To access the photographs please click 'Diptera descriptions' on the header.

The Order Diptera are the True flies, with around 100,000 known species worldwide. They are sometimes known as 'Two-winged flies', because the forewings are fully formed and used for flight, whereas the hind wings are reduced to small knobs on short stems known as halteres. These are used for stability in flight, acting in a similar way to a gyroscope, balancing the fly while it flies. There are some exceptions to this description of Diptera wings, as a few species such as the Louse-flies (Hippoboscidae) are parasites with very reduced wings.

Diptera wings are usually clear with many veins. The wing veination is extremely variable and is often an important identification feature.

The antennae are also important identification features, at the sub-order level of classification and also at the species level. The number, size and shape of the segments and whether there is an arista (bristle) at the tip are all used to identify flies.

The Diptera have compound eyes (many facets or lenses to the eye). These are often so large that they meet at the top of the head, allowing them to detect very small movements over a very large area. The meeting of the eyes is often an indication that the fly is a male, although in some groups the females eyes are like this.

The mouth-parts of flies are also variable. With a few exceptions adult flies feed on liquids. Many species have mouth-parts consisting of pads used to mop up their food. They regurgitate digestive fluids to help with this process, which is part of the reason why house-flies are such important carriers of disease.

The females of many species feed on blood. Mosquitoes pierce the skin and suck the blood of their host with needle-like jaws, while others such as the horse-flies cut the skin with knife-like mouth parts, then mop up the blood. Large numbers of flies can debilitate their host, but perhaps worse is the spread of diseases such as malaria.

The larvae of the different species of Diptera are extremely variable in form and habit. The stereotype are the pale, wriggling, flesh eating maggots of blow-flies, but there are many others. Many are aquatic such as the larvae of the mosquito and the 'rat-tailed maggots' of some of the hoverflies, while others live within plants, or are parasites within the bodies of other insects, molluscs and even mammals.

The  larvae of Diptera do not have legs, but may have other appendages to help in mobility. Many also have biting jaws.

Diptera go through a pupal stage. The pupae may be similar to the familiar static pupae of the lepidoptera, or highly mobile as are the pupae of the mosquitoes.

The Diptera are of great importance to humans as economic pests, human parasites and vectors of disease. Despite this a large amount of their influence on man is positive as they are an effective biological control of other insect species, important plant pollinators and act as a massive waste disposal team clearing away corpses and rotting vegetation.

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To access the photographs please click 'Diptera descriptions' on the header.

Bibliography

Chinery, M., A Field Guide to the Insects of Britain and Northern Europe. (1973, Collins)

Chinery, M., Collins Guide to the Insects of Britain and Western Europe. (1986, Collins)

Erzinclioglu, Z., Blowflies.  Naturalists Handbooks 23 (1995, The Richmond Publishing Company)

Gilbert, F.S., Hoverflies Naturalists Handbooks 5 (1986, The Richmond Publishing Company)

Stubbs, A.E., Drake, M., British Soldierflies and their Allies (2001, British Entomological and Natural History Society)

Stubbs, A.E., Falk, S.J., British Hoverflies (1983, British Entomological and Natural History Society)

Stubbs, A.E., Chandler, P., A Dipterists Handbook (1978, The Amateur Entomologists Society)

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