FLEA (AS. flea, Icel. fib, OHG. 116h, Ger. Flog; connected with 0110. fliohan, Ger. fliehen, to flee, AS. //eon, Icel. mu. Goth. pliuhan). One of the small wingless insects now commonly re garded as constituting a distinct order, Siphonap tera, containing a single family, Pnlicidm. All the species are very similar to the common Euro pean flea (Pulex irritans). which is plentiful in most parts of the world, and lives by sucking the blood of man and of certain quadrupeds and birds. It abounds particularly in the nests of poultry, pigeons, and swallows, and wherever dust accumulates in the chinks of floors, etc.; and it is to he found also plentifully in beds wherever cleanliness is neglected. The abundance of fleas in some hot, sandy countries is an intolerable nuisance to both travelers and residents. The female is rather larger and stronger than the male, but the sexes are otherwise very similar. The head is small, very compressed, rminded above, and has on each side a small round eye. The mouth has two lancet-like mandibles, the maxil In being represented by two conical scales, the mandibles and the maxilla forming a auctorial beak, with a slender. bristle-like tongue, the whole inclosed between two three-jointed plates. The thorax consists of three segments, the second and third of which bear a scale on each side, regarded as rudimentary wings. There is no marked division between the thorax and the abdomen, which consists of nine segments, much larger than those of the thorax, but much compressed.
The whole body is covered with a tough integu ment. The activity of the flea, its power of leaping, and its extraordinary strength are well known. Its strength has been sometimes applied to the drawing of miniature carriages, cannon, etc. Fleas undergo a complete metamorphosis. The female lays about a dozen white eggs, slightly viscous. The larva is long and slender, at first white, afterwards reddish, and destitute of feet, It subsists upon animal particles in dust and upon the loosened particles of skin caught among an animal's hairs. W'hen about to ehange into a pupa it ineloses itself in a little silk cocoon, from which emerges the perfect. flea. Cleanliness and careful attention are the prin cipal means of keeping beds and houses free of fleas; but where these are found insufficient a free use of kerosene is recommended. The com mon flea of households in the United States is that of the cat and dog (Pulex serraticeps). The flea prevalent upon human beings in the Old World (Pulex irrilans) is rarely seen in America. Squirrels, foxes, rats, and some other animals have separate species, of which in all about 100 are known, a third of which are American. Fleas have been accused of spreading disease, Grassi alleging that the cat-and-dog flea is an intermediate host for tapeworms; and cer tain others carry the bubonic plague. See CHIGOE.