HUMAN PEDICULI 



327 



may first note its structural peculiarities. It is a flattish, 

 semi-transparent insect, of a pale ashy-grey colour, with 

 a comparatively small 

 head and a very large 

 body. The head, which 

 is narrowed in front and 

 behind, carries a pair of 

 short, five-jointed an- 

 tennae, a pair of simple, 

 rounded, unfaceted 

 eyes, and the mouth 

 organs, of which more 

 presently. Behind it 

 merges into the thorax, 

 which again is not de- 

 finitely marked off from 

 the abdomen, but the 

 three pairs of legs show 

 how far its three seg- 

 ments extend. The 

 legs succeed one an- 

 other without interval, 

 and the first pair are 

 placed immediately behind the head. No wings of any 

 kind are ever developed, nor is any trace of such organs 

 perceptible; hence some naturalists have questioned 

 whether the lice should be included amongst insects at 

 all. Not only is the thorax considerably broader than 

 the head, but this increasing breadth is continued into 

 the abdomen, so that the widest part of the insect is 

 about half-way down the body. The margins of the 

 abdomen show a scalloped edge, there being a series of 

 indentations where the segments adjoin. On each of 

 these rounded projections is placed a small circular 



FIG. no. Head-Louse (Pediculus capitis). 

 Female, viewed from beneath. Magnified 

 22 diameters. 



