280 STATES OF INSECTS. (Pupa.) 
I am next to give you some account of the second 
mode in which the release of the perfect insect from 
its cocoon is effected—that, namely, wherein its own 
exertions chiefly accomplish the work. I shall from a 
large number select only a few instances. The texture 
of the cocoon of the silkworm-moth is uniform in every 
part, and the layers of silk are equally thick at both 
ends. The moth makes its way out by cutting or 
breaking these threads at the end ‘opposite to its head: 
an operation which, as it destroys the continuity of 
the silk, those who breed these insects are particularly 
careful to guard against, by exposing the cocoon to 
heat sufficient to destroy the included pupa. The ques- 
tion is—What instruments does the moth employ to 
effect this? And this we are not able to answer satis- 
factorily. Malpighi asserts that the animal first wets the 
silk with a liquid calculated to dissolve the gum that 
connects the threads, and then employs its lengthened 
head to push them aside and make an opening?. But, as 
Reaumur has observed, besides that so obtuse a part as 
the head of a moth is but ill fitted to act as a wedge, we 
find the threads not merely pushed to each side, but ac- 
tually cut asunder. He therefore infers that the eyes, 
which are the only hard organs of the head, are the in- 
struments by which the threads are divided—their nu- 
merous minute facets serving the purpose of a fine file?. 
It should be observed, however, that Mr. Swayne con- 
firms Malpighi’s assertion, that the silkworm does not 
cut, but merely pushes aside, the threads of its cocoon, 
and he informs us that he has proved the fact, by un- 
winding a pierced cocoon, the thread of which was en- 
* De Bombyc. 29. > Reaum. i. 624. 
