102 
ZOOLOGY, 
steps in its metamorphosis into a pupa and adult. The 
knowledge thus acquired will be worth more to the student 
than a volume of descriptions. 
On making a superficial examination of the locust {Caloptenus 
femur -ruhrum), its body will be seen to consist of an external crust, 
or thick, hard integument, protecting the soft parts within. This 
integument is at intervals segmented or jointed, the segments more 
or less like rings. These segments are most simple and easily compre- 
hended in the abdomen or hind-body, which is composed of ten of 
them. 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. 127, A). 
As these parts are less complicated in the abdomen, we will first 
study this region of the body, and then examine the more complex 
thorax and head. The abdomen is a little over half as long as the 
body, the tergum extending far down on the side and merging into 
the pleurum without any suture or seam. The pleurum is indicated 
by the row of spiracles, which will be noticed further on. The 
sternum forms the ventral side of the abdomen, and meets the 
pleurum on the side of the body. 
In the female (Fig, 127, B), the abdomen tnpers somewhat toward 
the end of the body, to which are appended the two pairs of stout, 
hooked spines, forming the ovipositor (Fig. 127, i>, r, r'). The vent 
is situated above the upper and larger pair, and the external open- 
ing of the oviduct, which is situated between the smaller and lower 
pair of spines, and is bounded on the ventral side by a movable tri- 
angular acute flap, the egg-guide (Fig. 127, eg). 
The thorax, as seen in Fig. 127, consists of three segments, called 
the prothorax, mesothorax, and metathorax, or fore, middle, and 
hind thoracic rings. They each b( ar a pair of legs, and the two 
hinder each a pair of wings. The upper portion of the middle and 
hind segments, owing to the presence of wings and the necessity of 
freedom of movement to the muscles of flight, are divided or differ- 
entiated into two pieces, the scutffm and scutellum* (Fig. 127), the 
former the larger, extending across the back, and the scutellum a 
smaller, central, shield-like piece. The pronotum, or what is usually 
in the bookc called the prothorax, represents either the scutum or 
* There are in many insects, as in many Lepidopfera and Hymenop- 
tera and the Neiiroptera, four tergal pieces, i.e., praescutum, scutum, 
scutellum, and postscutellum, the first and fourth pieces being usu- 
ally very small and often obsolete. 
