Flies and mosquitoes: Order Diptera

The Order Diptera (true flies) includes many common insects such as mosquitoes, midges, sand flies, blowflies and the House Fly.

Most of the insects we see flying around do so with four wings (two pairs), but dipterans (meaning 'two wings') use only one pair. The other pair of wings is reduced to club-like structures known as 'halteres' that they use for balance.

Common characteristics of the order include:

• One pair of wings (forewings)
• Hindwings reduced to club-like halteres
• A large and moveable head
• Compound eyes that are often very large
• Sucking, piercing and sucking or sponge-like mouthparts (all adapted for a liquid diet)
• The mesothorax (middle segment of the thorax or mid-body) is enlarged, with the prothorax and metathorax small
• Complete metamorphosis, with larvae (maggots) that are always legless, with chewing mouthparts or mouth-hooks, and that often pupate within a hardened case (puparium)

Suborder Nematocera

This group includes: crane flies, moth flies, midges, sand flies, mosquitoes, gall midges and fungus gnats.

This group is generally distinguished by having:

• A slender body with long legs and relatively long antennae with many segments of similar shape and size.
• Larvae with distinct heads that live in wet or aquatic environments, as well as some found in plant galls.

Suborder Brachycera

This group includes: march/horse flies, soldier flies, robber flies, bee flies, hover flies, fruit flies, vinegar flies, blowflies/ bluebottles, house/stable flies, flesh flies, tachinid flies and sheep ked/louse flies/wallaby flies.

This group generally has:

• A robust body with short (usually only 3 segments) antennae that are very variable in shape (arista - bristlelike structures near the tip of the antenna of certain flies - present or absent).
• Larvae with indistinct heads, often living in or on the soil, rotting vegetation or animal materials, with many that are predacious or parasitic.

There are many hundreds of species of flies in Sydney and without them life would certainly be different. Some are regarded as pests, but many beneficial species control populations of plants and animals, decompose waste material and provide links in a number of food chains.

Research in Australia and overseas is investigating the possibility of using maggots (fly larvae) in forensic science. After a murder or death, flies are the first insects to arrive on the scene and, by identifying and determining the age of the maggots, forensic scientists are able to estimate the time of death.

More than 7,000 dipteran species have been described in Australia but there are probably still three times as many yet to be discovered. There are more known fly species than fish, reptile, amphibian, bird and mammal species put together.