6 FIELD ZOOLOGY. 



wings and the legs. The insect's body wall is rendered 

 flexible by the fact that between any two segments there 

 is a non-chitinized area; these chitinized areas with the 

 non-chitinized areas between constitute sclerites, and the 

 degree of flexibility depends upon the depth of the infold- 

 ing of the soft, non-hardened cuticle between any two 

 sclerites. 



Looking the grasshopper straight in the face, there 

 will be seen a sclerite coming down from the upper part of 

 the face and nearly covering the mandibles, the maxillae, 

 and the other mouth parts. This is the labrum or upper 

 lip; it is hardly to be called an appendage of the mouth, 

 but is rather a fold of the cuticle covering the mouth. The 

 mandibles usually consist, as in the grasshopper just 

 studied, of one segment. The labium usually forms one 

 single piece, but in many of the insects it is modified 

 into several pieces, as in the flies, the bugs, and the 

 butterflies. In certain insects, some of the other mouth 

 parts may be reduced to mere rudiments or may be lost 

 altogether, not developed because functionless. 



At the side of the grasshopper's head may be seen the 

 large compound eyes. With a hand lens these will be 

 seen to be composed of a large number of very small flat 

 faces, instead of forming one smooth, globular surface 

 like the human eyeball. Just inside the margin of each 

 compound eye may be found two of the simple eyes, and 

 lower down in a groove of the grasshopper's face is the 

 third simple eye. These look like tiny beads. A house- 

 fly has three of these simple eyes, but they are set in a 

 much smaller triangle between the two compound eyes 

 and more nearly on top of the head. 



