AUGUST 2016 FLIES
One of the drawbacks of an English summer, apart from unpredictable weather, is flies. Apparently there are more than five thousand species in Britain which vary greatly in size. Some are useful, most are not. At least in England we’re not plagued with midges like Scotland or at risk of contracting malaria from mosquitoes although, having said that, it was rife in England’s marshes and fens until the late nineteenth century. A few such as hover flies, which look like small wasps and dart about as well as hovering, are beneficial to plants as pollinators while lacewings feed on aphids, mealy bugs and spider mites. Most flies however cause considerable harm. Perhaps the most familiar are house flies which show no inclination to go back outside once indoors. They are the major carriers of disease being attracted to food and faeces, are annoying when they settle on you and appear to be immune to fly spray (but not a swat!). Bluebottles/blowflies are also horrible but at least they oblige by going out the window when you open it. Fruit or vinegar flies also turn up indoors to aggravate us. In winter cluster flies seek to hibernate in lofts. It is they that appear from nowhere indoors on a sunny winter’s day. Often hibernating with them are minute yellow swarming flies. Outdoors in summer there are black flies which swarm round our heads and sometimes bite and several species which plague livestock. So called horse flies inflict very painful bites to both animals and humans. The males actually feed on nectar and pollen, it’s the females that go for blood – their mouthparts are like miniature knives which they use to slash through skin with a scissor-like motion. Clegs too are painful blood suckers. Greenbottles lay their eggs on a sheep’s dirty wool. This is known as ‘strike’ and the maggots when they hatch out eat their way into the sheep’s flesh. Large warble flies are parasitic with a most unpleasant life cycle. They lay their eggs on the forelegs of cattle and deer. When these hatch the larvae migrate through the body of the animal growing larger all the time and emerge through the skin along the back showing as large bumps from which huge maggots pop out. Thankfully warbles were eradicated from the UK in 1990. Less damaging but probably more stressful are autumn flies which plague cattle and horses by gathering round their heads in large numbers. They breed in animal dung as do khaki coloured dung flies which feed on any insects attracted to cowpats. Another familiar fly is the Crane fly, better known as ‘Daddy Long Legs’, a large, flying, long-legged insect which can sometimes be disturbed in their thousands when walking across grassland in late summer. They themselves do not bite although their larvae, better known as leatherjackets, cause untold damage beneath the ground by eating plant roots. The carrot fly and the frit fly, which can seriously damage cereals, are other major crop pests along with aphids, thrips and greenfly.