THE BRITISH WOODLICE. 3 
terminal part, or flagellum, and a basal part, the peduncle (fig. 3). 
The number of joints in these structures, which varies in different 
genera and species, forms a useful classificatory character, and 
Dicker Ko FLAGELLUM 
Jobe on WY / 
FIG, 3.—THE SECOND ANTENNA. 
(Ontscus asellus.) 
the relative length of the component parts is of considerable 
value in distinguishing species. 
There are four pairs of mouth appendages—-namely the jaws 
FIG. 4.—THE UNDERSIDE OF THE HEAD. 
(Oniscus asellus.) 
or mandibles (fig. 5), the first maxillae (fig. 6), the second maxilla 
(fig. 7), and the maxillipeds (fig. 8). When the head is examined 
from the underside the last of these organs will be seen first, 
covering in the others, 
