**2. General features**

Dipteran insects are plentiful all over the sphere, in the tropics and subarctic, at oceanic level and on elevated peaks. These inhabit seashores to low-tide level, however, a small number move into deeper water and merely one or two midges are actually oceanic (*Pontomyia natans* Edwards in the Pacific). In contrast, wandering flies have been observed at much distant to marine. In general, flies vary in dimensions from robber flies more than 7 cm lengthy to midges of little more than 1 mm long. As a whole, the more-primitive flies (midges, mosquitoes, fungus gnats) are fragile insects and with delicate wings. The more-progressive flies (house flies, blow flies) are commonly bristly, thick and tough, and forceful fliers than gnats and midges.

Even though these have simply two wings, flies are among the greatest aerialists in the world of insects as they can fly forwards and backwards, turn at any place, hover, and even fly upside and down to land on a top boundary. Flies have the uppermost wing-beat rate than any of other animal. It may be as high as 1000 beats per second in case of some small midges. Generally, through the wing-beat frequency of a virgin female, male mosquitoes are attracted. Maggots of certain shore flies (family Ephydridae) live in uncommon habitations, which would destroy other insects. For instance, *Ephydra brucei* survives in warm geysers and springs wherever the water hotness go beyond 112°F. The petroleum fly *Helaeomyia petrolei* Coquillett

**Figure 1.** *Wetland ecosystem.*

develops in ponds of crude oil; and brine fly *Ephydra cinera* Jones, may live in extraordinary concentrations of salt [4].

The arista in the antenna of higher flies is an air speed indicator and it permits an insect to sense precisely just how fast it is moving. As black fly pupae mature, they become inflated with air. The pupal skin pops open upon emergence, and the fullygrown fly inside a bubble of air floats to water surface and it never even acquires its feet wet. The little scuttle fly *Megaselia scalaris* (Loew) is actually an omnivore. It has been cultured on paint emulsions, decaying vegetation, shoe polish, human dead body kept in formalin and even lung tissue from living people. As Diptera comprises the most ecologically diverse order of insects, swamps (wetlands ecosystem) resembling to this one (**Figure 1**) inundated by water and dominated by plant life, are great places to find its members.
