Bayer Environmental Science

Fly Biology

Believe it or Not	Valuables
Flies cannot chew. Flies have mouth parts that absorb food like a sponge. Their food has to be in a liquid form in order for them to eat it. They have a tongue shaped like a drinking straw to slurp up their meals. Flies that eat nectar or blood do so by using their tongue which is called a proboscis. Even flies that eat other insects do so by sucking out the insides of their victims. When a housefly lands on our food, it vomits on the food. The digestive juices, enzymes, and saliva in the vomit begin to break down and dissolve the food. The fly can then suck up the liquid food with its sponge-like mouth parts. If flies eat food from garbage cans or any other source of contaminated food, some of those germs stick to the fly's mouthparts and when the fly vomits on its next snack (your sandwich?), it transfers some of those germs.	Stable fly, Stomoxys calcitrans. Description: Similar to a house fly in size, ca. 5/16 inc long; a gray fly with distinct black spots on the abdomen. A slender, black, piercing mouthpart projects forward from the bottom of the head. Domestic animals affected: Cattle, swine, horses, sheep, goats, dogs; nuisance pest in poultry units. Damage caused: Annoyance from painful bites, blood loss; reduced milk production, feeding efficiency, and rate of gain; may transmit equine infectious anemia (swamp fever), porcine eperythrozoonosis, vesicular stomatitis of cattle and horses, and a mechanical vector of pathogens including anthrax, brucellosis, Salmonella, and others. Development: Complete metamorphosis: egg three larval instars (maggots), pupa, and adult. Generational time: Typically 3 to 4 weeks. Oviposition site: Fermenting grass clippings, compost piles, spilled feed, manure- and urine-contaminated hay or straw, manure (especially that which is over 3 weeks old). Larval habitat, feeding: Larvae feed in substrate from the oviposition site, taking nutrients primarily from the microbial flora and fauna therein. Adult habitat, feeding: Off host, stable flies prefer shelter from wind, mostly within 3 feet of ground level; seek host animals and suck blood once or twice daily, preferring legs and feet of most mammals (including humans) and ears of swine and dogs; stable flies usually orient themselves with their tail end toward the ground while on a host; daytime biters. Method of dispersal or infestation: strong fliers, stable flies sometimes 'migrate' many miles; they'll find a host in sunshine or deep shade.
	Facing Facts
	The Common House Fly, Musca domestica. This species is probably the most familiar and certainly the most widely distributed of all insects. It has accompanied man everywhere and has adapted itself to breeding in a wide variety of rejected food and excrement of man and his domestic animals. This species is classified in the family MUSCIDAE in which are placed a number of seemingly diverse forms with an even more diverse range of biology. Appearance: The adult flies are 7-8mm in length and greyish in colour, with four narrow black stripes on the thorax. Males have a pair of yellowish patches at the base of the abdomen. Life-cycle: The eggs are laid in almost any vegetable or animal matter provided that it is not too dry and can be readily swallowed and digested by the larvae. Stacks of fermenting horse-dung are frequently used for breeding but breeding will take place freely in human faeces, pig dung and household refuse in unemptied dustbins. When egg-laying takes place in dung the latter must not be more than 72 hours old. Adult flies live from 4 to 12 weeks. In the early summer there is a rapid re-colonization of all available breeding sites. Egg: The eggs are about 1 mm long, glistening white, and are laid in batches of 120 to 150 by the female fly, which may eventually produce a total of 600 to 900 eggs over a period of from 4 to 12 days. The time taken for the eggs to hatch varies according to temperature from about 8 hours to 3 days. Larva: The larva is white, legless and conical in shape, tapering at the head end. In warm weather it may be fully developed in 3 days, reaching 10 to 12 mm in length, but under less satisfactory conditions it may take 8 weeks to complete its development. When fully fed, the maggot, as the larva is known, appears waxy and ivory yellow in colour, and it abandons its larval environment in search of a cooler and drier place in which to pupate. The larva may travel considerable distances before it finds a suitable spot and will readily crawl up a smooth vertical surface if it is moist. Pupa: Pupation usually takes place in the soil where the larva may bury itself to a depth of 7-60cm, depending on the nature of the soil. The pupa is formed within the last larval skin and is barrel-shaped with rounded ends. It is at first pale yellow in colour but then darkens to reddish-brown and finally to dark brown or black. The pupal period varies from 3 to 28 days according to temperature. The total time taken to complete the life-cycle varies considerably with the temperature, humidity and the nature and abundance of the food supply. Economic importance: In the past, it would have been difficult to exaggerate the importance of the Common House Fly as a pest in the home. This is on account of its being a carrier of disease, brought about by its habit of flying between human faeces and human food. The disease organisms of typhoid, dysentery, summer diarrhoea, probably infantile paralysis and other diseases are transferred from faecal matter to food by vomit drops, in fly excrement or by organisms adhering to the fly's feet. The eggs of parasitic worms are also transferred in this latter way. In tropical and sub-tropical areas, in addition to these diseases, the House Fly is responsible for the spread of cholera, yaws and opthalmia. The adult fly feeds on both solid and liquid matter which can be lapped up by the sponge-like proboscis; the familiar 'fly-spots' are drops of liquid regurgitated and deposited on the surface by the fly.