STRUCTURE OF INSECTS. 61 



Fig. 48, and may stand as a type of all the other beetles, 

 since they do not differ in Fig. 48. 



their structures. This spe- 

 cimen is of the natural 

 size, but the sections are 

 somewhat magnified, that 

 the smaller parts may be 

 more distinctly seen. 



166. The head c, Fig. 

 49, contains the principal 

 enlargement of the ner- 

 vous system, or the brain, 

 the scull or cranium being 

 usually the hardest part of 

 the insect. To the head 

 are attached the antennae, 

 and instruments of masti- 

 cation. The latter are much more complicated in insects 

 than in larger animals. Those which divide their food, 

 have a double set of jaws, called mandibles and maxilla, 

 beside which, there are four other moveable pieces 

 called palpi, and labial palpi. The mandibles, or upper 

 jaws, m, cut the food ; the lower, or proper jaws, j 9 mas- 

 ticate it ; the palpi, p, and the labial palpi, /, appear to 

 be instruments of sense by which the insect judges of 

 the quality of its food. The motions of all these parts, 

 are horizontal, and not vertical as with us, and other ani- 

 mals having incumbent maxillae. To obtain an idea of the 

 motions and uses of these parts, it is only necessary to 

 watch an insect for a few moments while feeding. 

 Fig. 49. 



167. The trunk, or thorax, is composed of three parts, 



What are the jaws of insects called ? What other pieces belong to the 

 mouths of insects ? What are the uses of the mandibles and proper jaws ? 

 What are the uses of the palpi ? 



6 



