Diptera: flies and mosquitoes

Characteristics
This is one of the largest insect orders in the world and includes many familiar insects such as mosquitoes, midges, sand flies, house flies and blowflies. Many species of Diptera are important due to the role they play in disease transmission, which includes such things as mosquitoes that spread malaria in many underdeveloped countries. Diptera can be distinguished by the following features:

• One pair of membranous wings

• Hind wings are reduced to small club like structures called halteres. The halteres are used as stabilisers during flight

• Sucking mouthparts, sometimes adapted for piercing e.g. mosquitoes

• large compound eyes

• short simple antennae, frilled or bushy in mosquitoes and crane flies

Comptosia insignis is a member of the BOMBYLIIDAE family. These flies superficially resemble bees due to their stoutly built bodies which are covered in hair and their long thin proboscis. This along with their flight habits have earned them the common name of bee flies. Adults can often be seen resting on or hovering over blossoms or patches of bare ground in sunny locations. Adult bee flies feed on nectar from a wide variety of flowers and may be important plant pollinators. Although little is known of the Australian species, the larvae of bee flies are believed to parasitise the larvae of other insects and may prey on the eggs in egg-masses of grasshoppers and locusts.

The small club-like halteres, as seen here are situated behind the much larger forewings. The base of halteres are flexible and when they are moved a fly or mosquito is able to control its flight. As the haltere bends at the base, a fly or mosquito can change flight speed or direction making them more manoeuvrable compared to many other flying insects.

Life Cycle
Flies have a complete life cycle and will mate while flying. The eggs are usually laid into suitable substrate or close by an appropriate food source. The larvae complete their development and pupate in the substrate where they were laid, which may be soil, organic matter, water, plant tissue or animal tissue.

Feeding
Adult flies are only able to ingest liquid foods due to their sucking and/or piercing mouthparts. In most species digestion is partially external and salivary secretions are introduced to liquefy the food and then the softened product is mopped up. Species such as mosquitoes and March flies pierce the skin of their prey with their proboscis and then suck up the blood.

The larvae of this insect order mostly feed on moist, decomposing food items such as carrion, fungi, dung and rotting vegetable matter although some are predators or parasites of other animals.

Habitat
Members of this order of insects are found in almost all types of terrestrial and freshwater habitats across Australia with forests and the margins of water bodies having the greatest diversity of species.