308 ZOOLOGY. 



'thoracic appendages are for walking, and the spinnerets 

 of the spider, as well as the sting or ovipositor of many- 

 insects, are subservient in part to the continuance of the 

 species. 



Of the winged insects there are two types : first, those in 

 which the jaws and maxilla are free, adapted for biting, as 

 in the locust or grasshopper, and, second, those in which 

 the jaws and maxillae are more or less modified to suck or 

 lap up liquid food, as in the butterfly, bee, and bug. 



Nearly all insects undergo a metamorphosis, the young 

 being called a larva (caterpillar, grub, maggot) ; the larva 

 transforms into a pupa (chrysalis), and the pupa into the 

 adult (imago). 



In order to obtain a knowledge of the structure, external 

 and internal, of insects, the student should make a careful 

 study of the anatomy of a locust or grasshopper with the aid 

 of the following description ; and afterward rear from the 

 egg a caterpillar and watch the different steps in its metamor- 

 phosis into a pupa and adult. The knowledge thus acquired 

 will be worth more to the student than a volume of descrip- 

 tions. 



On making a superficial examination of the locust {Galop- 

 tenus fermir-rubrum, or C. spretus), its body will be seen to 

 consist of an external crust, or thick, hard integument, pro- 

 tecting the soft parts or viscera within. This integument 

 is at intervals segmented or jointed, the segments more or 

 less like rings, which, in turn, are subdivided into pieces. 

 These segments are most simple and easily comprehended 

 in the abdomen or hind-body, which is composed of ten of 

 them. The body consists of seventeen of these segments, 

 variously modified and more or less imperfect and diflficult 

 to make out, especially at each extremity of the body — 

 i.e., in the head and at the end of the abdomen. These 

 seventeen segments, moreover, are grouped into three re- 

 gions, four composing the head, three the thorax, and ten 

 the hind-body, or abdomen. On examining the abdomen, 

 it will be found that the rings are quite perfect, and that 

 each segment may be divided into an upper (tergal), a lateral 

 (pleural), and an under (sternal) portion, or arc (Fig. 273, A). 



