272 STATES OF INSECTS. (Pupa.) 
perfect insect in pupz of all the other orders. This is 
sometimes a work of difficulty, but ordinarily it is effected 
with ease. 
Incomplete and semicomplete pupee undergo nearly the 
same process, save that in them the body is not swathed 
up in a common case; and therefore they have only to 
liberate themselves from the partial cases that envelop the 
several parts of their body. 
In coarctate pup, as those of Muscidae, Syrphide, 
Gstride, &c., the process is different. ‘Their outer-case 
is ordinarily more rigid and destitute of the sutures, 
which in the former tribes so easily yield to a slight effort. 
Yet in these, at the anterior end under which the head of 
the fly lies, and from which it always issues, there is 
commonly a sort of lid, joined by a very indistinct suture 
to the rest, which can be pushed off, leaving a sufficient 
opening for the egress of the insect. In the pupz of 
many of this tribe this lid is composed of two semicir- 
cular pieces, which can be separately removed. Many 
species seem to be able to force off the lid of their pupa- 
rium, by merely pushing against it with their heads: 
but the common flesh-fly and many other Muscide, which 
are perhaps too feeble to effect this, or whose puparia 
are stronger than ordinary, are furnished with a very re- 
markable apparatus for this express and apparently sole 
purpose. ‘They are gifted with the power of introducing 
air under the middle part of the head, to which the an- 
tenne are fixed, and of inflating that part into a sort of 
membranous vesicle as big as the head itself; by the action 
of which against the end of the pupa-case, the lid is soon 
forced off. So powerful is this singular lever, that it is 
even sufficient to rupture the fibrous galls in which the 
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