1878. ] Extrication of Silkworm Moths. 379 
THE MODE OF EXTRICATION OF SILKWORM MOTHS 
FROM THEIR COCOONS. 
BY A. S. PACKARD, JR. 
ITHOUT" having made extended research in the literature 
of entomology, the only account which we have been able 
to find of the mode of extrication of the silkworm moths from 
their cocoons is that given by Kirby and Spence in their chapter 
on the pupa state of insects, vol. iii, pp. 280-283, which is quoted 
below, as it gives a summary of what was known up to the year 1828, 
while so far as we are aware nothing has since then been recorded 
on this interesting subject, except the observations of Mr. L. Trou- 
velot (AMERICAN Natura ist, vol. i, pp. 33, 34); the brief state- 
ment in Lacordaire’s Introduction a l’Entomology (1834, p. 201) 
being evidently based on Réaumur’s observations. 
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 par- 
ticularly careful to guard against, by exposing the cocoon to heat 
sufficient to destroy the included pupa. The question is, what 
instruments does the moth employ to effect this? And this we 
are not able to answer satisfactorily. 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 Réaumur 
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 actually cut asunder. He therefore 
infers that the eyes, which are the only hard organs of the head, 
are the instruments by which the threads are divided—their 
numerous minute facets serving the purpose of a fine file It 
should be observed, however, that Mr. Swayne confirms Mal- 
pighi’s assertion that the silk worm does not cut but merely pushes 
aside the threads of its cocoon, and he informs us that he has 
proved the fact by unwinding a pierced cocoon, the thread of 
which was entire. Yet Réaumur’s correctness cannot be sus- 
pected, and he affirms that from observation there can scarcely 
be a doubt that most of the threads are broken; which is further 
confirmed in an account of the breeding of silkworms published 
in the American Philosophical Transactions, in which it is ex- — 
pressly stated that cocoons out of which the fly has escaped , 
cannot be wound, Analogy, it must be confessed, is against 
Réaumur’s opinion, since other kinds of silkworms make their  — 
