Bushflies (DPI Vic)

May, 1995 Bushflies AG0410 Richard Crow, Burnley ISSN 1329-8062 Expiry date: May, 1998 The bushfly (Musca vetustissima) is a native fly found all cattle, sheep, and native animals is preferred. Only fresh over Australia. It is often confused with the housefly. The dung is attractive and the female usually feeds on this bushfly does not bite but is a persistent outdoor pest that before laying her eggs. causes irritation to people and animals. An egg-laying female attracts other females, so many thousands of eggs may be laid in one place. The eggs hatch in less than eight hours in hot weather. The larvae quickly emerge, burrow into the dung and begin feeding. They grow rapidly, passing through three stages, each marked by shedding of the skin. The length of the larval period, like the egg stage, is controlled by temperature and takes about five days. Maggots of the bushfly cannot survive at temperature below 120C. The fully-grown larvae leave the dung at night and bury themselves in the soil where they form pupae. Adult bushfIles emerge from three to 18 days later. They reach Figure 1. The bushfly (Musca vetustissima) sexual maturity after about three days, but the females Appearance and identification mate and lay eggs only after obtaining a feed of protein, mainly from the dung and body fluids of animals. The adult bushfly is about 6 mm long and has one pair of colourless, transparent wings. The body is grey with black The adult bushfly lives for from two to 11 weeks, markings on the abdomen, of which the first segment is depending on temperature and availability of food and completely black. Two broad black bands run the length of water. A complete generation may take from one to three the thorax and usually split into a short fork near the head. weeks (Figure 2). These two bands help distinguish the bushfly from the somewhat similar housefly. Habits and importance The egg is creamy-white, elongated, slightly curved and Bushflies, especially females, are attracted to large nearly 2 mm long. The larva is a tapering, white, legless animals, including man, where they either settle on the maggot which is 10 mm long and yellowish when fully back or seek body fluids such as tears, sweat, saliva or pus. grown. The pupa is enclosed in a brown, barrel-shaped Their persistent presence creates a nuisance and they may case with round ends and about 5-6 mm long. transmit eye diseases, especially among stock. Bushflies are active only in the day and their activity Life-cycle corresponds with the rise and fall in air temperature. They Female bushflies may lay from one to five batches of prefer to be in direct sunlight and only enter buildings by between five and 50 eggs. The eggs are laid in crevices in accident when carried in on people's backs. animal dung or between the dung and the soil. The dung of

Adult fly lives several weeks Eggs hatch Larval stages (maggots) Larvae pupates Pupal stage Adult emerges Figure 2. The life cycle of a bushfly

Summer is the only time during which bushflies breed in The bushfly has several natural enemies such as sphecid Victoria. Temperatures below 120C are unfavourable for wasps, asilid flies, mites and nematodes (microscopic their survival, so they die out in winter in southern worms), but they are of minor importance in control. Australia. However, they breed all year round in some of Repellents that contain both di-N-propyl the warmer parts of Australia, for example, in areas just isocinchomeronate and N-octyl-bicycloheptene south of Alice Springs, near the border of Queensland and dicarboximide (all of the common brands) have been New South Wales, and south of Carnarvon in Western found to give some protection and they do allow outdoor Australia. activities to be carried out in relative peace; one Each spring, north winds carry these flies south, even as application can give protection for several hours. They are far as Tasmania. The flies can build up big populations in available as aerosols, pump sprays, gels, creams and roll- Victoria over summer, occasionally reaching plague ons. proportions in some areas if conditions are suitable. When applying repellents, cover all exposed skin with a good application of repellent. Do not cover lips, eyes and Control nostrils. Many repellents soften plastic and paint and so The breeding sites of the bushfly are so widespread that should not be put on spectacle frames. The concentration biological control is the only practical approach. The of the repellent in gels, creams and roll-ons is generally CSIRO has introduced dung beetles into the primary greater than that in aerosols and pump sprays. breeding area in the northern states and it is hoped that Fly veils give some relief from flies but they are generally these will reduce the number of flies by making dung thought to be inconvenient and unattractive. unsuitable for breeding of bushflies. The methods used to control houseflies will also control Imported species are needed because the native Australian any bushflies that accidentally stray indoors. beetles cannot cope with dung of large introduced animals such as cattle. Dung beetles that should be able to breed Further information and survive in southern states are now being introduced Further information about flies and their control can be and tested. When they are established, they may reduce the obtained from the Fly Suppression Unit, Burnley Gardens, abundance of bushflies in summer. Swan Street, Burnley, Vic. 3121. Telephone 810 1511. Sanitation procedures have little effect on control of the bushfly because it breeds only in animal dung.

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