Fig. 4. Young spider preparing for an aerial voyage.Fig. 4. Young spider preparing for an aerial voyage.
Fig. 4. Young spider preparing for an aerial voyage.
This, then, is the habitual method by which newbroods of spiders distribute themselves, especially the sedentary kinds which would otherwise soon become over crowded in the neighbourhood of the parent nest. And we really need not have sought out a railing at all except for its very great convenience of observation. The same thing is going on everywhere. It largely accounts for the astonishing carpet of silk that the dew reveals to us on lawns and meadows at such times of the year. Young spiders have been busy from early dawn crawling over the grass, climbing the higher blades, and setting sail, and the whole field is covered with their lines. Railings come in handy as furnishing an elevatedstarting point, but any shrub or bush will do, and young spiders have been seen setting sail from the parent web itself.
McCook has given some interesting notes of his own observations on aeronautic spiders. He followed an Attid spider fifty feet till it was carried upward out of sight in a current of air. A Lycosid disappeared in the same way after being followed—at a run—for a hundred feet. The largest Epeirid he ever saw taking flight was “the size of a marrowfat pea, say one-fourth of an inch long. After having floated over a field and above a hedge-row, it crossed a road and anchored upon the top of a young tree.” But perhaps his most interesting observation was on the ability of spiders to control in some measure the duration of their flight by reefing their sails if they wish to descend, for he saw a ballooning spider collecting some of the streamers into a ball of silk which accumulated near its mouth as it gradually sank to earth.
The phenomenon known as “gossamer” has puzzled people for centuries, and English poetical literature is full of allusions to it. Chaucer classes it with “ebbe and floud” as an unsolved riddle, and Spenser, Quarles and Thomson all make mention of it, generally embodying the popular belief that it somehow had its origin in dew. “Scorchèd deaw” Spenser calls it, while Thomson’s expression is “dewevaporate.” The phenomenon in question is the occasional appearance of vast numbers of silken flakes which fill the air, and which in some recorded instances extend over many square miles and to a height of several hundred feet. Our observations will have given a clue to its origin which is entirely attributable to spiders, and in large measure to their ballooning habit, though no doubt reinforced by a large quantity of silk spun for other purposes and caught up into the air by the breeze. For a vivid account of such a shower the reader is referred to Letter LXV of White’sNatural History of Selborne, and Darwin in hisNaturalist’s Voyage(Chap. VIII) records a case of the “gossamer spider” descending in multitudes on the “Beagle” when sixty miles from land.
In the ballooning habit we have the probable explanation of the wide distribution of certain species of spiders which seem at first exceedingly ill adapted for covering large distances. The Huntsman Spider,Heteropoda venatorius, is practically cosmopolitan in tropical and sub-tropical regions and the usual view has been that ships have conveyed it from port to port. McCook, however, gives several reasons for believing that the trade winds have much more to do with the matter, and this may well be the case, though both agencies have doubtless been at work.
Very likely it was not obvious to the reader why he was recommended to select a particularly calm, sunny autumn day for his study of spider aeronautics; a strong steady breeze might well appear more suitable for the purpose. Yet he would find these operations at a standstill on a windy day, and the best possible conditions are a still warm morning after a spell of cooler weather. The lightest air-currents serve to float the delicate silken threads, and, what is more important, the increase of temperature causes an upward draught which rapidly carries the spider to a useful height where it sails gently away instead of being swept roughly over the surface of the ground.
AGELENA
Beforegoing 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 takethe 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.
NowAgelenadoes 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 evincegreat 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 withAgelenathe 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 withAgelena, 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 hisnight’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 oneAgelena.
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.
Fig. 5. Agelena weaving her egg-cocoon.Fig. 5.Agelenaweaving her egg-cocoon.
Fig. 5.Agelenaweaving 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 againstit. 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 eggsupwards, against this loose-textured silk, aiding the egg-mass to adhere byoccasional 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 anyreader 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.
WATER-SPIDERS
Hereis the place to insert a short account of some near relations ofAgelenawhich we shall certainly not meet in our walk, but of which the mode of life is too interesting to be altogether passed over in silence.
We have seen that the class Crustacea (crabs, shrimps, etc.) is the great division of the Arthropoda entirely adapted to an aquatic life, breathing, by means of gills, the air which is dissolved in the water. Insects and spiders are air-breathing, and properly belong to the land; yet there are many insects which pass their early stages—often the greater portion of their life—in the water, and some which are very fairly at home there when adult. Such insects often have gills when young, and are therefore at that period true water animals, like the Crustacea.
The Arachnida—that division of the Arthropoda to which the spiders belong—include a few groups which permanently inhabit the sea, and could not live on land. There are even some weird creatures called Sea-spiders (Pycnogonids), but these do not concern us, for they are very far removed from the true spiders which are the subject of our investigations.
Now the true spiders are always air-breathing, and if they venture into the water at all they must frequently come up to the surface to breathe, or else they must store up a reservoir of air beneath the surface of the water if they are to avoid death by drowning. Nevertheless some of them have been hardy enough to encroach on the domain of the Crustacea. Not a few are able to run freely on the surface of the water and even to dive occasionally for the purpose of seizing one of its denizens, but the number of those which have succeeded in really adapting themselves to aquatic life is very limited, and is, as far as we know, restricted to two small groups, both of them members of the Agelenidae.
Among the coral reefs of the Indian and Pacific oceans, and also off the southern coast of Africa there are found spiders of the genusDesiswhich spend almost all their time under the surface of the sea, from which they only emerge at low tide. They construct very closely woven tents, impermeable to sea-water, which imprison air at low tide, generally choosing for the purpose some cavity which has been excavated by one of the burrowing molluscs. Beyond this we really know very little about them, and there is much difference of opinion as to the mode in which they obtain their food. Some writers state that they only leave their shelters at low tide to chase small crustaceans, and that when placed in vessels containingsea water they are quite helpless and soon drown. On the other hand one observer found that a species ofDesiswas quite at home in a sea-water tank, in which it swam freely and even attacked and fed upon a small fish. Possibly different species of the genus behave in different ways, some being more truly aquatic than others, though it is certain that the troubled waters of a coral sea are not a very promising field for sub-aqueous operations. We know a great deal more of the mode of life of those Agelenids which have taken to living in fresh water. Indeed the subject of the water-spider,Argyroneta aquatica, is so hackneyed that in dealing with it we shall probably be telling the reader much of what he knows already, but that possibility must be risked.
There is, then, in many of our lakes, ponds and slow-flowing rivers with a weedy bed, a spider which has entirely taken to a water life, and for which it is useless to search on land. It is a docile captive, and consequently a favourite subject for transference to an aquarium, where its habits can be observed at leisure. Its first care is to construct beneath the water a small dome-shaped web, open below, and it generally selects the under surface of the leaf of a water weed for the purpose of anchorage, though a ready-made shelter is often furnished by the empty shell of some fresh-water mollusc. Its next proceeding is to fill this retreat with air in a very ingenious manner.
While swimming about in the water the spider has a most striking appearance, its abdomen almost resembling a globe of quicksilver. This is because the body is enveloped in a bubble of air, retained largely by the long hairs with which it is clothed. Thus it carries its atmosphere about with it, and as often as not it swims with its back downwards, which has the effect of bringing the bulk of the air-bubble towards its ventral surface, where the breathing pores are situated. Now when the dome-shaped web is ready to be filled with air the spider rises to the surface, lifts its abdomen above it, and brings it down with a flop, thus imprisoning an extra large air-bubble which it embraces with its hind-legs by way of holding it more securely, and then, swimming rapidly down by means of its other legs to the web it discharges its load of air beneath the downwardly directed mouth of the dome.
By a frequent repetition of this process the dome is at length filled and converted into a veritable diving-bell, in which the spider can exist quite comfortably until the supply of oxygen in the imprisoned air is exhausted and has to be renewed. From this base it issues forth to feed upon fresh-water insects and crustaceans, sometimes even attacking small fishes.
The proceedings of the maleArgyronetain the mating season are very curious. He seeks out thetent of a female and sets up his own establishment—generally somewhat smaller—close at hand, filling it with air in the approved manner. He then builds a sort of corridor uniting the two domes, and when this is complete he bites through the female dome, thus uniting the two air reservoirs by means of a connecting tube. Not seldom it happens that the female is in no mood for dalliance, and a battle royal ensues, with disastrous results to both domiciles and the tube that connects them. The male, however, is in this case well able to hold his own, for he is larger than the female, a phenomenon elsewhere unknown in the spider realm.Argyronetalives for some years, and makes two diving-bells each year—one near the surface in summer and one at a greater depth in winter. It was thought at first that one was constructed especially for receiving the eggs and the other as a habitation, but the egg-cocoon may be found in either, for there are two broods in the course of the year. The winter dome is of very dense silk, glossy in appearance, and giving the effect of a uniform sheet of silky material rather than a fabric. Moreover its mouth is closed, and the spider remains inactive within. It is this winter domicile that is most frequently found in the shells of molluscs. The egg-cocoon is also dome-shaped, having a convex upper and a flat under surface. The newly hatched young inhabit their mother’s tent for a time and thenset forth in the water to seek their living and set up establishments on their own account.
There is only one known species ofArgyroneta, widely distributed in the temperate regions of Europe and Asia. The female is about half-an-inch long, of no particular beauty out of the water, its colour being reddish-brown, and its body and legs very hairy. There are, however, a few New Zealand spiders rather closely allied to it and of very similar habits.
CRAB-SPIDERS. MIMICRY
Allspiders can spin, but by no means all use that power to entrap their prey. Many have no settled abode or resting place except perhaps for a short time when they are rearing their young. Among these roving tribes, there are three groups which may engage our attention for a time—the Crab-spiders (Thomisidae), the Wolf-spiders (Lycosidae) and the Jumping spiders (Attidae).
Crab-spiders are seldom seen by the ordinary observer, for their habits do not bring them prominently into notice, and many of them are of small size. They are well named, for there is something exceedingly crab-like in their appearance andin their actions. Their body is generally broad and flattened, and their legs, instead of being arranged fore and aft, like those of most spiders, extend more or less laterally, and though they can move pretty actively in any direction their normal method of progression is sideways. Then again, when frightened they cramp their legs up under their bodies in a most crab-like fashion and “sham dead.”
Fig. 6. A Crab-spider.Fig. 6. A Crab-spider (Thomisidae), × 3.
Fig. 6. A Crab-spider (Thomisidae), × 3.
We saw some of these spiders on the iron railing, but their real haunts are among grass and herbage or upon the trunks of trees. Some are true rovers, hunting their prey by day and camping out wherever they happen to find themselves at night. Their methods are without guile—except that they approach their victims warily; their trust is in rapidity ofaction and superior strength. But other crab-spiders lead a less strenuous life; their habit is to lurk in moss, lichen, or flowers till an insect draws near enough to be seized without any great expenditure of energy.
Now in the case of some of these spiders the chance of obtaining a meal is very greatly increased by a remarkable similarity of coloration between the spider and its usual hunting ground. The spider’s object is to remain invisible, and concealment is obviously more easy if its colour matches that of its environment. To a greater or less extent this protective coloration as it is called prevails universally:—spiders are seldom conspicuous objects among their usual surroundings, but it is only occasionally that we meet with cases of very remarkable colour adaptation. Two such, however, occur among English crab-spiders. One is a species not uncommon in the south of England, and fairly plentiful in the New Forest, where it is to be sought among the lichen on the tree trunks, where its blue-grey body, marked with black and white blotches makes it practically invisible except when in motion. It rejoices in the name ofPhilodromus margaritatus. The other case is that of the spider known asMisumena vatia, which is variable in colour, some specimens being yellow and others pink, while a variety of the species has a blood-red streak decorating the front part of its abdomen. If it wereto choose lichen as a hunting ground there would be little chance of concealment, but it does nothing so foolish:—it hides among the petals of flowers, generally, but not always, among flowers more or less of its own colour.
Now this phenomenon of resemblance is sometimes carried very much farther than a tolerable correspondence between the colour of an animal and its surroundings; it occasionally amounts to an apparent imitation, in form and in behaviour as well as in colour, of some other object, either animal or vegetable and in such cases we have examples of what is known as Mimicry. Most people have seen remarkable instances of this phenomenon in the “stick” and “leaf” insects of entomological collections. There are several different ways in which such a resemblance may be profitable to the imitator. Clearly it may be advantageous for a weak animal to be mistaken for one much more formidable and less likely to be attacked, or for an insect which is really extremely good eating to resemble closely one which birds well know to be unpalatable. Or again, if your line is to lieperduand wait for some unwary insect to come within reach, it must be a distinct asset to be indistinguishable from such an innocent object as a twig or a leaf; and the same disguise may serve you if you are the possible victim and you can make the would-be devourer believe that you are a mere vegetable.
It is seldom difficult to see some such possibility of gain in the numerous well-known cases of insect mimicry. The wasp tribe—formidable with their stings—are often “mimicked”; the unpalatable Heliconid butterflies are “imitated” by members of edible families, and some insects are such exact imitations of leaves that the all-devouring army ants have been seen to run over them without discovering the imposition.
“Mimicry” is an unfortunate term inasmuch as it seems to imply intentional imitation; “protective resemblance” is better. It is generally accounted for by the action of “natural selection” upon random variations. No two members of a brood are exactly alike; slight variations in form, size, colour, etc., are constantly occurring, and when the variation is a useful one the animal possessing it has a slightly better chance of surviving and rearing progeny, some of whom will probably possess the same peculiarity, perhaps even in a more marked degree, and will be better equipped than their neighbours in the struggle for life. The happy possessors of such favourable variations are thus in a sense “selected” by nature, and this selection, acting through countless generations, is thought to be the chief agent in bringing about the remarkable phenomenon of protective resemblance.
The theory has, no doubt, been pushed too far;fanciful resemblances have been detected and advantages of which there is no proof are sometimes asserted, and moreover other possible ways of accounting for the facts have been too much overlooked.
But however it has come about, there is a case of “mimicry” among crab-spiders which deserves more than a passing mention. The name of the spider in question isPhrynarachne decipiens, and it was accidentally discovered by Forbes when butterfly-hunting in Java. It spins a white patch of silk on the upper side of a leaf on which it places itself back-downwards, clinging to the web by means of spines on its legs. It then folds its legs closely and lies absolutely still. In this position the spider and web look precisely like the dropping of some bird upon the leaf; such droppings are frequently seen, and seem to be particularly attractive to butterflies. It was not until Forbes tried to catch a butterfly settled on a leaf that he found that what looked like excrement was really a spider which held the butterfly in its grasp. Even after this experience he was again deceived by the same species in Sumatra.
There are several extremely ant-like spiders, and it is remarkable that some of the imitators belong to widely different spider families:—that is to say the resemblance has arisen independently from quite different starting points.
It is very noteworthy that resemblance in structure is always accompanied by similarity of behaviour—as indeed it is bound to be if any benefit is to accrue to the mimic. Your resemblance to a leaf will deceive no one if you run wildly about, and your imitation of an ant will lack verisimilitude if you adopt a slow and stately method of progression. Ant-like spiders adopt the hurried and apparently undecided gait of their models, and insects which look like sticks, leaves, or inanimate objects all possess the power—and the habit—of remaining for a long time perfectly motionless.
WOLF-SPIDERS
Ofthe 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 thename 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 namedPirata, 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 ofan 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 anythingEpeirahad 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; sightapparently 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 isLycosa 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 thequi 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 investigationwould 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 isYshaped, 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.
Fig. 7. Wolf-spiders.Fig. 7. Wolf-spiders;A, with egg-cocoons;B, with young on its back.
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 caseof a captiveLycosawhich 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. TheLycosathen 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?
APiratawas 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 sinceits 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 thefeelof 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 ordinaryrequirements. 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 beinserted 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 shouldremain 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 chosenand 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 whenrangéso-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 oneapproached 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 sevenmonths 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 battleà outrancetook 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 spiderswhose 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.
JUMPING SPIDERS
Weare not in the land of the jumping spiders or Attidae, and our few and sober-coloured examples of the group give but a feeble idea of the Attid fauna of tropical countries where these creatures abound and often rival the “ruby-tail” flies in the brilliancy of their hues.