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Show 326 INSECTA. point. The two anterior legs are long, slender, folded in two, and w}len contracted, almost at a right angle with the body; they are ter. minated by a very short, strongly compressed tarsus, the inferior surface of which, in the males, is furnished with a fine compact brush. The four others are broad and extremely thin, the joints of ' their tarsi forming little leaflets arranged like a flounce. The Gyrini are usually small, or of a moderate size. They are to be found from the very beginning of spring until the end of autumn, on the surface of stagnant waters, and even on that of the Ocean, where, frequently collected in troops, they appear like brilliant points, swimming and wheeling with great agility in all sorts of curves, and in every direction, whence the name of Puce aquatique and Tourniquet given to them by authors. Sometimes t.hey remain motionless, but the instant any one approaches, they escape by swimming, and dive with great celerity. Their four last legs serve them as oars, and the two before for seizing their prey. Placed 00 water, the superior surface of their body is always dry, and when they dive, a little bubble of air, resembling a silvery globule, re. mains fixed to its posterior extremity. When seized, a lacteous fluid oozes from their body which spreads over it, and which, perhaps, produces that disagreeable and penetrating odour they then diffuse, and which remains attached to the fingers for a long time. They copulate on the surface of the water. Sometimes they remain at the bottom clinging to plants: there, also, it is probable they secrete themselves to pass the winter(l). G. natator, L.; Panz., Faun. Insect. Germ. III, 5; De Gcer, Insect., IV, xiii, 4, 19. Three lines in length; oval, glabrous, very glossy; bronze-black above; black beneath; legs fulvous; scutel triangular, very pointed, somewhat longer than wide; elytra rounded at the extremity, and marked with small im· pressed puncta in regular and longitudinal lines. The female lays her eggs on aquatic plants. They are very small, and form little yellowish white cylinders. The bodyof the larva is long, tapering, linear, and consists of thirteen annuli, each of the three first bearing a pair of legs. The head is large, of an elongated oval shape, and much flattened, pre· senting the same parts as that of the larva of a Dytiscus; but ( 1) M. Leon Dufour, Ann. des Sc. Nat., Oct. 1824, has published some ana· tomical observations on these Insects. The small intestine is remarkable for ill length. The ccecum is not lateral as in Dytiscus. The genital organs of the males differ from those of the other Carnivora. COLEOPTERA. 327 here the fourth and seven following annuli are furnished on each side with a conical, membranous, flexible filament with bearded edges. The twelfth ring has four similar, but much longer ont>s, directed more postet·iorly. Two very slender trachere traverse the whole length of the body, and receive an air vessel from each filament. The last ring is very small, and is terminated by four long and parallel hooks. This larva inhabits the water, from which it issues in the beginning of August to become a chrysalis. It encloses itself in a little oval cocoon, pointed at the ends, formed of a material drawn from its body resembling grey paper, which it fixes to the reeds. Very common in Europe(l). FAMILY II. BRACHELYTRA. In the second family of the Pentamerous Coleoptera we find but one pal pus to the maxillre, or four in all; the antenn:e, sometimes of equal thickness, and at others slightly enlarged at the end, are usually composed of lenticular or graniform joints; the elytra are much shorter than the body, which is narrow and elongated, and the coxre of the two anterior legs are very large ; near the anus are two vesicles which the animal protrudes at will. These Coleoptera compose the genus ST APHYLINus, Lin. The Staphylini have been considered as forming the passage from the Coieoptet·a to the Forficulre, the first genus of the following order. (1) For the other species see Oliv., Col. liT, No. 41, and Scbamh., Synon. Insect., II, No. 55. The Gyr. minutua and bicolor, Fab., are also found in the vicinity of Paris. The largest of the species, all of which at·e foreign to Europe, have no apparent scutel and but four pal pi. M. Mac.Leay, Jun.-Annul. Javan. I, p. 30-forms a particular genus, DINEu· TEs, with those in which the labrum is not ciliate, the palpi nre clavate, the anterio. r legs the length of the body, and the termination of the antennce is partly pomted. He quotes but a single species, the D. politw. Add American species of Gyri nus, the Gyr. americanus, emarginatus, anali1 and limbatm. .IJ.m. Ed. |
