152 CLASS INSECTA. ^^ 



A celebrated German naturalist, Dr. Nitzsch, professor 

 at Halle, has made a very profound study of the organi- 

 zation, both internal and external of these animals, as is 

 proved by his memoir on the epizoic insects, inserted in the 

 entomological magazine of M. Geunar. The genus pedi- 

 culus properly so called, or that whose species are provided 

 with a sucker, is ranged by him with the epizoic hemiptera. 

 The ricini of Degeer, and others, or the nirmi of Hermann, 

 that is, the species provided with mandibles and jaws, are 

 referred to the order orthoptera, and designated, collectively, 

 by the name of mallophagi. Two genera of this division 

 approach the preceding, inasmuch as these animals also 

 live on the mammifera : such are the trichodectes and gyro- 

 pus. In the first, the maxillary palpi are wanting, or indis- 

 tinct, and the antennae are filiform and of three articulations. 

 Their species are found on the dog, the badger, the weasel, 

 the ferret, &c. In the second, the maxillary palpi are appa- 

 rent, the antennas are thicker towards the end, and have four 

 articulations ; its mandibles have no teeth, and the labial 

 palpi are nullified, and the four posterior tarsi have but a 

 single crotchet at the end. These latter characters distin- 

 guish it from another genus, having maxillary palpi visible, 

 antenna with four articulations, and thicker at the end, and 

 the anterior mouth, as of the liotheum. Here the mandi- 

 bles are bidenticulated, the labial palpi are distinct, and all 

 the tarsi are terminated by two crotchets ; the species are 

 found on divers birds, whereas the gyropi live on the qua- 

 drupeds vulgarly called guinea-pigs. A fourth and last 

 genus, that is that of philopterus, whose species are exclu- 

 sively proper to birds. The antennae have five articulations, 

 the third of which, in the males, often presents a branch form- 

 ing a pincers with the first ; these organs are filiform. The 

 maxillary palpi are invisible. The tarsi have two crotchets 

 at their extremity, but not divergent like those of the liothea. 

 Here, moreover, the males have six testicles, three on each 



