490 



INSECTA. 



or conical, the base of which is covered by two scales. These characters exclusively distin- 

 guish it from all other insects, including the Hemiptera, with which it was ranged by Fabricius. 

 The Suctoria, moreover, undergo real metamorphoses, analogous to those of many two-winged 

 insects, as the Tipulidae. 



This order is composed of the single genus of Fleas, — 



Pulex, Linn. 

 The body is oval, compressed, inclosed in a tough skin, and divided into twelve segments, of which 

 three compose the trunk, which is short, and the others the abdomen. The head is small, very com- 

 pressed, rounded above, truncate, and ciliated in front. It has, on each side, a small, round eye, be- 

 hind which is a cavity, in which is placed a small, moveable body, furnished with minute spines. At 

 the anterior edge, near the base of the beak, are situated the pieces which have been considered as the 

 antenna?, which are scarcely so long as the head, and are composed of four nearly cylindrical joints. 

 The sheath of the beak is composed of three joints. The abdomen is very large, and each of its seg- 

 ments is divided in two, being formed of two plates, one superior and the other inferior. The legs are 

 robust, particularly the posterior, fitted for leaping, spinose, with the coxae and thighs very large, and 

 the tarsi composed of five joints, the last terminated by two long nails. The two fore-legs are inserted 

 almost beneath the head, and the beak is placed between them. 



The female lays about a dozen white, slightly viscid eggs, whence emerge small larvae, destitute of 

 legs, very much elongated, resembling minute worms, very active, coiling themselves up in a circle or 

 spire, serpenting in their progress, at first white and afterwards reddish. Their body is composed of a 

 scaly head, without eyes, bearing two very minute antennae and thirteen segments, with small tufts of 

 hairs and a pair of little hooks at the tip of the last. The mouth exhibits a few small, moveable parts, 

 of which the larvae make use in pushing themselves forwards. After living about twelve days under 

 this form, these larvae inclose themselves in a small silken cocoon, where they become pupae, and from 

 whence they make their escape in the perfect state, at the expiration of a similar period. 



i__j Every one knows the common Flea (Pulex irritans, Linn.), which 



feeds on the blood of Man, the Dog, and Cat. Its larva lives amongst 

 dirt, and beneath the nails of filthy persons; also in the nests of birds, 

 such as Pigeons, attaching itself to the necks of the young, and gorging 

 itself till it becomes red. Well figured by Dumeril (Consid. Generates 

 sur la Classe des Insectcs.) — Pulex penetrans, Linn., probably forms a 

 peculiar genus. Its beak is of the length of the body. It is known in 

 America under the name of the Chigoe [or Jigger]. It introduces itself 

 beneath the nails of the feet and the skin of the heel, where it soon ac- 

 quires the size of a small pea, by the quick growth of the eggs, which 

 it bears in a large membranous bag beneath the abdomen, the nume- 

 rous family from which occasions, by remaining in the wound, an 

 ulcer, very difficult to heal, which even sometimes becomes mortal. Frequent washings, and rubbing the feet 

 with fresh tobacco leaves, or those of other bitter plants, are preventives against its attacks. The negroes [or 

 more commonly the negresses] are in the habit of extracting the insect, with great skill, from its lodgement. 

 Various quadrupeds and birds nourish Fleas, which appear to differ specifically from the two preceding. 



[The structure of the head and mouth of these insects has been investigated by recent entomo- 

 logists, especially by Curtis, Duges, and myself. The moveable organs noticed above, implanted in a 

 cavity at the back of the sides of the head, are proved to be antennae, varying considerably in form in 

 various species. Their variations have led to the proposal of another genus for certain species, by 

 Mr. Curtis. The two flat pieces noticed by Roesel, are the lancet-like mandibles ; the two conical scales 

 at the base of the mouth are the maxillae, the long antenna-like organs in front of the head being the 

 maxillary palpi ; the third piece, noticed above as described by Kirby, is the slender setiform tongue, 

 and the two articulated plates above described are the labial palpi, arising from a common labium. 

 Thus the mouth is seen to consist of all the essential parts, except an upper lip, which is obsolete in 

 many other tribes. M. Duges has also detected two scales on each side of the meso- and metathorax, 

 which he considers as the real analogues of the two pairs of wings. 



Various species of Fleas have been described by Curtis, Duges, &c. The Chigoe has also been in- 

 visdgated by Duges, Gueriu, and myself, from whence it appears that the large mass of eggs causes 

 the abdomen to become immensely swollen. The mouth is of the ordinary type, but the lower lip is 

 destitute of labial palpi, whence I have proposed for it the generic name of Sarcopsyllus, or Flesh-flea.] 



Fig. 51. — The Flea (Pulex irritans). 



