True flies are insects of the order Diptera. They possess a pair of wings and a pair of halteres, derived from the hind wings. Although many insects are termed "flies," but only those having one pair of wings distinguish true flies from other insects with "flies" in their names, such as mayflies, dragonflies, damselflies, fireflies, caddisflies or butterflies.

In other word, true flies are written as separate words, such as house flies, moth flies, sand flies, fruit flies, etc. True flies are of medical important as they serve as both biological and mechanical vectors in transmitting diseases, for instant typhoid, cholera, dysentery, leishmaniasis, onchocerciasis, trypanosomiasis, myiasis, etc.

House flies breed all over the world in and around dwellings occupied by humans and animals, rubbish dumps in fact anywhere where there is decaying organic matter. It has been suggested that this fly came originally from Africa but nowadays it has followed us to all parts of the earth.

House flies undergo a complete metamorphosis with distinct egg, larva or maggot, pupal and adult stages. Warm conditions are generally optimum for the development of the house fly, and it can complete its life cycle in as little as seven to ten days, and adult flies can live up to one to two months.

House fly populations can literally explode in just a few short weeks.

Moth Fly / Drain Fly / Sewer Fly

Moth flies are known as a nuisance pest. They are small with short, hairy bodies and wings giving them a "furry" moth-like appearance.

The adults have long antennae and the wings are leaf-shaped. Adult Psychodidae are typically nocturnal and associated with damp habitats.

The larvae of the subfamilies Psychodinae, Sycoracinae and Horaiellinae live in aquatic to semi-terrestrial habitats, including bathroom sinks; some species are commonly nuisance pests in bathrooms.

Sand Fly

Sand fly may refer to members of the subfamily Phlebomotominae, they are the primary vectors of leishmaniasis and pappataci fever, both diseases are confusingly referred to as sand fly fever. However, there is no indigenous reported case of the mentioned disease in Malaysia. Sand flies are weak fliers, biting is restricted to areas where suitable breeding sites occur.

Most biting occurs outdoors but a few species also feed indoors. Most species are active at dawn and dusk and during the night, they may attack in the daytime if disturbed.

They usually rest in dark and humid sites, such as tree holes, caves, houses and stables; other resting places near houses are crevices in walls, stacks of firewood, bricks and rubbish.