PULEX, in natural history, the ,flea, a genus of insects of the order aptera. Ge neric character : mouth without jaws or feelers, with a long inflected proboscis, covered at the base with two ovate la mince; the sheath two-valved, five-joint ed, and concealing a single bristle ; lip rounded and fringed with reflected prie kles ; antenna projecting, moniliforni; two eyes ; abdomen compressed ; six legs formed for leaping. There ate two spe cies, viz. P. irritans, the common flea : and P. penetrans, or chigger.
The common flea is remarkable for un dergoing the several changes experi enced by the greater part of the insect race of other tribes, being produced from an egg in the form of a minute larva, which changes to a chrysalis, in order to give birth to the perfect animal. The egg is small, oval, and white, and from this in a few days is hatched the larva, which is destitute of feet, beset with hairs, and furnished at the head with a pair of short antenna, and at the tail with a pair of slightly curved forks. The
larva in about ten days arrive at their full growth, when they cease to feed, and casting their skin, change into the state of a chrysalis, which is of a white colour, and of an oval shape, with a slightly pointed extremity, and exhibits the im mature limbs of the included insect. Af ter remaining in the chrysalis state about a fortnight, the complete insect emerges, in its perfect form. The singularity most worthy of notice in the flea is the situa tion of the first pair of legs, which are placed beneath the head. The eyes are large, round, and blacks. the male is smaller than the female, with the back rather sinking than convex, as it always is in the female.
P. penetrans, or chigger, is a native of South America and the West India islands : it is said to be exceedingly troublesome in the sugar colonies, pene trating into the skin of the inhabitants, ' where it lodges its eggs, and causes ma lignant, and•sometimes fatal ulcers.