AGELENA
Before going farther afield, let us investigate one of the spinners
of the sheet-webs that are so unpleasantly familiar in the house. We
object to them on very obvious grounds, first as evidence of neglect
and bad housewifery, and secondly as repulsive objects when covered by
accumulations of dust which their firm texture and their durability
make inevitable.
The common house-spiders belong to the family Agelenidae. It is quite
likely that their original home was in a warmer climate where they
lived out of doors, but that was long ago, and now they uniformly
select buildings of some sort for their operations. They have, however,
even in this country, several open-air cousins, and most people know
the great sheet-web spider of the hedge-rows, though its name—_Agelena
labyrinthica_—may be new to them. Its web consists of a closely woven
wide-spreading sheet connected with a tube of even denser material, in
the mouth of which the spider may generally be seen lurking, a rather
sinister object. If a better view of the animal is desired it is only
necessary to agitate the web slightly and the spider runs forward to
investigate. It is a large species as British spiders go—about three
quarters of an inch in length—with the abdomen rather prettily marked
with oblique white streaks.
It is very unlike our garden spider in certain points of structure;
its body is more elongate and rather rigid, with little play of action
between the cephalothorax and the abdomen; its legs are notably long,
and so are two of its spinnerets, which can be seen protruding beyond
the abdomen as we look down upon it.
But we shall gain little information by looking at the completed
web, and our best plan is to take the animal home and observe it
in captivity. We have prepared for its reception a box about a foot
square, with a gauze top and a movable glass front.
It is not such an easy matter to secure the spider, which can run like
a lamp-lighter, and which has a way of escape at the lower end of its
tube. The safest way is suddenly to shut off this means of retreat with
the finger and thumb of the left hand and simultaneously to present a
glass phial at the mouth of the tube; the spider runs up into it and
is taken without the risk of injury. It is never advisable to handle
spiders, not because any British species is formidable, but because
they so readily part with their limbs in order to escape, and the
chances are that only a mutilated specimen will be obtained.
Now _Agelena_ does not seem to be a particularly engaging pet, but
it has its points. In the first place, it very quickly makes itself
at home; a short time is spent in exploring its new quarters, but it
adapts itself almost at once to its changed situation. Moreover it
is of a peaceable and domestic disposition and the male and female
live amicably together, which is far from being the case among
the Epeiridae, whose peculiar marital relations are often—quite
wrongly—attributed to the whole tribe of spiders. A male garden-spider
courts the female at the risk of his life, and it is not surprising
that he should evince great hesitation and caution in his advances. If
his attentions are unwelcome, or even if they have been accepted, he
will be promptly trussed up and eaten unless he beats a hasty retreat.
But with _Agelena_ the conjugal relations are exemplary, and harmony
reigns in the home. The question of food is certainly a difficulty,
but if insects are let loose in the cage the spider will attend to the
catching of them. In some cases raw meat has been found a satisfactory
substitute.
After a brief exploration of the box the captive soon becomes busy,
going to and fro across its cage and attaching lines to the sides at
some height up from the floor. So fine is the work that for a long
time hardly anything is visible, and the movements of the animal are
the only clue to what is taking place. By and by it becomes evident
that a sort of skeleton platform has been spun across the box, upon
which the spider is able to walk. It is continually strengthened by
new threads, and braced by stay-lines above and below. It has been
hardly possible to follow the operations by which this has come about,
and even now we are chiefly aware of the existence of the platform
because we see the spider walking upon it; its movements seemed very
scrambling and unmethodical, but they have resulted in the foundation
of the sheet-web and its terminal tube. But now it begins to behave
quite differently, and another phase of the work has clearly begun;
it crawls about over the almost invisible foundation lines with a most
curious gait, using its long legs to sway its body from side to side,
raising and depressing its abdomen at intervals, and as this motion
continues a beautiful gauzy sheet of incredibly fine texture gradually
grows into view. What is happening is that the spider is strewing over
the foundation lines multitudinous threads from its long posterior
spinnerets, which are beset on their under surface with numbers of
hair-like spinning tubes from each of which the silk is issuing. All
day long the process goes on, and by slow degrees the web increases in
density. Indeed for days after the structure is complete the spider
spends odd moments in going over the ground again till the sheet, and
especially the tube proceeding from it to a corner of the box, are so
closely woven as to have become almost opaque, and its occupant at
length appears to be satisfied with his handiwork, and retires into the
tube to wait patiently for casual visitors.
July is a good month in which to experiment with _Agelena_, for if the
captives include female specimens some further spinning operations of
a very complicated description may be observed. The time of egg-laying
is at hand and elaborate preparations have to be made, but if the
experimenter wishes to see the whole process he must be prepared
to sacrifice his night’s rest, for the most critical part of the
performance takes place in the small hours of the morning. We will
describe what occurred in the case of one _Agelena_.
The approaching oviposition was heralded several hours beforehand by
the animal commencing to weave a hammock-like compartment from the roof
of the box and above the sheet-web. This chamber was about four inches
long and was constructed precisely in the same manner as the sheet, to
which it was braced by lines from various points of its under surface.
Its construction occupied the whole day previous to the laying of the
eggs, and not until half an hour before midnight was it completed.
Within this compartment, close to the roof, the spider next wove a
small sheet one inch long, working diligently in an inverted position,
ventral surface upwards. After a quarter of an hour it rested for an
equal space, apparently exhausted by its prolonged efforts. An hour
and three quarters intermittent work served to complete the sheet,
the spider varying the monotony of its sinuous walk round this small
area by occasionally walking over it and strengthening the lines which
attached its angles to the roof.
[Illustration: Fig. 5. _Agelena_ weaving her egg-cocoon.]
A marked change now became observable in the manner of working. The
animal abandoned its incessant to and fro motion but began to jerk its
body up towards the sheet, throwing silk strongly against it. At the
same time the posterior spinnerets were actively rubbed together and
the long posterior spinnerets separated and brought together again
with a scissor-like action. The result of this performance was to
invest the under surface of the small sheet with a coating of flossy
silk quite unlike the ordinary web in texture, the purpose of which
soon became evident, for at about a quarter past two the spider began
to deposit its eggs _upwards_, against this loose-textured silk,
aiding the egg-mass to adhere by occasional upward jerks of the
body. This occupied between five and ten minutes, and as soon as it
was accomplished the under surface of the egg-mass was covered by a
layer of flossy silk similar to that against which it was laid, the
eggs being thus entirely enveloped in a coating of soft loose-textured
material. This was next covered in by a sheet of firm texture like that
of the original web.
It might be supposed that the work was at length finished and that
a well-earned rest might be enjoyed, but this was far from being
the case. The spider remained as active as ever though an hour or
two passed before the object of its industry was evident. All this
time it was incessantly climbing backwards and forwards between the
egg-sheet and the hammock and generally scrimmaging round in the most
unaccountable way, but it gradually became evident that the eggs were
being enclosed in a wonderful transparent box of filmy silk with the
egg-bearing sheet for its roof. By nine o’clock it was of moderate
strength and opacity, and the spider, having worked “the clock round,”
no longer laboured continuously. Days elapsed, however, before it was
entirely finished to the satisfaction of the spider, which remained all
the time in close proximity to the box and could with difficulty be
frightened away, but clung tenaciously to it when interfered with.
Now this remarkable performance, which any reader endowed with
sufficient patience may observe for himself, gives food for thought.
The spider has never seen a cocoon constructed and has no model to
work by, and yet it performs with absolute precision all the stages,
in their proper succession, of a work which involves quite a number of
different spinning operations, nor does the absence of light by which
to work trouble it in the slightest. It seems hard to believe that this
is not a sign of high intelligence and that the spider is probably
quite unconscious of the object for which it has laboured so long and
so aptly. But how otherwise explain this curious fact? If the eggs are
removed the moment they are laid the work is continued precisely as if
they were still there. The box is laboriously built round the place
where they ought to be, and the spider refuses to budge from the empty
casket, though there is no longer any treasure to guard.
Clearly as the egg-laying time approaches the spider feels an
irresistible blind impulse to perform in a definite order certain
complicated actions. It is like a machine actuated by an internal
spring, and in the spider’s case the internal spring is the inherited
nervous mechanism we call instinct, which urges it to actions which it
is not in the least necessary that it should understand.