This spider carries within its diminutive abdomen a secret which will
possibly serve to vex subtle intellects for a long time to come; for it
is hard to believe that merely by mechanical force, even aided by
currents of air, a creature half as big as a barley grain can
instantaneously snoot out filaments twenty or thirty inches long, and by
means of which it floats itself in the air.
Naturalists are now giving a great deal of attention to the migrations
of birds in different parts of the world: might not insect and spider
migrations be included with advantage to science in their observations?
The common notion is that the gossamer makes use of its unique method of
locomotion, only to shift its quarters, impelled by want of food or
unfavourable conditions--perhaps only by a roving disposition. I believe
that besides these incessant flittings about from place to place
throughout the summer the gossamer-spiders have great periodical
migrations which are, as a rule, in-visible, since a single floating web
cannot be remarked, and each individual rises and floats away by itself
from its own locality when influenced by the instinct. When great
numbers of spiders rise up simultaneously over a large area, then,
sometimes, the movement forces itself on our attention; for at such
times the whole sky may be filled with visible masses of floating web.
All the great movements of gossamers I have observed have occurred in
the autumn, or, at any rate, several weeks after the summer solstice;
and, like the migrations of birds at the same season of the year, have
been in a northerly direction.
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