conserve the heat of fermentation.
Entry of adult flies into buildings can be prevented by 1.18mm-mesh fly-screens (which can easily be removed for cleaning), air curtains, bead screens or self-closing doors equipped with rubber flaps.
Physical control using maggot traps
Maggot traps take advantage of the fact that larvae need to migrate from breeding sites to cooler surroundings in order to pupate. A simple trap consists of a concrete platform, on which manure or refuse is stored, surrounded by a water-filled moat in which migrating larvae are trapped.
In order to obtain the best results, insecticidal control measures should be integrated with good hygiene.