STATES OF INSECTS. (Pupa.) 275 
of a silken ball, through which the finger could not be 
easily pushed? Or the puss-moth (Cerura Vinula) 
pierce the walls of its house of glue and wood, which 
scarcely yield to the knife? You will not doubt that 
these difficulties have been foreseen by Inrinite Wis- 
pom, and provided against by InrinrrE Power. ‘The 
egress of moths from their cocoons is secured in two 
ways ;—either by some peculiarity in the first construc- 
tion of the cocoon by the caterpillar, or by some process 
which the pupa or perfect insect is instructed to perform. 
As examples of each, several curious instances may be 
cited. 
The larva of the moth which about 1760 made such 
havoc in the province of Angoumois in France, becomes 
a pupa in the interior of the grain of wheat which it has 
excavated; but the opening by which it first entered is 
not bigger than a pin’s point, and is quite insufficient for 
the egress of the moth. How, then, is the latter to force 
its way through the tough skin which surrounds it? The 
larva, previously to assuming the pupa state, gnaws out 
a little circular piece at that end of the grain where the 
head of the future moth would lie, taking care not to 
detach it entirely. At this little door, which is sufficient 
to protect it from intruders, the moth has but to push, 
when it falls down, and leaves a free passage for its exit. 
A contrivance almost similar is adopted by a caterpillar 
which feeds in the interior of the heads of a species of 
teazel (Dipsacus), for a minute and interesting history 
of which we are indebted to Bonnet. This caterpillar 
previously to its metamorphosis actually cuts a cir- 
cular opening in the head, sufficiently large for the 
egress of the future moth; but to secure this sally-port 
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