258 INSECTA. 



ORDER III. 



PARASITA(i). 



The Parasita, so called from their parasitical habits, have 

 but six legs, and are apterous, like the Thysanoura; but their 

 abdomen is destitute of articulated and movable appendages. 

 Their organs of vision consist of but four or two simple eyes ; 

 a great portion of their mouth is internal, exhibiting exter- 

 nally either a snout or projecting mammilla containing a re- 

 tractile sucker, or two membranous and approximated lips 

 with two hooked mandibles. According to Linnseus, they 

 form but one genus, that of 



Pediculus, Lin. 



Their body is flattened, nearly diaphanous, and divided into 

 twelve or eleven distinct segments, three of which belong to the 

 trunk, each bearing one pair of legs. The first of these segments 

 frequently forms a sort of thorax. The stigmata are very distinct. 

 The antennse are short, equal, composed of five joints, and frequently 

 inserted in a notch. There are one or two small ocelli on each side 

 of the head. The legs are short, and terminated by a very stout 

 nail, or two opposing hooks, which enable these animals to cling 

 with great facility to the hairs of Quadrupeds, or to the feathers of 

 Birds, whose blood they suck, and on whose bodies they propagate 

 and pass their lives. They attach their ova to these cutaneous ap- 

 pendages. They multiply excessively, and one generation succeeds 

 to another with great rapidity. Particular and unknown causes faci- 

 litate their increase to an astonishing degree in the P. humanus, 

 producing in Man what has been termed the morbus pediculosus, and 

 even in children. These Insects always live on the same Quadrupeds 

 and on the same Birds, or at least on animals of these classes, which 

 have analogous characters and habits. Two species frequently live 

 on the same Bird. Their gait in general is very slow. 

 Some of them Pediculea. Leach such as the 



Pediculus, Deg., 

 Or true Lice, have a mouth consisting of a very small tubular mam- 



(1) Parasita, Eat. Jlnoplura, Leach. 



