356 
IKSECTA. 
ORDER III. 
PARASITA * 
I’lie 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 moveable appendages. Their organs of 
vision consist of but four or two simple eyes ; a great portion of 
their mouth is internal, exhibiting externally either a snout or jiro- 
jecting mammilla containing a retractile sucker, or two membranous 
and approximated lips with two hooked mandibles. According to 
Linnaeus, they form but one genus, that of 
Pediculu.s, Lin. 
Their body is flattened, nearly diaphanous, and divided into twelve 
or eleven distinct segments, three of which belong to the trunk, each 
})earing one pair of legs. The first of these segments frequently 
forms a sort of thorax. The stigmata are very distinct. The 
antennae 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 
nails, 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 body 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 
facilitate their increase to an astonishing degree in the P. humanus, 
producing in Man what has been termed the mo7'bm pedicidosus, 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 
mammilla situated at the anterior extremity of the head, in the form 
of a snout, containing a sucker Avhen at rest. Tlieir tarsi are com- 
posed of a joint almost equal in size to the tibia, terminated by a very 
stout nail, folding over a projection, and with this point fulfilling the 
function of a forceps. Those which I have examined jn’esented but 
two simple eyes, one on each side. 
* Pantsila, Lat. — Anoplura, Leach. 
