106 



INSECTS. 



is shut, it folds down to meet tlie under lip (labium) g ; 

 and these two pieces more or less conceal the pro})er 

 jaws which are lodged between them. 



The upper pair of jaws {incmdibulm), h, are hard 

 and powerful shears, placed immediately beneath the 

 upper lip, and so jointed to the cheeks that they 

 move horizontally, opening and shutting like a pair 

 of scissors. Their concave edge is armed with strong 

 denticulations of various kinds, sometimes furnished 

 with cutting edges, that, like sharp shears, will clip 

 and divide the hardest animal and vegetable sub- 

 stances ; sometimes they form sharp and pointed 

 fangs, adapted to seize and pierce their victims ; 

 and not unfrequently they constitute a series of 

 grinding surfaces, disposed like the molar teeth of 

 quadrupeds, to triturate and bruise the materials 

 used as food. The variety of uses to which these 

 mandibles can be turned is indeed amazing. In the 



Fig. 71.— JiorxH ok a beetle. 



carnivorous beetles their hooked points, more formi- 

 dable than the teeth of the tiger, penetrate with ease 

 the mailed covering of their stoutest congeners, and 

 in the dragon-fly they are scarcely less formidable 



