JAWS OF INSECTS. 123 



dry leaves, which are their natural food.* In 

 most cases, indeed, we are, in like manner, 

 enabled, from a simple inspection of the shape 

 of the teeth, to form tolerably accurate ideas of 

 the kind of food on which the insect naturally 

 subsists, t ^ 



Above, or rather in front of the mandibles, is 

 situated the lahrum, or upper lip (u). It is 

 usually of a hard or horny texture, and admits 

 of some degree of motion ; but its form and 

 direction are exceedingly various in different 

 tribes of insects. The lower pair of jaws (j), or 

 maxillce, as they have been termed, are behind 

 the mandibles, and between them is situated the 

 labium, or lower lip (l), which closes the mouth 

 below, as the lahrum does above. In the grass- 

 hopper, each maxilla consists of an outer and 

 an inner plate (o and i). The jaws of insects 

 are confined, by their articulations with the 

 head, to motions in a horizontal plane only, so 

 that they open and close by lateral movements, 

 and not upwards and downwards, as is the case 

 with the jaws of vertebrated animals. The 

 maxillae are, in most cases, employed principally 

 for holding the substances on which the dividing 

 or grinding apparatus of the mandibles is exerted. 



* Knoch, quoted by Kirby. 



t See a memoir by Marcel des Serres, in the Annales du 

 Museum d'Hist. Nat. xiv. 56. 



