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Fascinating Facts - Flies

Posted in Pest Advice on June 13, 2019

Some Fascinating Facts About Houseflies 

True flies are insects of the order Diptera. Diptera means two wings (originating from Greek di=two, and ptera=wing). Flies have a pair of functional wings for flight and a pair of vestigial (modified) hindwings called halteres which act like a gyroscope providing balance and a sense of position change.

The common housefly (Musca domestica) is the most common pest fly and it is this species that we will be considering.

  • Houseflies are the most common flies found in houses and other buildings. They are commensal with humans, i.e. they have a close association with us.
  • Houseflies are found from the arctic to the tropics and are common on all continents except Antarctica.
  • Houseflies have been found at heights of 2,000 metres in the air. It is probable that they have not flown to that height but have been carried up by up-draughts.
  • Adults are grey to black with four dark stripes running front to back on the thorax.
  • The fly body is hairy. They have brick red eyes that wrap around their head and give them a view up, down and behind them.
  • The housefly compound eye contains about 4,000 individual lenses each viewing at a slightly different angle, so they perceive multiple images of every point in their view.
  • Flies can process visual information and can detect movement more quickly than humans which is why we struggle to hit them with a fly swat.
  • Females are slightly larger in general and their eyes are set a little further apart.
  • Females usually mate only once and store the male sperm for fertilising eggs throughout her life.
  • Eggs are laid on moist decaying plant or animal material.
  • A female housefly lays up to 500 eggs in her lifetime.
  • Maggots hatch from the eggs and feed ravenously on the material for 2-5 days before pupating.
  • Fly maggots are an important part of the recycling of dead material.
  • When the maggots have fully developed (end of the fourth instar), they crawl to a dry, cool place and transform into red-brown pupae.
  • After metamorphosis in the pupae, the flies emerge and continue the cycle.
  • Flies emerge at full size and grow very little, if any, in adulthood. Smaller flies are the result of smaller, less well-fed maggots.
  • Male and female houseflies will be sexually mature within a day.
  • The females release a pheromone [(Z)-9-tricosene] which is attractive to the males although it is thought not to be released into the air and is only detected by the males on contact with the females.
  • The breeding potential of houseflies is enormous. Given no restrictions, a pair of flies could give rise to two hundred million trillion flies in 5 months. Soon there would be enough to cover the planet several metres deep.
  • Houseflies live for up to a month. They feed on a wide variety of foods.
  • Solid foods are partially digested and softened by their saliva because houseflies have mouthparts that can only sponge and suck up liquids.
  • The flies will stomp in the material to aid the softening and because they have taste receptors in their feet to taste the food. It is thought a fly foot is more than 10 thousand times more sensitive to sugar than our tongues.
  • Flies carry a variety of disease-causing organisms in their saliva, guts, faeces and exterior surfaces. They are therefore significant contaminators of food and transmitters of disease.
  • Houseflies are suspected of transmitting as many as 65 diseases to humans, including food typhoid fever, dysentery, cholera, poliomyelitis, yaws, anthrax, tularemia, leprosy and tuberculosis.
  • Flies can walk on the ceiling because their feet have hairy pads that produce a sticky substance which gives them excellent grip.
  • Housefly wings beat up to 1,000 times per second, but the majority of a fly’s buzz comes from the movement of air in and out of their breathing holes (spiracles) along the side of their body.
  • Nearly every time a housefly lands it defecates, leaving its faeces on the surface, often visible as fly spots.
  • As late as the 17th-century people thought maggots appeared spontaneously in decaying matter.

See here for information on how to get rid of flies and stop them pestering you and your family.

David Brittain

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