In the case of the twins, the cocoon of the female was
the larger; but I have known male and female alike to emerge from
large or small. You are fairly sure of selecting a pair if you
depend upon weight. The females are heavier than the males, because
they emerge with quantities of eggs ready to deposit as soon as they
have mated. If any one wants to winter a pair of moths, they
are reasonably sure of doing so by selecting the heaviest
and lightest cocoons they can find.
In the selection of cocoons, hold them to the ear, and with a
quick motion reverse them end for end. If there is a dull, solid
thump, the moth is alive, and will emerge all right. If this thump
is lacking, and there is a rattle like a small seed shaking in a
dry pod, it means that the caterpillar has gone into the cocoon
with one of the tiny parasites that infest these worms, clinging
to it, and the pupa has been eaten by the parasite.
In fall and late summer are the best times to find cocoons, as
birds tear open many of them in winter; and when weatherbeaten
they fade, and do not show the exquisite shadings of silk of those
newly spun.
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