SPINNING HABITS.
That which, more than any thing else, distinguishes spiders from other
animals is the habit of spinning webs. Some of the mites spin irregular
threads on plants, or cocoons for their eggs; and many insects spin
cocoons in which to pass through the change from larva to adult. In the
spiders the spinning-organs are much more complicated, and used for a
greater variety of purposes,—for making egg-cocoons, silk linings to
their nests, and nets for catching insects. The spider’s thread differs
from that of insects, in being made up of a great number of finer
threads laid together while soft enough to unite into one.
SPINNERETS.
[Illustration: Fig. 16.]
The external spinning-organs are little two-jointed tubes on the ends
of the spinnerets, Fig. 1, L. Fig. 16 is the spinnerets of the same
spider, still more enlarged to show the arrangement of the tubes. There
is a large number of little tubes on each spinneret, and in certain
places a few larger ones. Fig. 17 is a single tube, showing the ducta
which leads the viscid liquid to form the thread from a gland in the
spider’s abdomen. Each tube is the outlet of a separate gland. Fig. 18,
_a_, shows four small tubes from a spinneret of _Epeira_, each with a
small gland attached; and Fig. 18, _b_, a large tube, with one of the
large glands which extends forward the whole length of the abdomen,
Fig. 5, _u_.
[Illustration: Fig. 17.]
[Illustration: Fig. 18.]
The shape of the spinnerets, and size and arrangement of the tubes,
vary in different species. Fig. 19 is a spinneret of _Prosthesima_,
where there are a few large tubes in place of many small ones. In
_Agalena_ the two hinder spinnerets are long, and have spinning-tubes
along the under side of the last joint, Fig. 20.
When the spider begins a thread, it presses the spinnerets against
some object, and forces out enough of the secretion from each tube to
adhere to it. Then it moves the spinnerets away; and the viscid liquid
is drawn out, and hardens at once into threads,—one from each tube.
If the spinnerets are kept apart, a band of threads is formed; but,
if they are closed together, the fine threads unite into one or more
larger ones. If a spider is allowed to attach its thread to glass, the
end can be seen spread out over a surface as large as the ends of the
spinnerets, covered with very fine threads pointing toward the middle,
where they unite, Fig. 21.
[Illustration: Fig. 19.]
[Illustration: Fig. 20.]
The spinning is commonly helped by the hinder feet, which guide the
thread, and keep it clear of surrounding objects, and even pull it from
the spinnerets. This is well seen when an insect has been caught in a
web, and the spider is trying to tie it up with threads. She goes as
near as she safely can, and draws out a band of fine threads, which she
reaches out toward the insect with one of her hind-feet; so that it may
strike the threads as it kicks, and become entangled with them. As soon
as the insect is tied tightly enough to be handled, the spider holds
and turns it over and over with her third pair of feet, while, with the
fourth pair, she draws out, hand over hand, the band of fine threads
which adhere to the insect as it turns, and soon cover it entirely.
[Illustration: Fig. 21.]
It is a common habit with spiders to draw out a thread behind as they
walk along; and in this way they make the great quantities of threads
that sometimes cover a field of grass, or the side of a house. We often
see the points of all the pickets of a fence connected by threads spun
in this way by spiders running down one picket, and up the next, for no
apparent purpose.
Spiders often descend by letting out the thread to which they hang; and
are able to control their speed, and to stop the flow of thread, at
will. They sometimes hang down by a thread, and allow themselves to be
swung by the wind to a considerable distance, letting out the thread
when they feel they are going in the right direction.
Spiders in confinement begin at once to spin, and never seem
comfortable till they can go all over their box without stepping off
their web. The running spiders, that make no other webs, when about to
lay their eggs, find or dig out holes in sheltered places, and line
them with silk. Species that live under stones or on plants all line
their customary hiding-places with web, to which they hold when at
rest. Several of the large running spiders dig holes in sand, and line
them with web, so that the sand cannot fall in; and build around the
mouth a ring of sticks and straws held together by threads.
TRAP-DOOR NESTS.
The building of tubular nests is carried to the greatest perfection by
certain genera of the _Mygalidæ_. (See page 13.)
_Atypus_, the most northern genus of this family, makes a strong silken
tube, part of which forms the lining of a hole in the ground, and part
lies above the surface, among stones and plants, Fig. 22, A. The mouth
of the tube is almost always closed, at least when the spider is full
grown.
Another genus, which lives in warm countries, makes tubes lined with
silk, and closed at the top by a trap-door. A common species, _Cteniza
Californica_, lives in the southern part of California, and is often
brought east by travellers. It digs its hole in a fine soil, that
becomes, when dry, nearly as hard as a brick; but the spider probably
works when the ground is wet. The holes are sometimes nearly an inch
in diameter, and vary in depth from two or three inches to a foot.
The mouth is a little enlarged, and closed by a thick cover that fits
tightly into it, like a cork into a bottle. The cover is made of dirt
fastened together with threads, and is lined, like the tube, with silk,
and fastened by a thick hinge of silk at one side, Fig. 22, B. When the
cover is closed, it looks exactly like the ground around it. The spider
holds on the inside of the door with the mandibles and the two front
pairs of feet; while the third and fourth pairs of legs are pressed out
against the walls of the tube, and hold the spider down so firmly, that
it is impossible to raise the cover without tearing it.
Among the trap-door spiders of Southern Europe, about which Mr. J. T.
Moggridge has written a very interesting book, are species which make
different kinds of nests. The cover, instead of being thick, and wedged
into the top of the tube like a stopper, is thin, and rests on the top
of the hole, Fig. 22, C, and is covered with leaves, moss, or whatever
happens to be lying about; so that it is not easily seen. Two or three
inches down the tube is another door, Fig. 22, E, hanging to one side
of the tube when not in use; but, when one tries to dig the spider out
from above, she pushes up the lower door, so that it looks as if it
were the bottom of an empty tube.
Another species digs a branch obliquely upward from the middle of the
tube, closed at the junction by a hanging-door, which, when pushed
upward, can also be used to close the main tube, Fig. 22, F. What
use the spider makes of such a complicated nest, nobody knows from
observation; but Mr. Moggridge supposes that when an enemy, a parasitic
fly, for instance, comes into the mouth of the tube, the spider stops
up the passage by pressing up against the lower door; but, if this is
not enough, it dodges into the branch, draws the door to behind it, and
leaves the intruder to amuse himself in the empty tube. The branch is
sometimes carried up to the surface, where it is closed only by a few
threads; so that, in case of siege, the spider could escape, and leave
the whole nest to the enemy.
[Illustration: Fig. 22.
Trap-door nests: A, nest of Atypus; B, nest with thick door;
C, nest with thin door; D, branched nest; E, nest with two doors;
F, branched nest with two doors; G, nest with two branches.]
In these nests the spiders live most of the time, coming out at night,
and some species in the daytime, to catch insects, which they carry
into the tube, and eat. The eggs are laid in the tube; and the young
are hatched, and live there till able to go alone, when they go out,
and dig little holes of their own. As the spider gets larger, the hole
is made wider, and the cover enlarged by adding a layer of earth and
silk; so that an old cover is made up of a number of layers, one over
the other, over the original little cover.
Moggridge once took a _Cteniza Californica_ out of her nest, and put
her on a pot of earth, and the next morning had the good luck to see
her at work digging. She loosened the earth with her mandibles, and
took it in little lumps with the mandibles and maxillæ, and carried it
away piece by piece. It took her an hour to dig a hollow as large as
half a walnut. He saw the making of the door twice by other species.
Once he dug a hole for a spider in some earth, and the next day found
her in it, and the top covered by a little web, on which were scattered
bits of earth and leaves, which had evidently been put there by the
spider. The second night, enough dirt and silk were added to make the
door of the usual thickness; but the spider never finished it so that
it would open properly on its hinge. Another time Moggridge saw at the
mouth of a very small hole a spider at work making a door. She spun
a few threads across the hole, then gathered up with her front-legs
and palpi an armful of dirt, and laid it on top of them. She then got
under the pile, into the tube; but the motions of the dirt showed that
she was still at work on it, and next morning the under side had been
thickly covered with web, and the whole separated from the mouth of
the tube, except at one side, where the usual hinge was left. The new
door was at first soft, but in two or three days hardened, and appeared
exactly like an old door.
These spiders are accustomed to put on the door moss like that which
grows around it, and so conceal the door from sight; but when Mr.
Moggridge took away the moss, and dug up the ground around a hole, and
then destroyed the cover, the spider made a new one, and brought moss
from a distance to put on it, thereby making it the most conspicuous
thing in the neighborhood.
Mr. S. S. Saunders tried to see trap-door spiders make their nests.
When the earth was dry, they would do nothing; but, after watering it,
they several times dug new holes, but always in the night.
The food of the European trap-door spiders consists largely of ants and
other wingless insects, and they have been known to eat earthworms and
caterpillars. Mr. Moggridge has often seen them, even in the daytime,
open their doors a little, and snatch at passing insects, sometimes
taking hold of one too large to draw into the tube. One time he and
some friends marked some holes, and went and watched them in the night.
The doors were slightly open, and some of the spiders’ legs thrust out
over the rim of the hole. He held a beetle near one of the spiders; and
she reached the front part of her body out of the tube, pushing the
door wide open, seized the beetle, and backed quickly into the tube
again, the door closing by its own weight. Shortly after, she opened it
again, and put the beetle out alive and unhurt, probably because it was
too hard to eat. He next drove a sow-bug near another hole; and the
spider came out and snatched it in the same way, and kept it. None of
the spiders came entirely out of their holes, and they were only a
little more active than in the daytime.
Erber, in the Island of Tinos, noticed a place where several trap-door
nests were near each other, and spent a moonlight night watching them.
Soon after nine o’clock some of the spiders came out, fastened back
their doors, and each spun a web, about six inches long and an inch
high, among the grass near her hole, and went back into the tube.
In course of time beetles were caught in the webs, and eaten by the
spiders, and the hard parts carried several feet from the nest. The
next morning the webs had been cleared away, and the doors of the tubes
closed, leaving no traces of the night’s work.
SILK TUBES AND NESTS.
Several species of _Theridion_ and _Epeira_ make tents near their
webs, under which they hang when at rest, and in which some species
make their cocoons, and lay their eggs. The tents are usually covered
outside with leaves drawn together, with sticks or bud-scales collected
near by, or with earth and stones brought up from the ground below.
Some spiders living on plants make flat tubes, in which they wait for
insects, and also hide while moulting, or laying eggs. Others make,
especially about the breeding-time, bags of silk on plants, or under
stones, in which the egg-cocoons are finally spun.
[Illustration: Fig. 23.]
_Dolomedes_ makes among grass and shrubs, in meadows, a great nest,
four or five inches in diameter, Fig. 23, in which is the egg-cocoon.
The young hatch and ramble about in this nest for some time. The spider
remains near, usually holding on under the nest.
THE WATER-SPIDER.
There is one spider that makes a bag of silk, something like those
just mentioned, on water-plants, and lives in it under water, as in a
diving-bell; the opening being below, so that the air cannot escape.
Mr. Bell, in “The Journal of the Linnæan Society,” vol. i., 1857,
describes the filling of these nests with air by the spider. After the
nest had been made as large as half an acorn, she went to the surface,
and returned, fourteen times successively, and each time brought down a
bubble of air, which she let escape into the nest. The bubble was held
by the spinnerets and two hind-feet, which were crossed over them; and
the method of catching it was the following: The spider climbed up on
threads or plants nearly to the surface, and put the end of the abdomen
out of water for an instant, and then jerked it under, at the same time
crossing the hind-legs quickly over it. She then walked down the plants
to her nest, opened her hind-feet, and let the bubble go.
The water-spiders run about on water-plants, and catch the insects
which live among them. They lay their eggs in the nest; and the young
come out, and spin little nests of their own, as soon as they are big
enough. Their hairs keep the skin from becoming wet as they go through
the water; and in the nest they are as dry as if it were under a stone,
or in a hole on land.
COBWEBS.
The simple nests and tubes that have been described are made by
spiders, most of which spin no other webs. The larger and better known
cobwebs for catching insects are made by comparatively few species. On
damp mornings in summer the grass-fields are seen to be half covered
with flat webs, from an inch or two to a foot in diameter, which are
considered by the weatherwise as signs of a fair day. These webs remain
on the grass all the time, but only become visible from a distance when
the dew settles on them. Fig. 24 is a diagram of one of these nests,
supposed, for convenience, to be spun between pegs instead of grass.
The flat part consists of strong threads from peg to peg, crossed by
finer ones, which the spider spins with the long hind-spinnerets, Fig.
20, swinging them from side to side, and laying down a band of threads
at each stroke. The web is so close and tight, that one can hear the
footsteps of the spider as she runs about on it. At one side of the web
is a tube leading down among the grass-stems. At the top the spider
usually stands, just out of sight, and waits for something to light on
the web, when she runs out, and snatches it, and carries it into the
tube to eat. If any thing too large walks through the web, she turns
around, and retreats out of the lower end of the tube, and can seldom
be found afterward. In favorable places these webs remain through the
whole season, and are enlarged, as the spider grows, by additions on
the outer edges, and are supported by threads running up into the
neighboring plants. Similar webs are made by several house-spiders, and
are enlarged, if let alone, till they are a foot or two feet wide, and
remain till they collect dirt enough to tear them down by its weight.
[Illustration: Fig. 24.]
Nearly all spiders that make cobwebs live under them, back downward;
and many are so formed, that they can hardly walk right side up. The
spiders of the genus _Linyphia_ make a flat or curved sheet of web,
supported by threads above and below; the spider standing, usually,
underneath in some corner, out of sight. _Linyphia Marmorata_ makes a
dome-shaped web, Fig. 25, supported by threads that extend up into the
bushes two or three feet. The spider stands under the middle of the
dome, where it draws in a small circle of web with its feet. The upper
threads of the web interfere with the wings of small insects flying
between them, and they fall down to the dome below, where they are
seized, and pulled through the nearest hole. _Linyphia communis_ makes
a double web, Fig. 26. The spider stands under the upper sheet, which
curves a little downward. What the use of the lower web is, is not
easily seen. Either of these spiders, when frightened, leaps out of the
web to the ground; but _Linyphia communis_ must go to the edge before
she can clear herself, and so is easily caught in her own web.
[Illustration: Fig. 25.]
[Illustration: Fig. 26.]
A little spider, _Argyrodes_, belonging to the same family, lives among
the upper threads of webs of this kind, without being troubled by the
owner. It resembles in size and color the scales of pine-buds that
often fall in the web, and may easily be mistaken for them. It probably
spins a few threads of its own among the borrowed ones, and does, at
times, make a separate web of its own.
The webs of _Theridion_ usually have at some part a tent, or at least
a thicker portion, under which the spider stands; and from this run
irregularly simple threads, crossing each other in all directions, and
held in place by threads above and below. Such irregular webs are made
often in houses by _Theridion vulgare_, Hentz, in corners of rooms,
under furniture, and in cellar-stairways. The same spider spins
occasionally out of doors on fences, but never on plants. When it
has caught an insect, and tied it up, it hoists it up into the web,
sometimes a considerable distance.
They do this by fastening to it threads from above, which, as they dry,
contract, and pull it up a little. They keep on bringing down more and
more threads, until the insect is at last hoisted to the top of the
web, where they can suck it without exposing themselves.
_Pholcus_, the long-legged cellar-spider, makes an irregular web of
this kind, and has a curious habit when alarmed. It hangs down by its
long legs, Fig. 27, and swings its body around in a circle, so fast
that it can hardly be seen. Fig. 27, _a_, represents the spider as seen
from below; and the dotted circle shows the path in which it revolves.
ROUND WEBS.
These well-known cobwebs are made by the family _Epeiridæ_, Figs. 1, 4;
and the process of making them by the common spider, from which these
figures are drawn, can be easily observed in any garden. They generally
choose for their web a window-frame or fence, or some such open wooden
structure, where there is a hole or crack in which they can hide in the
daytime.
[Illustration: Fig. 27.]
[Illustration: Fig. 28.]
The spider begins by spinning a line across where the web is to be, and
attaches another to it near the middle. She carries the last line along,
holding it off with one of the hind-feet, and makes it fast an inch
or two from one end of the first; then she goes back to the centre,
attaches another line, which she carries off in another direction,
and fastens; and so on, until all the rays of the web, Fig. 28, are
finished. She stops occasionally at the centre, turns around, and
pulls at the threads one after another, and spins here and there short
cross-lines to hold them more firmly. She seems, by thus feeling the
rays, to decide where to put in the next one, and does it always in
such a way as to keep tight what has been done before. When the rays
are finished to her satisfaction, the spider begins at the centre to
spin a spiral line across them, Fig. 28, _a_, _a_, _a_; the turns of
the spiral being as far apart as the spider can conveniently reach. She
climbs across from one ray to the next, holding her thread carefully
off with one of the hind-feet, till she gets to the right point, and
then turns up her abdomen, and touches the ray with her spinnerets,
thus fastening the cross-thread to it. The figure shows her in this
position. When this spiral has been carried to the outside of the web,
the spider begins there another and closer one, Fig. 28, of thread of
a different kind. While the first thread was smooth, the latter is
covered with a sticky liquid, which soon collects on it in drops, and
makes it adhere to any thing that touches it. After going round a few
times, this spiral crosses the one that was spun first, or would, if
the spider allowed it to; but, as she comes to the old spiral, she
bites it away, leaving only little rags, Fig. 22, _b_, attached to
the rays, which may be seen in the finished web. By beginning thus at
the outside, the spider is able to cover the whole web with adhesive
threads, and, without stepping on it, take her usual place in the
centre. She usually is careful enough to spin beforehand a thread from
the centre to her nest, and sometimes stays there, with one foot on the
thread, so as to feel if any thing is caught in the web. When she feels
a shake, she runs down to the centre, feels the rays to see where the
insect is, and runs out, and seizes it, or ties it up as described on
page 43. We have described the web as consisting of one regular spiral;
but this is seldom the case. It is usually wider on one side than the
other, or below than above, as in Fig. 28, where outside the spirals
are several loops going partly round the web. The web of Zilla consists
entirely of such loops going three-quarters round the web, and
returning, leaving a segment without any cross-threads, in which is
the line from the centre to the spider’s nest, Fig. 29. The spider is
shown carrying a fly to its nest attached to the spinnerets; and, if
this is its usual habit, the web with an open segment is certainly more
convenient than a complete one.
[Illustration: Fig. 29.]
The web of _Nephila plumipes_, described by Wilder, consists also of
loops running round about quarter of a circle, Fig. 30; and in this
web the smooth cross-lines which are first spun are not removed, but
remain after it is finished. Fig. 31 shows part of one side of a web;
the arrows marking the smooth thread, and the direction in which it was
spun.
[Illustration: Fig. 30.]
_Argiope_, the large black and yellow autumn spiders, cross the middle
of the web with a zig-zag band of white silk, which, as the web is
obliquely hung, partly conceals the spider under it. These spiders also
spin each side of the web, and two or three inches from it, a screen of
irregular threads of unknown use.
[Illustration: Fig. 31.]
The round-web spiders are said to repair their webs by tearing out a
dirty, tangled piece, and putting a new one in its place. Wilder says
that _Nephila plumipes_ tears off and replaces half the web at one
time. _Epeira vulgaris_ often takes away an old web, and puts a new one
in the same place, tearing down the old in pieces, and putting in the
rays of the new as it goes along. The spider walks on the nearest sound
thread, and gathers in with her front-feet as much old web as she can
tear off, and rolls it up with her palpi and mandibles into a ball,
and, when it is tight enough not to stick to the web, drops it. As she
walks along, gathering up the old web in front, she at the same time
spins a new thread behind, and, when she gets to a suitable place,
makes it fast as one of the rays of the new web. The common story has
it, that the spider eats the old web. She certainly gathers it up in
her mouth, and sometimes throws it away at once, but at other times
sits and chews it a long time, with apparent pleasure.
Most of the _Epeiridæ_ are brightly colored, and make no attempt at
concealment when in the web. Others have odd shapes and colors, and
hang in the web in such positions that they look like any thing but
animals. Some species draw up their legs against their triangular
abdomens, and look like bits of bark fallen into the web. Others are
long and slender, and when at rest, either in the web or out, lay their
legs close together before and behind their bodies, so as to look like
straws. Others have oddly shaped abdomens, as Fig. 32, under which the
rest of the body is partly concealed.
[Illustration: Fig. 32.]
_Epeira caudata_, a common gray spider, living in the wood, collects
pieces of insects and other rubbish, and arranges it in a line up and
down, across the centre of the web. The spider stands in the centre,
and from a short distance can hardly be distinguished from the rubbish.
She also hides her cocoons in the web, in the same line of dirt.
The size of the web is usually proportioned to that of the spider; but
_Epeira displicata_, which is quarter of an inch long, makes a web only
two or three inches in diameter, on the ends of branches of bushes,
where it is shaken about, and sometimes blown to pieces, by the wind.
As the spider stands in her web, and feels a slight shake, such as
would be caused by a sudden wind, she draws her legs together, pulling
the rays tighter, and so making the whole web steady. If, however, the
spider is frightened, and has no time to escape, she throws her body
back and forth as a man does in a swing, and thus shakes the web so
rapidly, that the spider can hardly be seen. The most usual habit, when
alarmed, is to drop to the ground, and lie there as if dead.
USE OF SPIDER’S SILK.
Various attempts have been made to use the silk of spiders, and chiefly
that of the large round-web spiders, for practical purposes, either by
carding the cocoons, or by drawing the thread directly from the spider.
The latest experiments and plans for this purpose are those of
Professor Wilder in “The Galaxy,” vol. viii. He shows how _Nephila
plumipes_ might be raised in large numbers, each spider kept by herself
in a wire ring surrounded by water, fed with flies bred for the purpose
from old meat, and milked every day of their thread. Each cocoon of
this spider contains from five hundred to a thousand eggs. The young
live together for two or three weeks, spin a web in common, and eat
one another, or any small insects that come in their way. Then they
begin to scatter, and each builds her own web; so that from this time
they must be kept separate, or they would eat one another. Every day or
two, each spider should be taken down, put into a pair of stocks, and
the thread pulled out till it stops coming. In this way Wilder thinks
an ounce of thread could be got from each spider during the summer.
The thread is from a seven-thousandth to a four-thousandth of an inch
thick, and much smoother and more brightly colored, as well as finer,
than that of the silk-worm. Several threads would have to be twisted
together to get one of manageable size. The principal difficulties are
the space needed for keeping each spider by herself, and the amount of
labor needed to provide them with living insects for food, and to draw
out the silk, which would make it too expensive to use.
CURLED WEBS.
There is a family of spiders called by Blackwall _Ciniflonidæ_, see
p. 17, which, besides the usual plain thread, make a peculiar kind of
their own. They have in front of the spinnerets, Fig. 33, an additional
spinning-organ called the cribellum, _a_, _a_. It is covered with fine
tubes, much finer than those of the spinnerets, set close together.
[Illustration: Fig. 33.]
They also have on the last joint but one of the hind-legs a comb of
stiff hairs, called the calamistrum, Fig. 34, on the upper side.
[Illustration: Fig. 34.]
[Illustration: Fig. 35.]
When they spin their peculiar web, they turn one of the hind-legs
across under the spinnerets, so that the calamistrum is just under
the cribellum, and the foot rests on the opposite leg, Fig. 35.
The hind-legs are then moved rapidly back and forth; so that the
calamistrum combs out from the spinning-tubes, and at the same time
tangles a band of fine threads, C. This band is laid along, and
attached here and there to a plain thread, A, B, so as to make it
adhere more readily to an insect that happens to touch it. As one leg
gets tired, they change, and work with the other. In the webs of these
spiders this adhesive band can be seen with the naked eye, running
about, as in Fig. 36. The webs are usually irregular, and shaped to
fit the place where they are built, but have, in some part, a tube
somewhat like that of the grass spider, Fig. 24, where the owner hides.
Sometimes they are more or less regular in structure, some of the
threads being parallel, and crossed by shorter ones at regular
intervals, Fig. 37. Others are circular, with a tube in the centre
which runs into a crack, and from which radiate irregularly the
principal threads of the web. Such webs are sometimes very numerous
on stone buildings, and, as they collect large quantities of dust,
seriously disfigure them. The webs alone, when clean, would not be
noticed.
[Illustration: Fig. 36.]
[Illustration: Fig. 37.]
THE TRIANGLE SPIDER.
Among those spiders that use the calamistrum is one which makes a
web unlike any other. It has been described by Professor Wilder, in
the “Popular Science Monthly” for April, 1875, under the name of the
“triangle spider.” It lives usually among the dead branches around the
lower part of pine and spruce trees, and is colored so like the bark,
that when it stands, as it usually does, on the end of a branch, it
is easily mistaken for a part of it. The web seems to be made in the
night. Wilder saw them early in the morning; and I, in the evening,
between sunset and dark. A single thread five or six inches long runs
from the spider’s roost; and from its extremity radiate four branches,
attached to various twigs in the neighborhood, Fig. 38, AE, AF, AG, AH.
[Illustration: Fig. 38.]
The spider begins to cross them with adhesive threads near the end
of the upper ray at S′. After fastening the end of the thread, she
walks along toward the centre, scratching away all the time with her
calamistrum, till she comes to a place, 5, where she can cross to the
next ray. She crosses over, and goes outward toward S″, the thread
shrinking as she goes, until, when she arrives at S″, it is just long
enough to reach across to S′. She fastens it by laying it along the ray
for a short distance, and goes inward again till she reaches 7, where
she crosses to the next ray; and so on till the thread is finished to
S‴′. Here she stops spinning, and goes up the lower ray to A, and along
the upper one to 4, where she starts another cross-thread. This goes on
till the whole web is filled, as in Fig. 39, nearly to the centre.
When the web is finished, the spider goes up the thread A _o_, to
within an inch or so of the twig to which it is fastened; turns round,
and takes hold of the thread with her front-feet; then pulls herself
backward with her hind-feet up to the twig. She thus tightens the web,
and draws up a loop of thread between her front and hind feet, Fig. 39,
lower figure.
[Illustration: Fig. 39.]
The net is now set for use, and she stands holding it till something
touches it; then she lets go with her hind-legs, and the net springs
forward, bringing more threads into contact with the insect, and
sliding the spider along the line toward A. If she thinks it worth
while, she draws up another loop, and snaps the web again. When she is
satisfied that the insect is caught, she gathers up part of the web
till she comes to him, covers him with silk, and carries him up to her
roost.
There are other spiders of this group that make round webs, just like
those of the _Epeiridæ_, Fig. 28, except in the adhesive threads being
spun with the calamistrum.
FLYING SPIDERS.
Often, in summer, the bushes are covered with threads, attached by one
end, blowing out in the wind; and bits of cobweb are blowing about,
with occasionally a spider attached. To account for such threads,
curious theories have been thought of; among others, that spiders are
able to force the thread from their spinnerets, like water from a
syringe, in any direction they choose.
If a spider be put on a stick surrounded by water, she manages, in
course of time, to get a thread to some object beyond, and to escape by
it. To find out how this is done, Mr. Blackwall tried some experiments.
He put spiders on sticks in vessels of water, and they ran up and down,
unable to escape as long as the air in the room was still. But, if
a draught of air passed the spider, she turned her head toward it,
and opened her spinnerets in the opposite direction. If the draught
continued, a thread was drawn out by it, which at length caught upon
something, when the spider drew it tight, and escaped on it. If the air
was kept still, or the spider covered with a glass, she remained on the
stick till taken off.
These experiments have been repeated, and show that the spider does not
shoot or throw the web in any way, but takes advantage of currents of
air, and allows threads to be blown out to a considerable distance.
There is a still more curious use of this method of spinning threads;
that is, in flying. Small spiders, especially on fine days in the
autumn, get up on the tops of bushes and fences, each apparently
anxious to get as high as possible, and there raise themselves up on
tiptoe, and turn their bodies up, as in Fig. 40, with their heads
toward the wind, and spinnerets open. A thread soon blows out from the
spinnerets, and, if the current of air continues, spins out to a length
of two or three yards, and then offers enough resistance to the wind
to carry the spider away with it up into the air. As soon as she is
clear, the spider turns around, and grasps the thread with her feet,
and seems to be very comfortable and contented till she strikes against
something. Sometimes they rise rapidly, and are soon out of sight; at
other times blow along just above the ground.
[Illustration: Fig. 40.]
This habit is not confined to any particular kinds of spiders, but is
practised by many small species of _Erigone_, and by the young of many
spiders of all families, that, when adult, would be too large for it.
The majority of the spiders flying in autumn are the young of several
species of _Lycosa_, that seem to spend the greater part of October and
November trying to get as far above ground as possible. The best places
to watch them are garden-fences in cities, where they often swarm, and
can be more distinctly seen than on bushes. Large numbers can always
be seen, for example, on the fences around the Common in Boston, every
fine day in autumn, until there has been a long period of cold weather.
Other species fly in the early part of summer.
Mr. Blackwall observed in Manchester, Eng., Oct. 1, 1826, a calm sunny
day, that, just before noon, the fields and hedges were covered over
with cobwebs. So thick were they, that, in crossing a small pasture,
his feet were covered with them. They had evidently been made in a very
short time, as early in the morning they were not conspicuous enough
to attract his attention, and the day before could not have existed at
all, as a high wind blew all day. At the same time large rags of web
were floating about in the air, one measuring five feet long, and
several inches wide. These appeared to be not formed in the air, but
torn from grass and bushes, where they were produced by the tangling of
many threads which had been spun separately. They kept rising all the
forenoon, and in the afternoon came down again. Not one in twenty had
a spider on it. Similar large webs were observed by Lincecum in Texas,
and supposed by him to be balloons spun purposely by the spiders.
Mr. Darwin, in the journal of the voyage of “The Beagle,” says, that
when anchored in the River Plata, sixty miles from shore, he has seen
the rigging covered with cobwebs, and the air full of pieces of web
floating about. The spiders, however, when they struck the ship, were
always hanging from single threads, and never to the floating webs.
A recent account of the signs of weather-changes near the southern
coast of the United States mentions as one of them cobwebs in the
rigging.
It is still unexplained how the thread starts from the spinnerets. It
has been often asserted that the spider fastens the thread by the end,
and allows a loop to blow out in the wind; but, in most cases, this is
certainly not done, only one thread being visible. Sometimes, while
a thread is blown from the hinder spinnerets, another from the front
spinnerets is kept fast to the ground, Fig. 41; so that, when the
spider blows away, it draws out a thread behind it entirely independent
of the one from which it hangs.
[Illustration: Fig. 41.]
Sometimes, instead of a single thread, several are blown out at once,
like a long brush, as in Fig. 42, which represents, four times
enlarged, an unusually large spider just before blowing off a fence.
[Illustration: Fig. 42.]