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 maxille are free, adapted for biting, as 
in the locust or grasshopper, and, second, those in which 
the jaws and maxille 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 Jarva (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 (Calop- 
tenus femur-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 difficult 
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 are (Fig. 273, A). 
