- Only the front pair of wings are used for flight (‘Di’ ‘ptera’ means two-winged). The hind pair of wings is reduced to tiny drum-sticks used as counter balances to the wings (halteres).
- They lack jaws, the basic pattern of the mouthparts being designed to suck moisture, nectar or honeydew off surfaces. However, some have adapted the structure for piercing in order to suck blood (reference to flies biting is not strictly correct).
- The life cycle is complete:- egg, larva, pupa and adult.
- In size they range from minute dots, less than 1 mm long, to giants 30 mm long, even in Britain.
What they do & where they live
- Between them they live in a huge range of place such as:- soil and leaf-litter, in leaves, stems, flower and seed heads of plants, moss, fungi, rotting wood, dung, water, and many are parasitoids as larvae or predatory as larvae or adults.
- They occur in all land habitats, and in shallow fresh and brackish water. There are even a few species in the marine inter-tidal zone.
Number of species- About 6,900 species live in Britain, the second largest order of insects.
- Worldwide, about 150,000 described species, but there must be many more, especially in the tropics.
It's amazing. Nearly 7000 species of flies, and they all have their special place in the web of life. Surprisingly few species are a major nuisance to man – far more are useful ones.
DIPTERA (Order of insects) = Flies
An immense Order with nearly 7000 species. These are the true flies with only two wings (rather than 4). The many different types include:-
(Nematocera), which mostly have long antennae composed of many segments and long legs. Examples are craneflies, gnats, mosquitoes and midges. Britain has over 2,600 species.
It's amazing: The phantom midge larva is the ultimate invisible killer-submarine. It is transparent and uses air bumbles in its body as buoyancy chambers; and it has huge 'monster from the deep jaws' to catch water fleas.
SOLDIERFLIES and ALLIES.
A loosely related group of families, including robberflies, bees-flies and horseflies. Britain has about 160 species.
It's amazing: Three species are parasites of spiders, a pretty unlikely occupation for a fly!
Most of them hover and most of them are attractive when sitting at flowers. A lot of them are the gardener’s friends since the larvae eat greenfly and other aphids. They are widely accepted as colourful 'nice flies'. Britain has about 270 species.
It's amazing. Some are such good mimics of bees and wasps that it is hard to tell the difference.
One of the fascinating things that flies do is to mine through between the outer layers of leaves to produce various shapes of narrow tunnels or hollowed out patches. It is of course the larvae that do the mining, and the many different species have their favoured plants. Some species mine in stems, even in bark or wood. The main family doing this is the Agromyzidae, but various other flies do the same. Fly mines tend to have relatively little frass (pellets of dung) compared with other leaf-mining insects such as micro-moths, tiny sawflies and tiny beetles.
It's amazing Intricate works of art produced by tiny flies, and the artist can often be identified without even seeing the fly.
Many flies may look rather drab, but these have pretty markings on the wings, and the body is also often patterned. The name is often applied to the family Tephritidae whose larvae live in plant stems, flowers and leaves but there are distinctive species in various other families as well. Britain has about 73 species of Tephritidae, and many picture-winged species in other families.
It's amazing: Picture-winged flies may often be seen waving their wings, males challenging each other for territory or trying to impress females.
This may sound bizarre, but there are flies which specialise in killing snails and slugs, at least that is what the larvae do for food. Snails are vulnerable on land and the edges of water. Many of these flies have distinctive wing markings. Britain has about 67 species.
It's amazing: The fly larva does not immediately kill a snail, which would rot fast, but feeds gradually on a living snail for as long as possible before consuming the vital organs. Sounds horrid, but its part of nature's check on being overwhelmed by snails.
ADVANCED PARASITIC FLIES
In evolutionary terms, the most advanced flies are nearly all parasites. The adult flies are often very alert and 'aware' in a fashion which makes their more primitive cousins seem relatively dim-witted. These include the family Tachinidae, which resemble extra-bristly house flies; these are parasites of moth caterpillars and various other invertebrates. Britain has about 250 species of Tachinidae.
It's amazing:- Some Tachinidae lay eggs are so small and tough, that when laid on leaves, they can be ingested without damage by a leaf-munching caterpillar.
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