8o 



INSECTS. 



consists of an upper and an under lip, and four horny jaws. The 

 upper lip (labruiti) (Figs. 70, 71,0) is a convex horny plate, placed 

 transversely across the upper margin of the cavity in which the 

 jaws are lodged, so that when the mouth is shut, it folds down to 

 meet the under lip (labium) g\ and these two pieces more or less 

 conceal the proper jaws, which are lodged between them. 



The upper pair of jaws (mandibula}, b, 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- 



FIG. 71. MOUTH OF A BEETLE. 



FIG. 72. VARIOUS ANTENNAE. 



animal and vegetable substances ; sometimes they form sharp 

 and pointed fangs, adapted to seize and pierce their victims ; and 

 not unfrequently they constitute a series of grinding surfaces, dis- 

 posed 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 carnivorous 

 beetles their hooked points, more formidable 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 

 weapons of destruction. In the locust tribes these organs are 

 equally efficient agents in cutting and masticating leaves and 

 vegetable matters adapted to their appetites, while in the wasps 



