258 MANUAL OF ZOOLOGY. 



Order I. Anoplura. — Minute Aptera, in which the mouth 

 is formed for suction; and there are two simple eyes, or 

 none. 



This order comprises insects which are commonly parasitic 

 upon man and other animals, and are known as Lice (Pediculi). 

 The common Louse is furnished with a simple eye, or ocellus, 

 on each side of a distinctly differentiated head, the under sur- 

 face of which bears a suctorial mouth. There is little distinc- 

 tion between the thorax and abdomen, but the segments of 

 the former carry three pairs of legs. The legs are short, with 

 short claws or with two opposing hooks, affording a very firm 

 hold. The body is flattened and nearly transparent, composed 

 of eleven or twelve distinct segments, and showing the stig- 

 mata very plainly. The young pass through no metamorphosis, 

 and their multiplication is extremely rapid. Most, if not all, 

 Mammals are infested by Lice, each having generally its own 

 peculiar species, and sometimes having two or three. Three 

 species are said to belong to Man — viz., Pediculus humanus, 

 P. capitis, and P. pubis. 



Order II. Mallophaga. — Minute Aptera, in which the 

 mouth is formed for biting, and is furnished with mandibles 

 and maxillae. 



The members of this order are commonly known as " Bird- 

 lice," being parasitic, sometimes upon Mammals, but mostly 

 upon Birds. They strongly resemble the Pediculi, but the 

 mouth is formed for biting, to suit their mode of life— since 

 they do not live upon the juices of their hosts, but upon the 

 more delicate tegumentary appendages. 



Order III. Thvsanura. — Apterous insects, usually with a 

 masticatory mouth, and having the extremity of the abdomen 

 furnished with locomotive appendages. 



The most fainiliar members of this order are the Podurce, or 

 " Spring-tails," which are characterised by the possession of a- 

 forked caudal appendage, by the extension of which consider- 

 able leaps can be effected. In the nearly allied Lepismce, loco- 

 motion is assisted by caudal bristles. In both, the body is 

 covered with hairs or scales, the structure of the latter being 

 often very beautiful. 



Sub-class II. Hemimetabola. — Metamorphosis incomplete; 

 the larva differing from the imago chiefly in the absence of wings, 

 and in size ; pupa usually active, or, if quiescent, capable of move- 

 ment* 



* The Coccidce, amongst the Hemiftera, undergo a complete metamor- 

 phosis. In certain of the Hemiptera and Orthoptera the adult is apterous, 

 and in these cases there cannot be said to be any metamorphosis, since 



