MOSQUITO, the name applied to species of blood-sucking flies belonging to the family Culicidae, or gnats, of the order Dip tera (q.v.). Prior to the year 1899 mosquitoes received very little attention from entomologists and relatively few species were known. At the end of the 19th century the researches of Ross in India and Grassi in Italy proved that mosquitoes are the agents concerned with the dissemination of malaria, and the establish ment of this important fact has led to the collection and study of these insects in all parts of the world. About 1,50o species of mosquitoes are now recognized and it is probable that the number of kinds actually existing is nearly 2,000.
Mosquitoes bear a close general likeness to many harmless midges (Chironontidae) but may be distinguished by the following characters. (I) The lower lip or labium is prolonged into an elon gate proboscis which forms a sheath enclosing the needle-like mouth-parts (fig. 1). (2) The presence of scales on the body, wings and other appendages. (3) The costal vein runs completely round the wing. (4) The antennae are densely plumose in the males and less hairy in the females, while the palpi project for wards and are not pendulous.
The family occurs in all parts of the world and although the tropics are much richer in genera and species than northern lati tudes, mosquitoes are abundant even in arctic regions. Under the latter conditions they are found during the short summer and often occur far from the haunts of man and even in regions unin habited by quadrupeds. In these lands they may go through a number of generations without tasting blood, nevertheless the blood-sucking instinct is so strong that they rarely fail to avail themselves of the first opportunity for responding to it that may present itself. As a rule the blood-sucking habit is confined to the female which differs from the male in possessing piercing mandi bles : the males largely feed on plant juices and the females apparently subsist upon a similar diet in the absence of blood.
Breeding Habits.—The early stages of all mosquitoes are passed in water, more usually fresh and less often salt or brackish.
water. Some domestic mosquitoes will breed in small accumula tions of water in discarded cans or other vessels : the larvae of other species occur in natural pools or ditches, while there are kinds which inhabit collections of water in hollow parts of trees or in the water-collecting receptacles of certain plants. Among other peculiar situations are pools flooded by the sea at high tides, mountain streams, wells, and the salt waters of Saharan oases. In each of these different habitats certain species of mosquitoes reg ularly breed and it therefore follows that knowledge of such facts is of vital importance in mosquito control. The eggs are usually deposited on the surface of the water and the number laid by a single female varies from 40-100 up to 300 or more. They may be deposited singly as in Anopheles or in compact masses or rafts as in the common Culex pipiens. The larvae are very active, with large heads and jaws and possess a pair of "brushes" which waft food-particles into the mouth. Their food chiefly consists of minute fragments of vegetable or animal matter, but some species are carnivorous, preying upon other, or even their own species.
Larvae of the group Culicinae have a prominent breathing syphon on the 8th abdominal segment and when taking in air this organ perforates the surface film, the creature itself hanging head downwards. In the group Anophelinae there is no respiratory syphon and they usually lie horizontally just be neath the surface film with the plate bearing the spiracles in free communication with the outside air. The pupae of mosquitoes are active creatures, crescentic in form, and breathe by means of a pair of respiratory trumpets which bfeak the surface film of the water when air is taken in.
The Anopheline mosquitoes generally have spotted wings and rest with the body and proboscis in one straight line, often obliquely with the supporting surface : the Culicinae, on the other hand, rest with the body parallel with the supporting surface and with the proboscis inclined at an angle with the thorax (fig. I).