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Order - DIPTERA
(Greek, di = twice; pteron = wing)
Common Names: flies, crane flies, mosquitoes, midges, sandflies
Distribution: Cosmopolitan
Suborders: Nematocera and Brachycera

Description
All winged species of flies are distinguished by having only one pair of functional wings. The members of the order have a pair of membranous forewings used for flight while the hind wings are modified to form short, club-like structures called halteres. Halteres are used as balancing organs during flight. Some dipteran species are wingless throughout their life cycles and their position within the order must then be decided on using other aspects of their structure and life cycle. Well developed compound eyes are present. The adult body is often hairy and depending on the species, hairs may be few or abundant, short or long. Adult mouthparts are typically modified for sucking or sponging up fluids, but may also be adapted for piercing. Dipteran mouthparts are complex structures composed of a number of parts (e.g. labium, stylets, labellum, etc.).

Larva
All members have a metamorphic life-cycle: egg-larva-pupa-adult. The larvae of most flies are legless maggots. Free-swimming mosquito larvae are called wrigglers and these possess a well defined head and mandibles.

Members
Crane flies, blow flies, bee flies, dung flies, house flies, bush flies, robber flies, march flies, fruit flies, vinegar flies, mosquitoes, midges, gnats.

Food
Flies and mosquitoes feed on a wide variety of materials mostly involving fluids e.g. blood, dung fluids, plant or animal body exudates. When solids are consumed the flies often use saliva to partially digest or dissolve the solid before it is lapped up by the proboscis (mouthparts).

Importance
Flies and mosquitoes are one of the most successful insect orders with perhaps 250,000 species. They are immensely important as transmitters of disease and parasites. Human diseases include: sleeping sickness (tse-tse fly); malaria, filaria, yellow fever, dengue fever, Murray valley encephalitis (mosquitoes); dysentery, ophthalmia, cholera, and typhoid fever (house fly). Millions of dollars worth of damage to fruit crops (together with equally large costs of sprays to protect the crops) are caused by fruit flies of various kinds. Blow flies, screw worm flies and buffalo flies attack open wounds on animals, burrow into the animal tissues or suck blood from the animal. This requires expensive methods to combat their predations. Bot-flies parasitise horses and other animals by laying eggs on the animal’s coat. During grooming, the eggs are swallowed. The eggs hatch in the stomach where maggots attach themselves by mouth hooks and feed on blood. On maturity, the larvae pass out in the faeces, pupate and emerge as adult flies.