Page:The American Cyclopædia (1879) Volume VIII.djvu/58

 10 GNAT appendage on each side of the prothorax Other genera, ill-characterized for the most thaVeb^n added by modern systematists. the names gnat and mosquito are also given in ne places to members of the family tipulada* ; TnTour own mosmiitoes belong to several irenera, among which is the genus culex, prop- erly confined to the more northern regions of the continent. Dr. Harris mentions five species ,,f rnler and one of anopheles as found in New Enffland ; to these many species and several genera must be added. Some species are ac- tive by day, others only by night, but both are equally fond of human blood; the former are found principally in marshes and damp woods and rarely in houses, and are of more brilliant colors than the nocturnal species. The males with plumed antennae do not annoy us by their bites, but simply flit from flower to flower, sipping the dew and sweet juices, requiring but little if any food, propagating their species, and soon after perishing. The female gnats are most persistent biters and annoying mu- sicians, at almost all seasons of the year ; from the tropics to Lapland and arctic America, man is obliged to adopt some contrivance to protect himself from their attacks, either the thick coat of grease of the northern regions, the sand bed of the tropics, the smoky smudge of the woods, or the mosquito bars and curtains of civilized life. Gnats have been known to ap- pear in such swarms as to constitute an insect plague, darkening the air like clouds of smoke, arresting the progress of invading armies, and rendering whole districts for the time uninhab- itable; attacking not only man but beasts, and, even when not biting, filling every crack and corner with their countless multitudes. When we consider the immense number of these insects, and the comparatively small proportion which can ever taste human blood, we must admit, what experiments with sweetened fluids have confirmed, that vegetable juices form the food of the greater number of females, and perhaps the natural food of all ; many males probably do not eat at all. The sucking apparatus is admirably contrived for obtaining fluids, animal or vege- table, and these insects are provided with sucking stomach independent of the proper di gestive cavity. The sucker is well describee and figured by Reaumur in his "Memoirs;' the flexible sheath gives support to the lancets while they penetrate the skin ; the point of the combined lancets is sharper than the finest needle, so that the size of each of the severa weapons most be very small ; the wounds made by this instrument would be insignificant, were it not for an irritating secretion from the pro boacia, which in some delicate skins produce obstinate itching, and, in rare instances, even irritable ulcers. The metamorphoses whicl gnats and mosquitoes undergo are very curious The eggs are deposited in almost any natura or artificial receptacle for fresh water, and ar arranged in a boat-shaped form ; fixing herself >y the four anterior legs to some object at the urface of the water, the female crosses her lind legs in the form of the letter X ; bringing he latter close to the end of the body, on a evel with the water, the first egg is received ind retained in place by the crossed legs ; as he eggs are extruded they are placed side by ide vertically, adhering firmly together by the glutinous substance which covers them ; when he stern of the egg raft is properly raised, it s pushed further from the body by the succeed- ng ova, always retained in place by the legs on the sides ; when the raft is about half made and its shape is determined, the legs are un- jrossed and placed parallel, and the prow of .he boat is narrowed and raised like the stern. The boat is always of the same shape, contain- ng from 250 to 350 eggs, and is abandoned by .he mother to the mercy of the winds and waves, which can neither sink, wet, nor break t up ; even a temperature below freezing can- not destroy the life within these eggs. The larvro some out in a few days from the lower end of 1. Wing of gnat, showing nervures and small cells. 2. Ter- mination of abdomen of male. 8. Termination of abdo- men of female. 4, 5, 6. Modes of operation of gnat's sucker. 7. Gnat's eggs. 8. Boat of gnat's eggs. the eggs, which are arranged somewhat like the seeds of the ripe sunflower, and the empty shell boat is soon destroyed by the weather. The larvae of gnats and mosquitoes are the well known " wigglers " seen in warm wea- ther in almost every collection of standing water; they remain, as it were, suspended from the surface of the water, head downward, breathing air by means of a respiratory tube which goes off at an angle from near the end of the body, communicating with the tracheae ; the tube and the terminal joint are provided with radiating hairs ; the head is round, dis- tinct, with antennae and ciliated organs which keep up a constant current of water toward the mouth, and bring within their reach the minute animalcules on which they feed ; the thorax and ten-jointed abdomen are furnished with lateral pencils of hairs. If disturbed, these larvae quickly wriggle to the bottom, but soon come again to the surface and suspend themselves by the respiratory tube. Some species are comparatively free from hairs in