PARASITA. 261 



The celebrated professor Nitzsch has profoundly studied the in- 

 ternal as well as external organization of these animals, as may be 

 seen by referring to his paper on the Epizoic Insects, in the Magasin 

 der Entomologie of M. Germar. The genus Pediculus, properly so 

 called, or that whose species are provided with a sucker, is arranged 

 by him with the Epizoic Hemiptera. The Ricini of De Geer and 

 others, or the Nirmi of Hermann, Jun., that is to say, the species fur- 

 nished with mandibles and jaws, are referred to the Orthoptera, and 

 collectively designated by the term Mullophaga. Two genera of this 

 division approach the preceding ones in the circumstance of living 

 on the Mammalia — such are Trichodectes and Gyropus. In the 

 first the maxillary palpi are null or indistinct, and the antennae fili- 

 form, and composed of three joints. The species of this genus are 

 found on the Dog, Badger, Sec. In the second the maxillary palpi 

 are apparent, and the antennae, thicker towards the end, consist of 

 four joints. The mandibles have no teeth; there are no labial palpi, 

 and the four posterior tarsi have but a single terminal hook. These 

 last characters distinguish it from another genus, also furnished 

 with visible maxillary palpi, quadriarticulated antennae thicker near 

 the extremity, and an anterior mouth, that of Liotheum. Here the 

 mandibles are bidentate, the labial palpi distinct, and all the tarsi 

 terminated by two hooks. The species are found on various Birds, 

 whereas the Gyropi live on the Guinea-pig. A fourth and last ge- 

 nus, the species of which are exclusively confined to Birds, is that 

 of Philopterus. The antennae consist of five joints, the third of 

 which, in the male, frequently presents a branch that forms a for- 

 ceps with the first; these organs are filiform. The maxillary palpi 

 are invisible. The tarsi have two hooks at their extremity, but they 

 do not diverge like those of the Liothea. Besides this, the males 

 here have six testes, three on each side, and their four biliary ves- 

 sels are thickened near the middle of their length. Those of the 

 Trichodectes and Philopteri do not exhibit this enlargement, and 

 they have but four testes, two on each side. In these two genera 

 there are also ten ovaries, five on each side; in such of the female Lio- 

 thea as this savant could find them, he saw but six, three on each 

 side. He has no positive knowledge of the number of those in the 

 female Gyropi, nor of that of the testes in the males. In all these 

 genera the thorax is bipartite, that is, the prothorax and the meso- 

 thorax compose the apparent trunk, and the third division, or the 



R. emberizx, De Geer, lb., 9; — JR- mergi, De Gear, lb., 13, 14-, — It. canis, De 

 Geer, lb., 16; — Pediculus pavonis, Panz., lb., xix; Lat., Hist. Nat. des Fouim., 

 389, xii, 5. See also Panz., lb., pi. xx — xxiv. His Pediculus ardcse, XVHI, ap- 

 pears to be the same as the Ricin du plongeon, De Geer, IV, 13. 



