WOLF-SPIDERS
Of the groups of wandering spiders, which spin no snare but trust to
speed and agility for their food, the Lycosidae or wolf-spiders supply
the best subjects for study. To begin with, they are very numerous
at certain times of the year, some species absolutely swarming in
woods during May and June among the leaves which fell in the previous
autumn. During the summer months they are still in evidence, but
as winter approaches they rapidly disappear. The swift motion and
predaceous habits have earned them the name of wolf-spiders, but
though they sometimes occur in incredible numbers so that it seems
impossible to avoid treading upon them, they do not hunt in packs; each
one is entirely concerned with his own individual quarry. They are
moderate-sized or large spiders—commonly about half an inch long in
this country though there are exotic species which attain an inch and
a quarter—and in build they are very unlike the garden-spider, being
elongate, and with the abdomen nothing like so globular.
Their habits vary considerably. One genus, appropriately named
_Pirata_, is semi-aquatic, living at the margins of rivers and ponds,
and able to run on the surface of the water, but most of the Lycosidae
prefer dry land—the dryer the better. Heaths, sandhills, bare and
stony stretches of soil, even deserts, are fertile in examples of this
group. Most of the smaller species love the sunlight, and it is often
noticeable on a bright day, when the ground seems to be alive with
wolf-spiders, that a chance cloud obscuring the sun will cause them to
disappear as if by magic.
Some of the small Lycosids seem to be absolute wanderers, having
no home at all, but spending the night under a stone or any casual
shelter, while others dig a more or less temporary hole in the ground
into which they carry their captured prey, and in which they take
refuge on the appearance of an enemy. The large wolf-spiders have
permanent burrows from which they do not wander far and in the mouths
of which they spend most of their time, on the look out for passing
insects.
Let us first catch one of the small wolf-spiders and examine it.
This is not a very simple operation with creatures which can run so
swiftly, but after a few attempts we induce a specimen to run up
into a glass tube held in the line of its course. We see it to be a
long-bodied spider thickly beset with hairs which entirely hide the
integument of the abdomen. Its general hue will probably be a dark
grey, and its abdomen will be decorated by a more or less distinct
pattern due, not as in the garden spider to pigments in the skin, but
to the coloration of the hairs. But look particularly at its eyes. A
pocket-lens will suffice to reveal that two of them are much larger
and much more business-like in appearance than anything _Epeira_
had to show. These are directed forwards, being placed at the upper
angles of the perpendicular front face, so to speak, of the animal.
Below them, just above the jaws, are four small eyes in a transverse
row, and behind them at some distance, on the upper surface of the
cephalothorax, are yet another pair of moderate size. In some groups
of spiders the eyes are not only small but have an indefinite, dull,
ineffectual appearance; here they are clear-cut, glossy and convex;
sight apparently counts for something in the case of the Lycosidae.
And this is what we should expect. A sedentary spider is informed
of the whereabouts of its prey by the sense of touch, through the
trembling of the web, but a wolf-spider spins no web and is dependent
on the keenness of its vision.
There is a very prettily marked English Lycosid which is often found on
sandhills, in situations particularly convenient for observation. Its
name is _Lycosa picta_, and it is incidentally interesting as affording
a good example of protective coloration, for the sandhill variety is
light-coloured and very inconspicuous when stationary on the sand,
while an inland variety not uncommon on the dark soil of heaths is of
a much darker hue. Carefully scrutinising the firmer sand of the dunes
on a sunny June day, I detect a number of small holes—the burrows of a
colony of these spiders—and approaching cautiously I establish myself
at full length at a distance of a yard or so on the side away from the
sun, in such an attitude that I can observe closely for a considerable
time without too much discomfort. The minutes pass and nothing
happens, but I know that the cardinal virtue of the naturalist is
patience, and I wait. Presently the dark circle of one of the burrows
is obliterated—it is filled by the sand-coloured head of the spider,
coming up to prospect. Other heads appear, and soon one spider, bolder
than the rest, emerges bodily, and remains for a minute motionless, on
the _qui vive_. Finding no cause for alarm, it presently begins moving
about stealthily, and before long several members of the colony are
busily exploring the neighbourhood. A cloud passes over the sun and all
quickly disappear into their holes, but this time without alarm, for
they come forth unhesitatingly when the sun shines again.
It is a fascinating sight to observe these little creatures pursuing
their operations in absolute silence under my very eyes. A few stealthy
steps are taken, the body being so moved that the battery of eyes is
brought to bear upon different points of the compass; a short quick run
ensues, followed by more cautious movements. I am not fortunate enough
to see the actual running down of a quarry, but in time I note one of
the colony bringing home an insect in its jaws. So absorbed am I that I
fairly jump when a horrified human voice close at hand observes “He’s
in a fit”! I have excited the solicitude of a girls’ school which has
approached noiselessly over the sand on their afternoon promenade, and
stands gazing at me with as much fascination as I at the spiders. I
hasten to reassure them, but the spell is broken, and the séance is at
an end. Not a spider is visible.
But I can still do one thing. Here is a good opportunity of finding
out something about the burrows of these spiders. In turf the
investigation would be difficult, but it is easy to operate in the
tolerably firm sand where the colony has established itself.
I insert a straw into one of the burrows as a guide to the exploration,
and with a knife carefully begin to remove the sand immediately round
it. It is lined, I find, by a very delicate and slight coating of silk,
no more than sufficient to keep the sand particles of its walls from
falling down into the tube. I go down for an inch and a half or so and
find that the tube ends blindly in a sort of silk-lined pocket, but
no spider is there! This is mysterious, for I am pretty sure that my
spiders are at home.
I go to work upon another burrow, but this time in a different way,
digging it out bodily with its surrounding sand, and placing it on
a sheet of paper, with which I am luckily provided, for a detailed
examination. I can now approach it from the side, and by carefully
removing the sand, lay bare the whole silken tube. As before there is a
straight perpendicular burrow, ending blindly, and uninhabited, but at
a point at about half-way down the tube I find a branch bending upward,
so that the whole tunnel is +Y+ shaped, and at the blind end of
this branch I find the spider.
This observation suggests that the tunnels of some of our English
wolf-spiders may be more complex than was imagined. At present nothing
is known of their nature in the case of other species.
A little later in the summer the appearance of a troop of wolf-spiders
has undergone a marked change; almost every individual will be found
burdened with a circular bag of eggs attached firmly to its spinnerets,
and carried about with it in all its wanderings.
[Illustration: Fig. 7. Wolf-spiders; _A_, with egg-cocoons; _B_, with
young on its back.]
The “cocoon” is worth examination. It is a rather flattened sphere,
with an equatorial line round it, giving the effect of two halves—an
upper and a lower. The operation of making it has very seldom been
observed, because it takes place in a closed retreat constructed for
the purpose. McCook was fortunate enough to see something of it in the
case of a captive _Lycosa_ which he kept in a glass jar partly filled
with soil. Luckily the spider dug its tunnel for cocooning purposes up
against the side of the jar, so that its interior was visible. It was
about an inch deep and fairly wide, and its aperture was closed with
silk.
Against the perpendicular wall of soil a circular silken cushion about
three quarters of an inch in diameter was spun, and the eggs deposited
in the centre. The edges of the cushion were then gathered up and
pulled over the eggs, and the bag thus formed was finished off with an
external layer of spinning work on the two halves of the sphere, the
seam or “equator” being left thin for the exit of the young spiders.
The _Lycosa_ then attached the cocoon to its spinnerets and proceeded
to bite away the silken sheet which sealed the burrow. The whole
operation lasted about four and a half hours.
Thenceforward, till the young are hatched, the wolf-spider never quits
her egg-bag, which she carries about on all her expeditions attached by
threads to the spinnerets. Garden-spiders die soon after laying their
eggs and never see their progeny, but here we have a case of maternal
solicitude persisting for many days, and the Peckhams seized upon it as
a good subject for investigating the subject of the memory of spiders.
If the cocoon were removed from the spinnerets, after how long an
interval would it be recognised by the mother?
A _Pirata_ was selected for experiment. It offered great resistance
to the removal of the cocoon, seizing it with its jaws and trying to
escape with it. When it had been taken away the mother displayed great
uneasiness, searching for it in all directions. It was returned to her
after an hour and a half, when she received it eagerly and immediately
attached it in the usual position.
From three others of the same species the cocoons were removed and
restored after thirteen, fourteen and a half, and sixteen hours
respectively. All remembered them and took them back immediately. But
twenty-four hours seemed to be the extreme limit of their memory;
after that interval two of the mothers refused to have anything to
do with their cocoons, while the third only resumed hers, slowly and
without any enthusiasm, after it had been placed before her seven
times in succession. Some other species seemed to possess a rather
longer memory, but the experimenters found no Lycosid constant in her
affection for so long a period as forty-eight hours.
We have said that Lycosid spiders see comparatively well; yet, if
they are placed within an inch or two of their cocoons they may be
quite a long time finding them. This is very puzzling until it is
considered that its habitual position is such that the spider never
sees it. She never has seen it since its construction, and does not
in the least recognise it by sight. Spiders of other groups, where
the female remains near but detached from the cocoon, are not at the
same disadvantage, and if the cocoon is removed to a short distance
the mother will go straight to it and bring it back. The wolf-spider
only knows the _feel_ of the cocoon; she may pass close by it without
recognition, but as soon as she touches it the cocoon is immediately
resumed—if the interval of separation has not been too great.
But is it necessary to restore to the spider her own cocoon? Will not
that of another spider serve as well? Certainly it will; a wolf-spider
will eagerly adopt the cocoon of a spider even belonging to a different
genus, if not greatly unlike her own in size. Nay, even a ball of pith
of the same size will be attached with alacrity to the spinnerets,
though if offered a choice between a cocoon and a pith ball the
spider, after some hesitation, selects the real article. One spider
even accepted a cocoon into which a leaden shot had been inserted,
making it many times its original weight. She could hardly crawl with
her new burden, but stuck to it gallantly, and when several efforts
to secure it to her spinnerets had proved ineffectual she carried
it about between her jaws and the third pair of legs. Again we find
the intelligence of the spider distinctly limited, but its powerful
instincts are equal to all ordinary requirements. Nature does not,
as a rule, play extravagant pranks, such as interchanging cocoons or
substituting for them pith balls and leaden pellets.
The famous Tarantula is a wolf-spider, though in America,
unfortunately, the name has been quite wrongly applied to the members
of an entirely different group. Everyone has heard of its deadly
repute, and of the myth that its bite can only be cured by the wild
tarantula dance or tarantella. It is one of the large Lycosids of
southern Europe. These, as we have said, are much less nomadic than
the smaller species, but have a permanent home, from which they do not
wander far afield. They prefer waste, arid places, and their burrows
are simple cylindrical tubes with the upper portion lined by silk, the
mouth being often surmounted by a sort of rampart of particles of soil
mingled with small pieces of wood collected in the neighbourhood. The
spider lurks in the mouth of the tube where its glistening eyes can be
distinctly seen. If an insect ventures near it rushes out and secures
it; if alarmed, it retreats instantly to the bottom of the burrow.
That most fascinating of all entomological writers, J. H. Fabre, made
some observations on a tarantula of southern France which well deserve
attention. Colonies of the spider were numerous in his neighbourhood,
and he set himself to procure some specimens. Old writers assert that
if a straw be inserted into the burrow the spider will seize it and
hold it so firmly that it may be drawn forth. Fabre found this method
exciting, but uncertain in its results. Another plan which had been
advocated was to approach warily and cut off the retreat of a spider by
plunging the blade of a knife into the soil below it and so cutting off
its retreat, but this required very rapid action, and was, moreover,
apt to be prevented by the presence of stones in the soil. He devised
a new scheme. He provided himself with a number of “bumble” bees in
narrow glass tubes—about the width of the spider burrows. Repairing
to a tarantula colony he would present the open end of the tube to
the mouth of a burrow. The liberated bee, seeing a hole in the ground
exactly suitable for its own purposes, would enter it with very little
hesitation. There would be a loud buzz and then instant silence.
Inserting a pair of forceps into the hole, Fabre would then withdraw
the bee with the spider clinging tenaciously to it. In all cases the
death of the bee was instantaneous, though the closest examination of
its dead body revealed no wound.
Now Fabre was fresh from his wonderful studies of the habits of the
solitary wasps, which provide their young with insects stung in such
a way as to cause paralysis but not death. In their case the problem
was to secure food for their larvae which should remain fresh for
many days, an instinct taught them to solve it in the most remarkable
manner. The problem of the spider was different. It was a case of
killing instantly, or being killed; a merely wounded bee is as
formidable as one unharmed. What Fabre desired to know was this: did
the spider trust to one invariable deadly stroke in dealing with the
bee, as the solitary wasp, according to its species, had been found to
act always precisely in the same way in paralysing its victim?
To settle this point the spider must be seen at work, and the obvious
plan seemed to be to enclose a bee and a tarantula in a glass
vessel and see what would happen. But nothing happened at all. The
spider, away from its burrow, refused to attack. The equally matched
antagonists treated each other with the greatest respect and only
evinced a desire to keep as far apart as possible. Even when placed in
the same tube both acted on the defensive, and no light was thrown on
the problem.
But Fabre’s ingenuity was equal to the occasion. It occurred to
him that to use as a bait an insect of burrowing habits had been a
tactical error; if instead of a bumble bee some other insect, equally
formidable, but not attracted by holes in the ground, were selected for
the purpose, the spider might be induced to rush forth and reveal its
method of attack.
A large carpenter bee—_Xylocopa_—was chosen and the mouth of
the tube containing it was presented as before to the mouth of the
tarantula tunnel. The insect showed no disposition to enter the tunnel,
but buzzed in the tube outside. Many burrows were tested before any
luck attended the investigator, but at length a spider responded.
There was a fierce rush, a clinch, and the bee was dead; the operation
was too rapid to follow, but the spider’s fangs remained where they
had struck—embedded just behind the insect’s neck. The experiment
was repeated until sufficient cases had been witnessed to establish
the fact that the tarantula dealt no random stroke but with unerring
precision and lightning rapidity plunged its fangs into the vital spot.
Fabre quaintly exclaims “J’étais ravi de ce savoir assassin; j’étais
dédommagé de mon épiderme rôti au soleil!”
Examples of the same species of tarantula kept in captivity threw
further light of the habits of the group. These large Lycosids live for
years, and though stay-at-homes when _rangé_ so-to-speak, they are at
first wanderers on the face of the earth. They do not settle down and
burrow till the autumn just after they have attained maturity. These
young adults are only about half the size they will eventually attain,
but the burrows are enlarged at need, so that it is customary to find
tubes of two sizes—those of the newly established small females, and
those of the fully-grown females of two or more years old.
Curiously enough, if disturbed, they entirely decline to burrow
unless it be the proper season for that operation, but remain inert
and helpless on the surface till they die. If, however, a tunnel is
provided for them, they enter it at once and adapt it to their needs.
The legs take no part in the burrowing process, which is entirely
carried out by the jaws. With infinite labour small particles of
earth are dislodged and carried by the mandibles to be dropped at a
considerable distance from the nest.
The parapet round the mouth of the tube is in nature usually quite
a small erection, but this seems to be due to the fact that only
a small amount of suitable material is available in the immediate
neighbourhood, and the spiders will not go far afield. In captivity,
when abundance of material was supplied, they attained a height of two
inches. Small stones, sticks, and strands of wool cut into lengths of
one inch and of various colours were placed within reach, and all were
used in building the parapet. Comparatively huge pebbles were rolled up
for a foundation, and fragments of earth and pieces of wool entirely
irrespective of colour were bound together by irregular spinning work.
On sunny days the spiders would crouch behind the parapet with their
eyes above its level. To distant insects they paid no attention, but
if one approached within leaping distance, it was pounced upon with
unfailing accuracy.
In due season the captives laid their eggs and enclosed them in the
regulation cocoon which they attached to their spinnerets, never
parting from them thenceforward, though considerably hampered by them
in their movements up and down the tube. But a very remarkable change
now took place in their behaviour at the mouth of the tunnel. In sunny
weather, instead of remaining, as Fabre puts it, “_accoudé_” on the
parapet, they reversed their position, raised their egg-cocoons with
their hind legs, and slowly and deliberately turned them about, so that
every part in succession should be exposed to the sun’s rays.
We now come to a remarkable habit possessed by all the Lycosidae.
When the young are ready to leave the cocoon they find an exit at
the thinner equatorial seam, and proceed immediately to climb on to
the back of the mother, clinging firmly to her covering of hairs.
If a wanderer, she carries them thus on all her expeditions; if a
stay-at-home, they accompany her up and down her tube. They are often
dislodged—indeed, when alarmed, they scatter for the moment, but when
the peril has passed they immediately swarm up the maternal legs to
their former position.
Now in the case of the tarantula, it is seven months before they are
able to fend for themselves. Meanwhile they eat nothing, and look on
with indifference while their mother feeds. She not only carries them
willingly, but exhibits solicitude when deprived of them, but she shows
no discrimination as to her own offspring, and is quite content with
those of another spider. The young, when brushed off, climb the legs
of the nearest female, and a spider may thus be laden with thrice her
proper load without any protest. They form a layer two or three deep,
and can then only find room by covering the whole of her back. They
nevertheless take care not to obscure her vision by covering her eyes.
Two mother tarantulas, each with her young on her back, came into
contact, and a battle _à outrance_ took place. One was slain, but the
double brood, scattered by the conflict, on its cessation climbed on
to the back of the victor, and remained calmly in position while she
proceeded to dine in leisurely fashion on the vanquished!
In March, seven months after hatching, the young were ready to
start life for themselves. Their first action was to climb to the
highest points attainable, whence they set sail in the manner already
described, and were borne gently away in the air.
We can hardly leave the tarantula without saying something on the
vexed question of spider venom. All over the world there are certain
particular spiders whose bite is especially feared. Among them are
the “Tarantula” and the “Malmignate” of southern Europe, the “Vancoho”
of Madagascar, the “Katipo” of New Zealand, and the “Queue rouge”
of the West Indies. Quite an extensive literature has arisen around
the subject but its perusal leaves one not much wiser than one was
before. Circumstantial accounts of deaths from the bite of a spider
are countered by the assertions of experimenters that they have
allowed themselves to be bitten repeatedly by the same species without
suffering any inconvenience. There is at all events some basis for
the popular view in the fact that all spiders possess a poison gland
which is analogous to that of the snake inasmuch as it opens near the
tip of the fang which is plunged into the animal attacked. In the case
of the large, powerful spiders of the family Mygalidae, and perhaps
in the tarantulas the effects of the bite on higher animals are not
negligible, and clearly exceed the results of a mere puncture. A young
sparrow and a mole bitten by Fabre’s tarantula in spots by no means
vital died within a few hours. But it is a very remarkable fact that
many of the most dreaded spiders are neither large nor powerful. The
“Malmignate,” the “Vancoho,” the “Katipo,” and the “Queue rouge” are
all members of the comparatively weak-jawed Theridiidae, and their only
striking characteristic is vivid coloration, all being marked with
red spots. It is probable that their deadly powers are almost entirely
fabulous; and that they have been singled out as particularly dangerous
merely because of their conspicuous appearance.
The smaller species are certainly harmless as far as man is concerned,
and it is even disputed whether their poison plays much part in
the ordinary slaying of insects. The very inconsistent results of
experiments may be due to some control exercised by the spider over the
output of poison. There is no proof that its ejection is automatic,
and it is quite possible that the spider is economical in its use. Or
again, in some of the cases of innocuous biting, the supply of venom
may have run short.