82 INSECTS AND 
-~ Whence comes, then, all the grace and perfect freedom 
of action seen in the vivacious motions of the Ichneumon 
fly and Butterfly? It lies in the fact that the whole outer 
crust is subdivided into portions which are finely hinged 
together by a tough membrane, forming points of attach- 
ment to thousands of little muscular fibres within, and 
thus giving the otherwise rigid crust a surprising degree 
of flexibility. 
The three pair of legs are inserted at the lower edge of 
the side-piece (cpisternum, Fig, 6, £s), as seen in the fig- 
ure, and the wings grow out between the upper side piece, 
(Fig. 6, £m ) and the tergum (Fig. 6,7). The body 
of all known insects consists normally of twenty of 
these cylindrical rings, each of which is theoretically sub- | 
divided in the manner we have shown ; but towards each _ 
extremity of the body, as in the rings composing the head 
and tail, but a part of the ring is developed, since the 
remaining portions have, during the development of the 
animal, either while still in the egg, or during its growth 
afterwards, become absorbed, and jive consequently disap- 
appeared. In the head of all insects there are, as a rule, 
seven such rings, in the thorax three, and in the hind 
body, or abdomen, at least ten, and perhaps eleven, ele- 
mental segments. Counting, in addition to the 
number of pieces which compose the trunk, the numerous 
joints of the legs, and those of the antennæ, which ap- 
in the Cockroach to nearly a hundred in number, 
A idea of the exceeding complexity of t 
crust. Thus w pripite entomology has to 
sion 
att 
Arran 
