214 
SYSTEMATIC ARRANGEMENT. 
in Blatta which may be regarded as representing 
them. 
The clypeu 8 or shield is always distinct among the 
Orthoptera, (Plate VI. fig. 2, c .) In several families 
of this order, “ the suture, uniting the shield with 
the upper part of the skull, is membranaceous ; hence 
the lip and shield move simultaneously with the 
mandibles in mastication. This is a departure from 
the general law of nature, and its occurrence is well 
worth remarking ; as the motion of the shield might 
induce an observer to suppose it the lip, which would 
consequently become a new and supernumerary ele- 
mentary part.” * 
Of the three segments composing the thorax, the 
prothorax is often very much developed, to such a 
degree indeed, that in a particular group of the old 
genus Gryllus it sometimes exceeds in size all the 
rest of the insect. The mesothorax is very incon- 
spicuous in this order, for the reason, that the fore- 
wings do not take a very important share in flight, and 
the part which supports them therefore admits of 
diminution. It is scarcely observable, indeed, when 
the wings are closed, except in certain species of the 
Mantis tribe. The metatliorax, which is seldom so 
much developed as the preceding sections in the 
generality of insects, here acquires considerable pro- 
minence, and in certain Phasmse seems to have at- 
tained its maximum. 
The metamorphosis of orthopterous insects, is what 
* External Anat. of Ins. Ent. Mag . vol. //. 65. 
