STATES OF INSECTS. (Larva.) 211 
tain themselves in a horizontal position. But these lar- 
vee act as if they foresaw the assumption of a state in 
which they will be deprived of legs. It is the suspension 
of the forthcoming pupa that is the object in view; and 
though this can be hung by the tail in the same way with 
those of the first class, yet it is plain that it cannot be re- 
tained in a horizontal position, which for some unknown 
reason is essential to it, without some support to its an- 
terior extremity. It is necessary for the larva, therefore, 
not only to fix its posterior legs amongst a collection of 
silken fibres, but to spin a gzrth of the same material 
round its body. ‘This girth, though apparently of a sin- 
gle thread, will be found on examination to be composed 
of several, often as many as fifty or sixty; and is fastened 
on each side of the body of the larva about the middle, 
to the surface under which it is placed. Three different 
modes of fixing these girths are adopted by the caterpil- 
lars of different butterflies. Some, as those of the com- 
mon cabbage-butterfly (Pontia Brassica), which have 
remarkably pliable bodies, bend them almost double on 
one side, then fix the thread and carry it over to the 
other in the same position, repeating this operation as 
often as is necessary. Others, as that of Polyommatus 
Argus and many more of the Papiliones Rurales and Ur- 
bicole, which have a short and more rigid body, after 
having bent the head on one side so as to fix one end of 
the thread, bring themselves into a straight position, and, 
by a manceuvre not easily described, contrive to intro- 
duce the head under the thread, which they then bend 
themselves to fasten on the other side, pushing it to its 
proper situation by the successive tension and contrac- 
tion of their segments. But the most curious mode, 
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