Diptera (True Flies) - Biodiversity (Singapore)

Diptera is a large order containing more than 150,000 formally described and the actual species diversity is much greater, an estimated 1,000,000 species. There are estimated to be a total of about 19,000 species of Diptera in Europe, 22,000 in the Nearctic region, 20,000 in the Afrotropical region, 23,000 in the Oriental region and 19,000 in the Australasian region. The order includes house flies, blow flies, mosquitoes, gnats, black flies, midges, fruit flies and others. The suborder Nematocera includes generally small, slender insects with long antennae such as mosquitoes, gnats, midges and crane-flies, while the Brachycera includes broader, more robust flies with short antennae. Many nematoceran larvae are aquatic, while most brachyceran larvae tend to be terrestrial.

While most species have restricted distributions, a few like the housefly (Musca domestica) are cosmopolitan. Flies are often abundant and are found in almost all terrestrial habitats in the world apart from Antarctica. Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced mechanosensory organs known as halteres, which act as high-speed sensors of rotational movement and allow dipterans to perform advanced aerobatics.

Flies have a mobile head, with a pair of large compound eyes, and mouthparts designed for piercing and sucking (mosquitoes, black flies and robber flies), or for lapping and sucking in the other groups. Their wing arrangement gives them great maneuverability in flight, and claws and pads on their feet enable them to cling to smooth surfaces. Flies undergo complete metamorphosis; their eggs are often laid on the larval food source. The larvae, which lack true limbs, develop in a protected environment, often inside their food source. Other species like Metopia argyrocephala are ovoviviparous, opportunistically depositing hatched or hatching maggots instead of eggs on carrion, dung, decaying material, or open wounds of mammals. The pupa is a tough capsule from which the adult emerges when ready to do so. Diptera mostly have short lives as adults.

Diptera is one of the major insect orders and of considerable ecological and human importance. Flies are important pollinators, second only to bees and their Hymenopteran relatives. Flies may have been among the evolutionarily earliest pollinators responsible for early plant pollination. Fruit flies are used as model organisms in research, but less benignly, mosquitoes are vectors for diseases such as malaria, dengue, West Nile fever, yellow fever, encephalitis, and other infectious diseases. Houseflies, commensal with humans all over the world, and spread foodborne illnesses. Flies can be annoyances especially in some parts of the world where they can occur in large numbers, buzzing and settling on the skin or eyes to bite or seek fluids. Larger flies such as tsetse flies and screwworms cause significant economic harm to cattle. Blowfly larvae, known as gentles, and other dipteran larvae, known more generally as maggots, are used as fishing bait and as food for carnivorous animals. They are also used in medicine in debridement, to clean wounds.