THE BRITISH WOODLICE. 



41 



A small median plate attached to the front of the head has 

 >een called " the upper lip "(fig. 9), while inside the mouth 



appendages is a little bilobed structure 

 " the lower lip " (fig. 10). 



Before leaving the external features 

 of the head, we must allude to the 

 pair of eyes which are usually present, 

 though never raised on stalks. In 

 the Common Wood-louse (Oniscus 

 asellus, from which all our figures to 

 illustrate structure have been made), 

 as in many other species, the eyes are 

 compound (fig. 4), but in some forms 

 these are simple. 



Each of the seven joints of the 

 thorax bears a pair of walking legs 

 (fig. 1 1), and in the female at the time 

 when the eggs are laid, a pair of 

 plates (fig. 12) arises on segments 

 II. to V. These plates together 



FIG. 5 — THE MANDIBLES. 



(Oniscus asellus.) 



FIG. 6. — THE FIRST MAXILLAE. 



(Oniscus asellus.) 



FIG. 7. — THE SECOND MAXILLAE, 



(Oniscus asellus.) 



FIG. 8.— THE FUSED MAXILLIPEDS. 



(Oniscus asellus.) 



form a brood pouch, in which the eggs are carried (fig. 12) 

 until they are hatched, and in which the young ones remain 

 for some time afterwards. 



