Page:The American Cyclopædia (1879) Volume VIII.djvu/59

 GNAT lis condition. After remaining in tlie larva state from five to fifteen days, according to the weather, and changing their skins two or three times, they are changed into pupro, called tum- blers from the manner in which they roll over and over in the water by means of the fin-like paddles at the end of the tail ; they are very quick in their motions, and swim with the head upward ; the respiratory openings are at the end of two tubes situated just behind the head, so that the little tumblers remain near the surface, head upward, to take in air ; in this state, which lasts five or ten days, accord- ing to circumstances, the insect takes no food ; the future gnat can be distinguished through the transparent covering of the pupa. When the perfect insect is ready to come forth, the pupa skin bursts open on the back toward noon on a warm, still, sunny day, and the head of the gnat makes its appearance, followed soon by the thorax ; this is a process of great dan- ger to the insect, as the slightest breeze would tip over the emerging form, and consign it to certain death in the water; after it has suc- ceeded in raising its body except the tail, and stands erect like a mast in the pupa shell boat, it extricates the front pair of legs and places them for support on the surface of the water ; the heavy and wet wings are now slowly un- folded, that the sun and air may dry them; this effected, the danger is over, and the other legs are drawn forth and extended on the edge .of the pupa case, the body is stretched out, the antennae and proboscis elevated ; by this time the wings are dry and fully expanded, and the insect flies off to revel among the flowers or in search of blood, according to the sex. The source of the buzzing noise has been much discussed by naturalists, and is still the subject of dispute ; it has been ascribed to the mouth by Mouffet, to the friction of the base of the wings against the chest by Kirby ; the wing- lets, the poisers, the motion of the wings, the rapid passage of air through the thoracic stig- mata, and the vibrations of the thorax from the contraction of the muscles of the wings, have been supposed to be the cause by other entomologists ; by whatever organ it be pro- duced, Siebold says it is always due to the ac- tion of voluntary muscles, and has no connec- tion with the respiratory system. It is prob- able that the sound is produced by the com- bined action of the wings and by the thoracic vibrations consequent thereon. It has been estimated by Baron de la Tour that the gnat vibrates its wings 50 times in a second. This very rapid movement probably depends on a peculiar form of muscle which has been detect- ed in the mosquito and other diptera ; the fibrillse are not bound together as in ordinary striated muscles, but are separate and parallel, formed by the aggregation in a linear series of little disks with regular interspaces ; contrac- tion of these independent fibrillae takes place by the approximation of these disks to each other ; some are contracting while others are GNEISENAU 51 relaxed, so that a constant and rapid move- ment of the wings is secured. It is certainly a remarkable example of the extent of mod- ern microscopic investigation, that the minute muscles of the wings and legs of the mosquito can be dissected and studied. Some of the bi- ting culicidoB do not make a boat of eggs, but string their ova end to end ; others deposit them in soft mud or in dry sand ; but all require moisture in the larva state. As the eggs are developed into the perfect insects in about three weeks, many broods are hatched in the course of the warm season, fully explaining their oc- currence in large numbers ; fortunately only a small portion of the pupaa succeed in extrica- ting themselves from their cases ; thousands of them perish by drowning, and are devoured by fish, reptiles, and aquatic insects ; the per- fect gnats supply food for carnivorous insects, the great tribe of fly-catching birds, and the bats. The family of tipuladce are also called gnats; these are often seen performing their aerial dances during the summer, and in shel- tered places even in mild days in winter, pre- ferring the decline of day ; these dancing com- panies are said always to consist exclusively of males; any attempt to intrude upon their sportive circles shows their quickness of vision and of motion, as the whole company is at once removed to a distance. These gnats some- times crowd into houses in immense numbers. GNEISENAU, August, count, a Prussian general, born at Schilda, Oct. 28, 1760, died in Posen, Aug. 24, 1831. He served in the Austrian army, and in that of the margrave of Anspach- Baireuth, with whose troops he served in America under the English, shortly before the close of the revolutionary war. He became captain in the Prussian army in 1789, and after the battle of Jena was appointed commander of the fortress of Colberg (1807), and held the place till the peace of Tilsit. The resentment of Napoleon caused hia dismissal (1809), but he was sent on secret missions to various courts. Afterward he was attached to Bliicher's army as quartermaster general, and as chief of the staff. (See BUTCHER.) He took a leading part in the Silesian campaign of 1813, and after the battle of Leipsic was made lieutenant general. He rendered important services during the cam- paign of 1814 in France, and is said to have advised the march to Paris. After the peace he was made count and general, and received a large estate. After the return of Napoleon from Elba he again served with Blucher, and effected a skilful retreat from Ligny (June 16), enabling the Prussians to reappear at Waterloo (on the 18th), and to decide the fate of the campaign. He now took part in the negotia- tions for peace, was made commander of the Rhenish corps, and accompanied Blucher to England. Disappointed in his expectation of constitutional liberty, he tendered his resigna- tion. In 1818 he was appointed governor of Berlin, and in 1825 field marshal; and in 1831, during the Polish insurrection, he commanded