158 ELEMENTARY ZOOLOGY 



attached, as are also the two pairs of wings. The re- 

 maining segments of the body compose the abdomen. 

 Note the smooth, rather firm and horny character of 



antennae 

 /\ 



auditory organ 

 ocellus I 



head compound eye \ 



-ovipositor 



femur* 

 tibia/ 



tar sal segments 



FIG. 38. The red-legged locust. Mclanoplus femitr rubnim, to show ex- 

 ternal structure. 



the body. This is due to the fact that the skin is every- 

 where covered with a cuticle in which is deposited a 

 horny substance called chitin. The cuticle is not uni- 

 formly firm over the body. At the junction of the body 

 segments in the abdomen, in the neck and between the 

 segments of the legs, in fact, wherever motion is desir- 

 able, the cuticle is flexible, thus making bending of the 

 body-wall possible. Elsewhere, however, it is hard and 

 stiff, serving not only as a protective coat or armor over 

 the body, but also affording firm places for the attachment 

 of muscles. 



Insects (and all other Arthropods) have no * internal 

 skeleton, but, in this firm cuticle, an exoskeleton, 



Although the head is apparently a single segment, it 



* There are in many forms a few internal projections from the exterior 

 cuticle which act as internal skeletal pieces. 



