MORSE: ORTHOPTERA OF NEW ENGLAND. 
215 
The Insect Body and Skeleton. 
The body of an insect is made up of three general regions: 
head, thorax, and abdomen. These three parts are conspicuous 
in ants, bees, and wasps, but less noticeably distinct in other 
orders of insects. The head bears the eyes, 'feelers' or antennae, 
and mouth-parts. The thorax bears three pairs of legs, and 
typically two pairs of wings. The abdomen forms the remaining 
posterior portion of the body, and at its tip bears appendages of 
variable size and character which are used as sense organs, for 
defence, for securing prey, in mating, or in depositing the eggs. 
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Fig. 2. — Drawing of Locust, side view, showing chief parts. Enlarged. (After Walden.) 
The supporting skeleton of an insect is chiefly external, instead 
of internal as in the higher, backboned animals, occupies the 
place that the skin does in them, and forms the body-wall. It is 
composed largely of a peculiar horn-like substance named chitin, 
which is deposited in variable amounts in different parts of the 
body-wall, forming stiff, somewhat elastic portions (sclerites) 
connected by soft and pliable areas which allow movement. 
Sometimes the sclerites. are immovably joined but their limits 
may usually be distinguished by lines or narrow grooves termed 
sutures. Motion is effected by muscles enclosed within the body- 
wall, extending from one segment to another. 
The ring-like segments of the middle of the abdomen (Fig. 1-3) 
