64 NATURAL HISTORY OF WASPS. 
which wasps have to do, and the circumstances of 
their daily life, no covering could be devised more 
exactly adapted to their wants than that which they 
possess. It is hard and resisting, yet as sensitive as 
our hard teeth; and, since the perfect insect has no 
means of repairing the injuries which it may receive, 
it is made as little liable to injury as possible. It is 
rigid or flexible in different parts, according to the 
uses of those parts, but, still with due regard to the 
life which the wasp leads, this flexibility is not 
gained by weakening the defensive armour more 
than can be helped. Many insects have unguarded 
points, but the wasp carries a complete coat of mail. 
In the structure of her limbs the wasp displays, in 
common with all other insects, the object of the 
skeleton being placed outside. In no other way 
could the same amount of material have been dis- 
posed to equal advantage according to mechanical 
laws. A larger surface is thus obtaimed for the 
attachment of the muscles and for the articulations. ~ 
And, by the skeleton answering the double purpose 
of skin and bone, all the weight of the former is 
saved. 
The three great divisions of the msect body, 
which give this class of animals their peculiar form 
and their name, are singularly distinct in wasps ; the 
head, thorax, and abdomen are readily separable 
from each other. It will be more convenient to 
follow these natural divisions, and to examine the 
chief organs contained within, or connected with 
each of them successively, than to study each system 
of organs separately, as a whole. 
