MOSQUITO (diminutive of the Spanish tnosca, a tly), a name applied to insects of the dipterous family Culicidce. Mosquitoes are cosmopolitan, only a few oceanic islands, deserts and mountain tops being free from them. Frequently they occur in vast swarms, and they abound equally in arctic regions, as Alaska and Greenland, and in the tropical swamps of Africa and South America, while at many intermediate points they are intolerable pests. Vertically they range from the seashore to altitudes of at least 13,000 feet. While many species are local, others are very widely dis tributed. Typical mosquitoes have the follow ing characteristics: The mouth is provided with a prolonged, suctorial, piercing proboscis ; the greater part of the body and head and portions of the wings and legs are covered with scales which determine the color pattern; the compli cated venation of the wings is also highly characteristic. These features distinguish mos quitoes from the related midges (Chironomide and Cecidomyidee) and the black flies (Si mulidce) ; and from the crane-flies (Tipulace) which inspire most of the stories of gigantic mosquitoes. • Not less than 22 genera and 350 species are now known. The species are based largely upon differences in the form and ar rangement of the scales and the resulting coloration, the form of the foot-claws, etc.
The typical life-history of a mosquito is as follows: The eggs are depos ited at night in or (rarely) near shallow water, usually fresh but in the case of a few species brackish or salt. After one or a few days they hatch into legless, aquatic larva, popularly known from their activity as "wig glers." These have the mouth provided with small jaws for browsing at the bottom, and with brushes of hairs whose movements induce currents in the water and bring to the mouth floating particles or minute plants and animals which serve as food. The thorax is more or less swollen, and the abdomen 'slender and nine-jointed, with the last, or anal, segment bearing two pairs of leaf-like appendages and a more or less conspicuous fan of spreading hairs. On the dorsum of the eighth segment is a pair of spiracles, or breathing-pores, usually borne at the end of an elongated tube or siphon. By
their active wiggling the larva come frequently to the surface and breathe, and then sink by gravity lazily to the bottom. After one or more weeks the larva molt finally and transform into pupa, which have the head and thorax closely united, and the latter greatly enlarged, with the form of the future legs and wings apparent At the tail end is a pair of fin-like expansions; while the respiratory organs, instead of being near the end of the abdomen, have the form of a pair of large mouthed tubes or funnels on the dorsum of the thorax. Like the larva the pupa are active wigglers, but, unlike them, are buoyant and naturally float at the surface with the respiratory funnels uppermost and exposed. When alarmed they display much activity and wiggle violently toward the bottom. The imagoes escape from the pupal investments at the surface, and windrows of cast-off skins are thrown up at the water's edge. The males, which transform first, hover in little clouds and are sought by the females. In the males the antenna are broad and feather-like, in the females slender and simply hairy, The dura tion of the period of aquatic life varies with the species and temperature; in our common Culex pungens it may be only 10 days, so that many generations may be produced during a favorable season. The winter may be passed in any stage from egg to adult, all of which pre extremely resistant to cold, and the aquatic stages capable of withstanding repeated freez ing and thawing. The hibernating imagoes, which are found in houses and other sheltered places, may become active on warm days and in the case of Anopheles, at least, are chiefly fertilized females. Mosquitoes have many natural enemies.' The aquatic stages are preyed upon by carnivorous fishes, water-newts larva of dragon-flies and aquatic beetles and leeches. Vast numbers of the flying insects are destroyed by night-hawks and bats, and during the day they are pbonced 'tipon by hornets and -other carnivorous insects, and up by swallows and swifts as they skim they meadows. Of their parasites the recent discovered worm, ,Agammomermis culicis, is sidereci to exert an important checking influence in ,smne Years.