When spring has sufficiently advanced for the leaves of the elm and
the hop to be fairly well developed, the mother butterflies lay their
eggs in a curious and characteristic fashion. Under a lens these eggs
look like tiny barrels with vertical ribs. They are deposited in
columns, the egg first extruded being attached to the leaf, generally
the under surface, and those which follow are placed one upon the
other sometimes to the number of six or eight, the group thus making a
miniature column. Now if the egg which was first laid should hatch
before the others, when the little caterpillar came out it would be
very likely to cause the others to fall off and when they hatched they
would find themselves in what would be to them an impenetrable forest
of weeds and grasses from which there would be small chance to escape
to reach the elm or hop leaves. To avoid this calamity we find an
interesting adaptation. The egg at the end of the column hatches
first, although it was necessarily the one laid last. The tiny
caterpillar eats its way out of the shell and crawls over the other
eggs to the leaf. Then the others hatch in succession.
The eggs thus deposited by the hibernating butterflies are likely to
be laid late in May or even early in June. They hatch into
caterpillars less than a week later and these caterpillars feed for
about a month, when they change to the characteristic chrysalids in
which they commonly remain for a week or ten days. They then emerge as
the summer brood of butterflies, most of them in New England appearing
during July. These remain upon the wing for several weeks, the females
laying their eggs upon the elm and hop leaves. These in turn soon
hatch into caterpillars that change to chrysalids in August and emerge
as butterflies late that month or during September. This autumn brood
of butterflies is quite abundant for a time but soon seeks the
seclusion of winter quarters to remain until the following April.
There are thus two distinct broods during the year in the Northern
states while as far south as West Virginia there are likely to be
three broods.
These caterpillars at first simply eat small holes in the green
substance of the leaf, but as they become larger each takes up its
abode on the under surface of a single leaf and makes a sheltered tent
in somewhat the same fashion that the Painted Lady does upon the
nettle leaf. The caterpillar eats out more or less of the base of the
blade on each side of the midrib, thus weakening the edges so that
they can be fastened in a tent-like manner by silken threads. This
serves as a resting place from which it sallies forth to feed,
commonly only toward the tip of the leaf. As a result it often eats
itself out of house and home and has to crawl to another leaf and
construct a new shelter.
Public-domain text, read in full here on John Shaqi.
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