sively confined to Birds. Their head is usually large, sometimes 

 triangular, and at others forming a semicircle or crescent, and fre- 

 quently presenting angular projections. It sometimes differs, like the 

 antennae, in the two sexes. I have perceived, in several, two simple 

 approximated eyes, on each side of the head. According to the obser- 

 vations of M. Savigny, communicated to me by himself, these animals 

 are provided with jaws, each of which has a very small palpus, hidden 

 by the lower lip, which has also two organs of the same description. 

 They have moreover a kind of tongue. 



M. Leclerc de Laval informs me that he has found parcels of fea- 

 thers in their stomach — he thinks that they constitute their only food. 

 De Geer, however, assures us that he has found the Pediculus of the 

 Fringilla ccelebs filled Avith recently imbibed blood. It is well known 

 that these Insects survive but a short time on dead birds. When 

 thus situated, they are observed to wander over their plumes with 

 much anxiety, those of the head and the vicinity of the beak espe- 

 cially. 



Redi has also represented a great number of species of this sub- 

 genus. 



The mouth of some is situated near the anterior extremity of the 

 head. The antennse are very small, inserted laterally, and at a dis- 

 tance from the eyes*. 



In the others, the mouth is nearly central ; the antennae are placed 

 close to the eyes, and their length about equals half that of the 

 head f . 



The celebrated professor Nitzsch has profoundedly 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 MaUopharja. Tavo genera of this 

 division approach tlie preceding ones in the circumstances 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, &c. 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 



* Pediculus sternte hirundinis, L, ; De Geer, Insect., VII, iv, 12 ; — Ped. corvicora- 

 cis, L. ; De Geer, lb., ii ; — Ricinus fringillce, De Geer, lb., 5, 6, 7 ; — Ped- tinnun- 

 culi, Panz., lb., xvii. 



f Ricinus gallince, De Geer, lb., 15 — on the Cock, Partridge, and Pheasant; — 

 R. emberizce, De Geer, lb., 9 ; — R. mcrgi, De Geer, lb., 13, 14 ; — R. canis, De Geer, 

 lb., 16; — Pediculus pavonis, Panz., lb. xix ; Lat., Hist. Nat. des Fourm., 389, xii, 

 5. See also Panz., lb., pi. xxv — xxiv. His Pediculus ardea, XVIII, appears to be 

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



