Chapter XVIII Structures of Spiders
Modern naturalists do not rank spiders among insects, because they have no antennæ, and no division between the head and the shoulders. They breathe by leaf-shaped gills, situated under the belly, instead of spiracles in the sides; have a heart connected with these; have eight legs instead of six; and eight fixed eyes. But as spiders are popularly considered insects, it will sufficiently suit our purpose to introduce them here as such.
The apparatus by which spiders construct their ingenious fabrics is much more complicated than that which we have described as common to the various species of caterpillars. Caterpillars have only two reservoirs for the materials of their silk; but spiders, according to the dissections of M. Treviranus, have four principal vessels, two larger and two smaller, with a number of minute ones at their base. Several small tubes branch towards the reservoirs, for carrying to them, no doubt, a supply of the secreted material. Swammerdam describes them as twisted into many coils of an agate colour.EJ We do not find them coiled, but nearly straight, and of a deep-yellow colour. From these, when broken, threads can be drawn out like those spun by the spider, though we cannot draw them so fine by many degrees.
From these little flasks or bags of gum, situated near the apex of the abdomen, and not at the mouth, as in caterpillars, a tube originates, and terminates in the external spinnerets, which may be seen by the naked eye in the larger spiders, in the form of five little teats surrounded by a circle, as represented in the following figure.
We have seen that the silken thread of a caterpillar is composed of two united within the tube of the spinneret, but the spider’s thread would appear, from the first view of its five spinnerets, to be quintuple, and in some species which have six teats, so many times more. It is not safe, however, in our interpretations of nature to proceed upon conjecture, however plausible, nor to take anything for granted which we have not actually seen; since our inferences in such cases are almost certain to be erroneous. If Aristotle, for example, had ever looked narrowly at a spider when spinning, he could not have fancied, as he does, that the materials which it uses are nothing but wool stripped from its body. On looking, then, with a strong magnifying glass, at the teat-shaped spinnerets of a spider, we perceive them studded with regular rows of minute bristle-like points, about a thousand to each teat, making in all from five to six thousand. These are minute tubes which we may appropriately term spinnerules, as each is connected with the internal reservoirs, and emits a thread of inconceivable fineness. In the following figure, this wonderful apparatus is represented as it appears in the microscope.
We do not recollect that naturalists have ventured to assign any cause for this very remarkable multiplicity of the spinnerules of spiders, so different from the simple spinneret of caterpillars. To us it appears to be an admirable provision for their mode of life. Caterpillars neither require such strong materials, nor that their thread should dry as quickly. It is well known in our manufactures, particularly in rope-spinning, that in cords of equal thickness, those which are composed of many smaller ones united are greatly stronger than those which are spun at once. In the instance of the spider’s thread, this principle must hold still more strikingly, inasmuch as it is composed of fluid materials that require to be dried rapidly, and this drying must be greatly facilitated by exposing so many to the air separately before their union, which is effected at the distance of about a tenth of an inch from the spinnerets. In the following figure each of the threads represented is reckoned to contain one hundred minute threads, the whole forming only one of the spider’s common threads.
Leeuwenhoeck, in one of his extraordinary microscopical observations on a young spider not bigger than a grain of sand, upon enumerating the threadlets in one of its threads, calculated that it would require four millions of them to be as thick as a hair of his beard.
Another important advantage derived by the spider from the multiplicity of its threadlets is, that the thread affords a much more secure attachment to a wall, a branch of a tree, or any other object, than if it were simple; for, upon pressing the spinneret against the object, as spiders always do when they fix a thread, the spinnerules are extended over an area of some diameter, from every hair’s-breadth of which a strand, as rope-makers term it, is extended to compound the main cord. The preceding figure exhibits this ingenious contrivance.
Those who may be curious to examine this contrivance will see it best when the line is attached to any black object, for the threads, being whitish, are, in other cases, not so easily perceived.
Shooting of the Lines.
It has long been considered a curious though a difficult investigation, to determine in what manner spiders, seeing that they are destitute of wings, transport themselves from tree to tree, across brooks, and frequently through the air itself, without any apparent starting point. On looking into the authors who have treated upon this subject, it is surprising how little there is to be met with that is new, even in the most recent. Their conclusions, or rather their conjectural opinions, are, however, worthy of notice; for by unlearning error, we the more firmly establish truth.
1. One of the earliest notions upon this subject is that of Blancanus, the commentator on Aristotle, which is partly adopted by Redi, by Henricus Regius of Utrecht, by Swammerdam, EK by Lehmann, and by Kirby and Spence.EL “The spider’s thread,” says Swammerdam, “is generally made up of two or more parts, and after descending by such a thread, it ascends by one only, and is thus enabled to waft itself from one height or tree to another, even across running waters; the thread it leaves loose behind it being driven about by the wind, and so fixed to some other body.” “I placed,” says Kirby, “the large garden spider (Epeira diadema) upon a stick about a foot long, set upright in a vessel containing water.… It let itself drop, not by a single thread, but by two, each distant from the other about the twelfth of an inch, guided, as usual, by one of its hind feet, and one apparently smaller than the other. When it had suffered itself to descend nearly to the surface of the water, it stopped short, and by some means, which I could not distinctly see, broke off, close to the spinners, the smallest thread, which still adhering by the other end to the top of the stick, floated in the air, and was so light as to be carried about by the slightest breath. On approaching a pencil to the loose end of this line, it did not adhere from mere contact. I therefore twisted it once or twice round the pencil, and then drew it tight. The spider, which had previously climbed to the top of the stick, immediately pulled at it with one of its feet, and finding it sufficiently tense, crept along it, strengthening it as it proceeded by another thread, and thus reached the pencil.”
We have repeatedly witnessed this occurrence, both in the fields and when spiders were placed for experiment, as Kirby has described; but we very much doubt that the thread broken is ever intended as a bridge cable, or that it would have been so used in that instance, had it not been artificially fixed and accidentally found again by the spider. According to our observations, a spider never abandons, for an instant, the thread which she despatches in quest of an attachment, but uniformly keeps trying it with her feet, in order to ascertain its success. We are, therefore, persuaded that when a thread is broken in the manner above described, it is because it has been spun too weak; and spiders may often be seen breaking such threads in the process of netting their webs. (J. R.)
The plan, besides, as explained by these distinguished writers, would more frequently prove abortive than successful, from the cut thread not being sufficiently long. They admit, indeed, that spiders’ lines are often found “a yard or two long, fastened to twigs of grass not a foot in height.… Here, therefore, some other process must have been used.”EM
2. Our celebrated English naturalist, Dr. Lister, whose treatise upon our native spiders has been the basis of every subsequent work on the subject, maintains that “some spiders shoot out their threads in the same manner that porcupines do their quills;EN that whereas the quills of the latter are entirely separated from their bodies, when thus shot out, the threads of the former remain fixed to their anus, as the sun’s rays to its body.”EO A French periodical writer goes a little farther, and says, that spiders have the power of shooting out threads, and directing them at pleasure towards a determined point, judging of the distance and position of the object by some sense of which we are ignorant.EP Kirby also says, that he once observed a small garden spider (Aranea reticulata) “standing midway on a long perpendicular fixed thread, and an appearance caught” his “eye, of what seemed to be the emission of threads.” “I, therefore,” he adds, “moved my arm in the direction in which they apparently proceeded, and, as I had suspected, a floating thread attached itself to my coat, along which the spider crept. As this was connected with the spinners of the spider, it could not have been formed” by breaking a “secondary thread.”EQ Again, in speaking of the gossamer-spider, he says, “it first extends its thigh, shank, and foot, into a right line, and then, elevating its abdomen till it becomes vertical, shoots its thread into the air, and flies off from its station.”ER
Another distinguished naturalist, Mr. White of Selborne, in speaking of the gossamer-spider, says, “Every day in fine weather in autumn do I see these spiders shooting out their webs, and mounting aloft: they will go off from the finger, if you will take them into your hand. Last summer, one alighted on my book as I was reading in the parlour; and running to the top of the page, and shooting out a web, took its departure from thence. But what I most wondered at was, that it went off with considerable velocity in a place where no air was stirring; and I am sure I did not assist it with my breath.”ES
Having so often witnessed the thread set afloat in the air by spiders, we can readily conceive the way in which those eminent naturalists were led to suppose it to be ejected by some animal force acting like a syringe; but as the statement can be completely disproved by experiment, we shall only at present ask, in the words of Swammerdam—“how can it be possible that a thread so fine and slender should be shot out with force enough to divide and pass through the air?—is it not rather probable that the air would stop its progress, and so entangle it and fit it to perplex the spider’s operations?”ET The opinion, indeed, is equally improbable with another, suggested by Dr. Lister, that the spider can retract her thread within the abdomen, after it has been emitted.EU De GeerEV very justly joins Swammerdam in rejecting both of these fancies, which, in our own earlier observations upon spiders, certainly struck us as plausible and true. There can be no doubt, indeed, that the animal has a voluntary power of permitting the material to escape, or stopping it at pleasure, but this power is not projectile.
3. “There are many people,” says the Abbé de la Pluche, “who believe that the spider flies when they see her pass from branch to branch, and even from one high tree to another; but she transports herself in this manner: she places herself upon the end of a branch, or some projecting body, and there fastens her thread; after which, with her two hind feet, she squeezes her dugs (spinnerets), and presses out one or more threads of two or three ells in length, which she leaves to float in the air till it be fixed to some particular place.”EW Without pretending to have observed this, Swammerdam says, “I can easily comprehend how spiders, without giving themselves any motion, may, by only compressing their spinnerets, force out a thread, which being driven by the wind, may serve to waft them from one place to another.”EX Others, proceeding upon a similar notion, give a rather different account of the matter. “The spider,” says Bingley, “fixes one end of a thread to the place where she stands, and then with her hind paws draws out several other threads from the nipples, which, being lengthened out and driven by the wind to some neighbouring tree or other object, are by their natural clamminess fixed to it.”EY
Observation gives some plausibility to the latter opinion, as the spider always actively uses her legs, though not to draw out the thread, but to ascertain whether it has caught upon any object. The notion of her pressing the spinneret with her feet must be a mere fancy; at least it is not countenanced by anything which we have observed.
4. An opinion much more recondite is mentioned, if it was not started, by M. D’Isjonval, that the floating of the spider’s thread is electrical. “Frogs, cats, and other animals,” he says, “are affected by natural electricity, and feel the change of weather; but no other animal more than myself and my spiders.” During wet and windy weather he accordingly found that they spun very short lines, “but when a spider spins a long thread, there is a certainty of fine weather for at least ten or twelve days afterwards.”EZ A periodical writer, who signs himself Carolan,FA fancies that in darting out her thread the spider emits a stream of air, or some subtle electric fluid, by which she guides it as if by magic.
A living writer (Mr. John Murray), whose learning and skill in conducting experiments give no little weight to his opinions, has carried these views considerably farther. “The aëronautic spider,” he says, “can propel its thread both horizontally and vertically, and at all relative angles, in motionless air, and in an atmosphere agitated by winds; nay more, the aërial traveller can even dart its thread, to use a nautical phrase, in the ‘wind’s eye.’ My opinion and observations are based on many hundred experiments.… The entire phenomena are electrical. When a thread is propelled in a vertical plane, it remains perpendicular to the horizontal plane, always upright, and when others are projected at angles more or less inclined, their direction is invariably preserved; the threads never intermingle, and when a pencil of threads is propelled, it ever presents the appearance of a divergent brush. These are electrical phenomena, and cannot be explained but on electrical principles.”
“In clear, fine weather, the air is invariably positive; and it is precisely in such weather that the aëronautic spider makes its ascent most easily and rapidly, whether it be in summer or in winter.” “When the air is weakly positive, the ascent of the spider will be difficult, and its altitude extremely limited, and the threads propelled will be but little elevated above the horizontal plane. When negative electricity prevails, as in cloudy weather, or on the approach of rain, and the index of De Saussure’s hygrometer rapidly advancing towards humidity, the spider is unable to ascend.”FB
Mr. Murray had previously told us, that “when a stick of excited sealing-wax is brought near the thread of suspension, it is evidently repelled; consequently, the electricity of the thread is of a negative character,” while “an excited glass tube brought near, seemed to attract the thread, and with it the aëronautic spider.”FC His friend, Mr. Bowman, further describes the aërial spider as “shooting out four or five, often six or eight, extremely fine webs several yards long, which waved in the breeze, diverging from each other like a pencil of rays.” One of them “had two distinct and widely-diverging fasciculi of webs,” and “a line uniting them would have been at right angles to the direction of the breeze.”FD
Such is the chief evidence in support of the electrical theory; but though we have tried these experiments, we have not succeeded in verifying any one of them. The following statements of Mr. Blackwall come nearer our own observations.
5. “Having procured a small branched twig,” says Mr. Blackwall, “I fixed it upright in an earthen vessel containing water, its base being immersed in the liquid, and upon it I placed several of the spiders which produce gossamer. Whenever the insects thus circumstanced were exposed to a current of air, either naturally or artificially produced, they directly turned the thorax towards the quarter whence it came, even when it was so slight as scarcely to be perceptible, and elevating the abdomen, they emitted from their spinners a small portion of glutinous matter, which was instantly carried out in a line, consisting of four finer ones, with a velocity equal, or nearly so, to that with which the air moved, as was apparent from observations made on the motion of detached lines similarly exposed. The spiders, in the next place, carefully ascertained whether their lines had become firmly attached to any object or not, by pulling at them with the first pair of legs; and if the result was satisfactory, after tightening them sufficiently, they made them pass to the twig; then discharging from their spinners, which they applied to the spot where they stood, a little more of their liquid gum, and committing themselves to these bridges of their own constructing, they passed over them in safety, drawing a second line after them, as a security in case the first gave way, and so effected their escape.
“Such was invariably the result when spiders were placed where the air was liable to be sensibly agitated: I resolved, therefore, to put a bell-glass over them; and in this situation they remained seventeen days, evidently unable to produce a single line by which they could quit the branch they occupied, without encountering the water at its base; though, on the removal of the glass, they regained their liberty with as much celerity as in the instances already recorded.
“This experiment, which, from want of due precaution, has misled so many distinguished naturalists, I have tried with several geometric spiders, and always with the same success.”FE
Mr. Blackwall, from subsequent experiments, says he is “confident in affirming, that in motionless air spiders have not the power of darting their threads even through the space of half an inch.”FF The following details are given in confirmation of this opinion. Mr. Blackwall observed, the 1st Oct., 1826, a little before noon, with the sun shining brightly, no wind stirring, and the thermometer in the shade ranging from 55°·5 to 64°, a profusion of shining lines crossing each other at every angle, forming a confused net-work, covering the fields and hedges, and thickly coating his feet and ankles, as he walked across a pasture. He was more struck with the phenomenon, because on the previous day a strong gale of wind had blown from the south, and as gossamer is only seen in calm weather, it must have been all produced within a very short time.
“What more particularly arrested my attention,” says Mr. Blackwall, “was the ascent of an amazing quantity of webs, of an irregular, complicated structure, resembling ravelled silk of the finest quality and clearest white; they were of various shapes and dimensions, some of the largest measuring upwards of a yard in length, and several inches in breadth in the widest part; while others were almost as broad as long, presenting an area of a few square inches only.
“These webs, it was quickly perceived, were not formed in the air, as is generally believed, but at the earth’s surface. The lines of which they were composed, being brought into contact by the mechanical action of gentle airs, adhered together, till, by continual additions, they were accumulated into flakes or masses of considerable magnitude, on which the ascending current, occasioned by the rarefaction of the air contiguous to the heated ground, acted with so much force as to separate them from the objects to which they were attached, raising them in the atmosphere to a perpendicular height of at least several hundred feet. I collected a number of these webs about mid-day, as they rose; and again in the afternoon, when the upward current had ceased, and they were falling; but scarcely one in twenty contained a spider: though, on minute inspection, I found small winged insects, chiefly aphides, entangled in most of them.
“From contemplating this unusual display of gossamer, my thoughts were naturally directed to the animals which produced it, and the countless myriads in which they swarmed almost created as much surprise as the singular occupation that engrossed them. Apparently actuated by the same impulse, all were intent upon traversing the regions of air: accordingly, after gaining the summits of various objects, as blades of grass, stubble, rails, gates, &c., by the slow and laborious process of climbing, they raised themselves still higher by straightening their limbs; and elevating the abdomen, by bringing it from the usual horizontal position into one almost perpendicular, they emitted from their spinning apparatus a small quantity of the glutinous secretion with which they construct their webs. This viscous substance being drawn out by the ascending current of rarefied air into fine lines several feet in length, was carried upward, until the spiders, feeling themselves acted upon with sufficient force in that direction, quitted their hold of the objects on which they stood, and commenced their journey by mounting aloft.
“Whenever the lines became inadequate to the purpose for which they were intended, by adhering to any fixed body, they were immediately detached from the spinners, and so converted into terrestrial gossamer, by means of the last pair of legs, and the proceedings just described were repeated; which plainly proves that these operations result from a strong desire felt by the insects to effect an ascent.”FG Mr. Blackwall has recently read a paper (still unpublished) in the Linnean Society, confirmatory of his opinions.
6. Without going into the particulars of what agrees or disagrees in the above experiments with our own observations, we shall give a brief account of what we have actually seen in our researches. (J. R.) So far as we have determined, then, all the various species of spiders, how different soever the form of their webs may be, proceed in the circumstance of shooting their lines precisely alike; but those which we have found the most manageable in experimenting, are the small gossamer spider (Aranea obtextrix, Bechstein), known by its shining blackish-brown body and reddish-brown semi-transparent legs; but particularly the long-bodied spider (Tetragnatha extensa, Latr.), which varies in colour from green to brownish or grey—but has always a black line along the belly, with a silvery white or yellowish one on each side. The latter is chiefly recommended by being a very industrious and persevering spinner, while its movements are easily seen, from the long cylindrical form of its body and the length of its legs.
We placed the above two species with five or six others, including the garden, the domestic and the labyrinthic spiders, in empty wine-glasses, set in tea-saucers filled with water to prevent their escape. When they discovered, by repeated descents from the brims of the glasses, that they were thus surrounded by a wet ditch, they all set themselves to the task of throwing their silken bridges across. For this purpose they first endeavoured to ascertain in what direction the wind blew, or rather (as the experiment was made in our study) which way any current of air set,—by elevating their arms as we have seen sailors do in a dead calm. But, as it may prove more interesting to keep to one individual, we shall first watch the proceedings of the gossamer spider.
Finding no current of air on any quarter of the brim of the glass, it seemed to give up all hopes of constructing its bridge of escape, and placed itself in the attitude of repose; but no sooner did we produce a stream of air, by blowing gently towards its position, than, fixing a thread to the glass, and laying hold of it with one of its feet, by way of security, it placed its body in a vertical position, with its spinnerets extended outwards; and immediately we had the pleasure of seeing a thread streaming out from them several feet in length, on which the little aëronaut sprung up into the air. We were convinced, from what we thus observed, that it was the double or bend of the thread which was blown into the air; and we assigned as a reason for her previously attaching and drawing out a thread from the glass, the wish to give the wind a point d’appui—something upon which it might have a purchase, as a mechanic would say of a lever. The bend of the thread, then, on this view of the matter, would be carried out by the wind,—would form the point of impulsion,—and, of course, the escape bridge would be an ordinary line doubled.
Such was our conclusion, which was strongly corroborated by what we subsequently found said by M. Latreille—than whom no higher authority could be given. “When the animal,” says he, “desires to cross a brook, she fixes to a tree or some other object one of the ends of her first threads, in order that the wind or a current of air may carry the other end beyond the obstacle;”FH and as one end is always attached to the spinnerets, he must mean that the double of the thread flies off. In his previous publications, however, Latreille had contented himself with copying the statement of Dr. Lister.
In order to ascertain the fact, and put an end to all doubts, we watched, with great care and minuteness, the proceedings of the long-bodied spider above mentioned, by producing a stream of air in the same manner, as it perambulated the brim of the glass. It immediately, as the other had done, attached a thread, and raised its body perpendicularly, like a tumbler, standing on his hands with his head downwards; but we looked in vain for this thread bending, as we had at first supposed, and going off double. Instead of this it remained tight, while another thread, or what appeared to be so, streamed off from the spinners, similar to smoke issuing through a pin-hole, sometimes in a line, and sometimes at a considerable angle, with the first, according to the current of the air,—the first thread, extended from the glass to the spinnerets, remaining all the while tight drawn in a right line. It further appeared to us, that the first thread proceeded from the pair of spinnerets nearest the head, while the floating thread came from the outer pair,—though it is possible in such minute objects we may have been deceived. That the first was continuous with the second, without any perceptible joining, we ascertained in numerous instances, by catching the floating line and pulling it tight, in which case the spider glides along without attaching another line to the glass; but if she has to coil up the floating line to tighten it, as usually happens, she gathers it into a packet and glues the two ends tight together. Her body, while the floating line streamed out, remained quite motionless, but we distinctly saw the spinnerets not only projected, as is always done when a spider spins, but moved in the same way as an infant moves its lips when sucking. We cannot doubt, therefore, that this motion is intended to emit (if eject or project be deemed too strong words) the liquid material of the thread; at the same time, we are quite certain that it cannot throw out a single inch of thread without the aid of a current of air. A long-bodied spider will thus throw out in succession as many threads as we please, by simply blowing towards it; but not one where there is no current, as under a bell-glass, where it may be kept till it die, without being able to construct a bridge over water of an inch long. We never observed more than one floating thread produced at the same time; though other observers mention several.
The probable commencement, we think, of the floating line, is by the emission of little globules of the glutinous material to the points of the spinnerules—perhaps it may be dropped from them, if not ejected, and the globules being carried off by the current of air, drawn out into a thread. But we give this as only a conjecture, for we could not bring a glass of sufficient power to bear upon the spinnerules at the commencement of the floating line.
In subsequent experiments we found that it was not indispensable for the spider to rest upon a solid body when producing a line, as she can do so while she is suspended in the air by another line. When the current of air also is strong, she will sometimes commit herself to it by swinging from the end of the line. We have even remarked this when there was scarcely a breath of air.
We tried another experiment. We pressed pretty firmly upon the base of the spinnerets, so as not to injure the spider, blowing obliquely over them; but no floating line appeared. We then touched them with a pencil and drew out several lines an inch or two in length, upon which we blew in order to extend them; but in this also we were unsuccessful, as they did not lengthen more than a quarter of an inch. We next traced out the reservoirs of a garden-spider (Epeira diadema), and immediately taking a drop of the matter from one of them on the point of a fine needle, we directed upon it a strong current of air, and succeeded in blowing out a thick yellow line, as we might have done with gum-water, of about an inch and a half long.
When we observed our long-bodied spider eager to throw a line by raising up its body, we brought within three inches of its spinnerets an excited stick of sealing-wax, of which it took no notice, nor did any thread extend to it, not even when brought almost to touch the spinnerets. We had the same want of success with an excited glass rod; and indeed we had not anticipated any other result, as we have never observed that these either attract or repel the floating threads, as Mr. Murray has seen them do; nor have we ever seen the end of a floating thread separated into its component threadlets and diverging like a brush, as he and Mr. Bowman describe. It may be proper to mention that Mr. Murray, in conformity with his theory, explains the shooting of lines in a current of air by the electric state produced by motion in consequence of the mutual friction of the gaseous particles. But this view of the matter does not seem to affect our statements.
Nests, Webs, and Nets of Spiders.
The neatest, though the smallest spider’s nest which we have seen, was constructed in the chink of a garden post, which we had cut out in the previous summer in getting at the cells of a carpenter-bee. The architect was one of the large hunting-spiders, erroneously said by some naturalists to be incapable of spinning. The nest in question was about two inches high, composed of a very close satin-like texture. There were two parallel chambers placed perpendicularly, in which position also the inhabitant reposed there during the day, going, as we presume, only abroad to prey during the night. But the most remarkable circumstance was, that the openings (two above and two below) were so elastic, that they shut almost as closely as the boat cocoon of the Tortrix Chlorana. We observed this spider for several months, but at last it disappeared, and we took the nest out, under the notion that it might contain eggs; but we found none, and therefore conclude that it was only used as a day retreat. (J. R.) The account which Evelyn has given of these hunting-spiders is so interesting, that we must transcribe it.
“Of all sorts of insects,” says he, “there is none has afforded me more divertisement than the venatores (hunters), which are a sort of lupi (wolves) that have their dens in rugged walls and crevices of our houses; a small brown and delicately-spotted kind of spiders, whose hinder legs are longer than the rest. Such I did frequently observe at Rome, which, espying a fly at three or four yards’ distance, upon the balcony where I stood, would not make directly to her, but crawl under the rail till, being arrived at the antipodes, it would steal up, seldom missing its aim; but if it chanced to want anything of being perfectly opposite, would, at first peep, immediately slide down again,—till, taking better notice, it would come the next time exactly upon the fly’s back: but if this happened not to be within a competent leap, then would this insect move so softly, as the very shadow of the gnomon seemed not to be more imperceptible, unless the fly moved; and then would the spider move also in the same proportion, keeping that just time with her motion, as if the same soul had animated both these little bodies; and whether it were forwards, backwards, or to either side, without at all turning her body like a well-managed horse: but if the capricious fly took wing and pitched upon another place behind our huntress, then would the spider whirl its body so nimbly about, as nothing could be imagined more swift: by which means she always kept the head towards her prey, though, to appearance, as immovable as if it had been a nail driven into the wood, till by that indiscernible progress (being arrived within the sphere of her reach) she made a fatal leap, swift as lightning, upon the fly, catching him in the pole, where she never quitted hold till her belly was full, and then carried the remainder home.”
One feels a little sceptical, however, when he adds, “I have beheld them instructing their young ones how to hunt, which they would sometimes discipline for not well observing; but when any of the old ones did (as sometimes) miss a leap, they would run out of the field and hide themselves in their crannies, as ashamed, and haply not to be seen abroad for four or five hours after; for so long have I watched the nature of this strange insect, the contemplation of whose so wonderful sagacity and address has amazed me; nor do I find in any chase whatsoever more cunning and stratagem observed. I have found some of these spiders in my garden, when the weather, towards spring, is very hot, but they are nothing so eager in hunting as in Italy.”FI
We have only to add to this lively narrative, that the hunting-spider, when he leaps, takes good care to provide against accidental falls by always swinging himself from a good strong cable of silk, as Swammerdam correctly states,FJ and which anybody may verify, as one of the small hunters (Salticus scenicus), known by having its back striped with black and white like a zebra, is very common in Britain.
Mr. Weston, the editor of ‘Bloomfield’s Remains,’ falls into a very singular mistake about hunting-spiders, imagining them to be web-weaving ones which have exhausted their materials, and which are therefore compelled to hunt. In proof of this he gives an instance which fell under his own observation!FK
As a contrast to the little elastic satin nest of the hunter, we may mention the largest with which we are acquainted,—that of the labyrinthic spider (Agelena labyrinthica, Walchenaer). Our readers must often have seen this nest spread out like a broad sheet in hedges, furze, and other low bushes, and sometimes on the ground. The middle of this sheet, which is of a close texture, is swung like a sailor’s hammock, by silken ropes extended all around to the higher branches; but the whole curves upwards and backwards, sloping down to a long funnel-shaped gallery which is nearly horizontal at the entrance, but soon winds obliquely till it becomes quite perpendicular. This curved gallery is about a quarter of an inch in diameter, is much more closely woven than the sheet part of the web, and sometimes descends into a hole in the ground, though oftener into a group of crowded twigs, or a tuft of grass. Here the spider dwells secure, frequently resting with her legs extended from the entrance of the gallery, ready to spring out upon whatever insect may fall into her sheet net. She herself can only be caught by getting behind her and forcing her out into the web; but though we have often endeavoured to make her construct a nest under our eye, we have been as unsuccessful as in similar experiments with the common house spider (Aranea domestica). (J. R.)
The house spider’s proceedings were long ago described by Homberg, and the account has been copied, as usual, by almost every subsequent writer. Goldsmith has, indeed, given some strange misstatements from his own observations, and Bingley has added the original remark, that, after fixing its first thread, creeping along the wall, and joining it as it proceeds, it “darts itself to the opposite side, where the other end is to be fastened!”FL Homberg’s spider took the more circuitous route of travelling to the opposite wall, carrying in one of the claws the end of the thread previously fixed, lest it should stick in the wrong place. This we believe to be the correct statement, for as the web is always horizontal, it would seldom answer to commit a floating thread to the wind, as is done by other species. Homberg’s spider, after stretching as many lines by way of warp as it deemed sufficient between the two walls of the corner which it had chosen, proceeded to cross this in the way our weavers do in adding the woof, with this difference, that the spider’s threads were only laid on, and not interlaced.FM The domestic spiders, however, in these modern days, must have forgot this mode of weaving, for none of their webs will be found to be thus regularly constructed!
The geometric, or net-working spiders (Tendeuses, Latr.), are as well known in most districts as any of the preceding; almost every bush and tree in the gardens and hedge-rows having one or more of their nets stretched out in a vertical position between adjacent branches. The common garden spider (Epeira diadema), and the long-bodied spider (Tetragnatha extensa), are the best known of this order.
The chief care of a spider of this sort is, to form a cable of sufficient strength to bear the net she means to hang upon it; and, after throwing out a floating line as above described, when it catches properly she doubles and redoubles it with additional threads. On trying its strength she is not contented with the test of pulling it with her legs, but drops herself down several feet from various points of it, as we have often seen, swinging and bobbing with the whole weight of her body. She proceeds in a similar manner with the rest of the framework of her wheel-shaped net; and it may be remarked that some of the ends of these lines are not simple, but in form of a Y, giving her the additional security of two attachments instead of one.
In constructing the body of the net, the most remarkable circumstance is her using her limbs as a measure, to regulate the distances of her radii or wheel-spokes, and the circular meshes interweaved into them. These are consequently always proportional to the size of the spider. She often takes up her station in the centre, but not always, though it is so said by inaccurate writers; for she as frequently lurks in a little chamber constructed under a leaf or other shelter at the corner of her web, ready to dart down upon whatever prey may be entangled in her net. The centre of the net is said also to be composed of more viscid materials than its suspensory lines,—a circumstance alleged to be proved by the former appearing under the microscope studded with globules of gum.FN We have not been able to verify this distinction, having seen the suspensory lines as often studded in this manner as those in the centre. (J. R.)
A no less wonderful structure is composed by a sort of spiders, natives of the tropics and the south of Europe, which have been justly called mason-spiders by M. Latreille. One of these (Mygale nidulans, Walckn.), found in the West Indies, “digs a hole in the earth obliquely downwards about three inches in length, and one in diameter. This cavity she lines with a tough thick web, which, when taken out, resembles a leathern purse; but, what is most curious, this house has a door with hinges, like the operculum of some sea-shells, and herself and family, who tenant this nest, open and shut the door whenever they pass and repass. This history was told me,” says Darwin, “and the nest, with its door, shown me by the late Dr. Butt, of Bath, who was some years physician in Jamaica.”FO
The nest of a mason-spider, similar to this, has been obligingly put into our hands by Mr. Riddle, of Blackheath. It came from the West Indies, and is probably that of Latreille’s clay-kneader (Mygale cratiens), and one of the smallest of the genus. We have since seen a pair of these spiders in possession of Mr. William Mello, of Blackheath. The nest is composed of very hard argillaceous clay, deeply tinged with brown oxide of iron. It is in form of a tube, about one inch in diameter, between six and seven inches long, and slightly bent towards the lower extremity—appearing to have been mined into the clay rather than built. The interior of the tube is lined with a uniform tapestry of silken web, of an orange-white colour, with a texture intermediate between India paper and very fine glove leather. But the most wonderful part of this nest is its entrance, which we look upon as the perfection of insect architecture. A circular door, about the size of a crown piece, slightly concave on the outside and convex within, is formed of more than a dozen layers of the same web which lines the interior, closely laid upon one another, and shaped so that the inner layers are the broadest, the outer being gradually less in diameter, except towards the hinge, which is about an inch long; and in consequence of all the layers being united there, and prolonged into the tube, it becomes the thickest and strongest part of the structure. The elasticity of the materials, also, gives to this hinge the remarkable peculiarity of acting like a spring, and shutting the door of the nest spontaneously. It is, besides, made to fit so accurately to the aperture, which is composed of similar concentric layers of web, that it is almost impossible to distinguish the joining by the most careful inspection. To gratify curiosity, the door has been opened and shut hundreds of times, without in the least destroying the power of the spring. When the door is shut, it resembles some of the lichens (Lecidea), or the leathery fungi, such as Polyporus versicolor (Micheli), or, nearer still, the upper valve of a young oyster shell. The door of the nest, the only part seen above ground, being of a blackish-brown colour, it must be very difficult to discover. (J. R.)
Another mason-spider (Mygale cæmentaria, Latr.), found in the south of France, usually selects for her nest a place bare of grass, sloping in such a manner as to carry off the water, and of a firm soil, without rocks or small stones. She digs a gallery a foot or two in depth, and of a diameter (equal throughout) sufficient to admit of her easily passing. She lines this with a tapestry of silk glued to the walls. The door, which is circular, is constructed of many layers of earth kneaded, and bound together with silk. Externally, it is flat and rough, corresponding to the earth around the entrance, for the purpose, no doubt, of concealment: on the inside it is convex, and tapestried thickly with a web of fine silk. The threads of this door-tapestry are prolonged, and strongly attached to the upper side of the entrance, forming an excellent hinge, which, when pushed open by the spider, shuts again by its own weight, without the aid of spring hinges. When the spider is at home, and her door forcibly opened by an intruder, she pulls it strongly inwards, and even when half-opened often snatches it out of the hand; but when she is foiled in this, she retreats to the bottom of her den, as her last resource.FP
Rossi ascertained that the female of an allied species (Mygale sauvagesii, Latr.), found in Corsica, lived in one of these nests, with a numerous posterity. He destroyed one of these doors to observe whether a new one would be made, which it was; but it was fixed immovably, without a hinge; the spider, no doubt, fortifying herself in this manner till she thought she might reopen it without danger.FQ
The nest is nearly six inches in length, and is made of a double layer of silken web. The inner layer is yellowish, with a tinge of red, and although fine, very tough and strong. The outer layer is thick, coarse, dark brown, and rather flaky, the dark colour being probably caused by the earth which is mixed with it. The lid is made of eight or ten layers of coarse web, overlapping each other like the tiles of a house-roof, and the entrance of the nest is formed after the same fashion. If the lid be opened, the inside of the nest is seen to be of a different make from the exterior, being greyish-white, smooth, close-textured, and looking much like the finest kid leather.
[The smaller illustration shows the spider in the act of emerging from its home.]
“The Rev. Revett Shepherd has often noticed, in the fen ditches of Norfolk, a very large spider (the species not yet determined) which actually forms a raft for the purpose of obtaining its prey with more facility. Keeping its station upon a ball of weeds about three inches in diameter, probably held together by slight silken cords, it is wafted along the surface of the water upon this floating island, which it quits the moment it sees a drowning insect. The booty thus seized it devours at leisure upon its raft, under which it retires when alarmed by any danger.”FR In the spring of 1830, we found a spider on some reeds in the Croydon Canal, which agreed in appearance with Mr. Shepherd’s.
Among our native spiders there are several besides this one, which, not contented with a web like the rest of their congeners, take advantage of other materials to construct cells where, “hushed in grim repose,” they “expect their insect prey.” The most simple of those spider-cells is constructed by a longish-bodied spider (Aranea holosericea, Linn.), which is a little larger than the common hunting-spider. It rolls up a leaf of the lilac or poplar, precisely in the same manner as is done by the leaf-rolling caterpillars, upon whose cells it sometimes seizes to save itself trouble, having first expelled, or perhaps devoured, the rightful owner. The spider, however, is not satisfied with the tapestry of the caterpillar, but always weaves a fresh set of her own, much more close and substantial.
Another spider, common in woods and copses (Epeira quadrata?), weaves together a great number of leaves to form a dwelling for herself, and in front of it she spreads her toils for entrapping the unwary insects which stray thither. These, as soon as caught, are dragged into her den, and stored up for a time of scarcity. Here also her eggs are deposited and hatched in safety. When the cold weather approaches, and the leaves of her edifice wither, she abandons it for the more secure shelter of a hollow tree, where she soon dies; but the continuation of the species depends upon eggs, deposited in the nest before winter, and remaining to be hatched with the warmth of the ensuing summer.
The spider’s den of united leaves, however, which has just been described, is not always useless when withered and deserted, for the dormouse usually selects it as a ready-made roof for its nest of dried grass. That those old spiders’ dens are not accidentally chosen by the mouse, appears from the fact, that out of about a dozen mouse-nests of this sort found during winter in a copse between Lewisham and Bromley, Kent, every second or third one was furnished with such a roof. (J. R.)
Diving Water-Spider.
Though spiders require atmospheric air for respiration, yet one species well known to naturalists is aquatic in its habits, and lives not only upon the surface but below the surface of the water, contriving to carry down with it a sufficiency of air for the support of life during a considerable period of time. Its subaqueous nest is in fact a sort of diving-bell, and constitutes a secure and most ingenious habitation. This spider does not like stagnant water, but prefers low running streams, canals, and ditches, where she may often be seen in the vicinity of London and elsewhere, living in her diving-bell, which shines through the water like a little globe of silver: her singular economy was first, we believe, described by Clerck,FS L. M. de Lignac,FT and De Geer.
“The shining appearance,” says Clerck, “proceeds either from an inflated globule surrounding the abdomen, or from the space between the body and the water. The spider, when wishing to inhale the air, rises to the surface, with its body still submersed, and only the part containing the spinneret rising just to the surface, when it briskly opens and moves its four teats. A thick coat of hair keeps the water from approaching or wetting the abdomen. It comes up for air about four times an hour or oftener, though I have good reason to suppose it can continue without it for several days together.
“I found in the middle of May one male and ten females, which I put into a glass filled with water, where they lived together very quietly for eight days. I put some duckweed (Lemna) into the glass to afford them shelter, and the females began to stretch diagonal threads in a confused manner from it to the sides of the glass about half-way down. Each of the females afterwards fixed a close bag to the edge of the glass, from which the water was expelled by the air from the spinneret, and thus a cell was formed capable of containing the whole animal. Here they remained quietly, with their abdomens in their cells, and their bodies still plunged in the water; and in a short time brimstone-coloured bags of eggs appeared in each cell, filling it about a fourth part. On the 7th of July several young ones swam out from one of the bags. All this time the old ones had nothing to eat, and yet they never attacked one another as other spiders would have been apt to do.”FU
“These spiders,” says De Geer, “spin in the water a cell of strong, closely-woven white silk, in the form of half the shell of a pigeon’s egg, or like a diving-bell. This is sometimes left partly above water, but at others is entirely submersed, and is always attached to the objects near it by a great number of irregular threads. It is closed all round, but has a large opening below, which, however, I found closed on the 15th of December, and the spider living quietly within, with her head downwards. I made a rent in this cell, and expelled the air, upon which the spider came out; yet, though she appeared to have been laid up for three months in her winter quarters, she greedily seized upon an insect and sucked it. I also found that the male as well as the female constructs a similar subaqueous cell, and during summer no less than in winter.”FV We have recently kept one of these spiders for several months in a glass of water, where it built a cell half under water, in which it laid its eggs.
Cleanliness of Spiders.
When we look at the viscid material with which spiders construct their lines and webs, and at the rough, hairy covering (with a few exceptions) of their bodies, we might conclude that they would be always stuck over with fragments of the minute fibres which they produce. This, indeed, must often happen, did they not take careful precautions to avoid it; for we have observed that they seldom, if ever, leave a thread to float at random, except when they wish to form a bridge. When a spider drops along a line, for instance, in order to ascertain the strength of her web, or the nature of the place below her, she invariably, when she reascends, coils it up into a little ball, and throws it away. Her claws are admirably adapted for this purpose, as well as for walking along the lines, as may be readily seen by a magnifying glass.
There are three claws, one of which acts as a thumb, the others being toothed like a comb, for gliding along the lines. This structure, however, unfits it to walk, as flies can do, upon any upright polished surface like glass; although the contraryFW is erroneously asserted by the Abbé de la Pluche. Before she can do so, she is obliged to construct a ladder of ropes, as Mr. Blackwell remarks,FX by elevating her spinneret as high as she can, and laying down a step upon which she stands to form a second, and so on; as any one may try by placing a spider at the bottom of a very clean wine-glass.
The hairs of the legs, however, are always catching bits of web and particles of dust; but these are not suffered to remain long. Most people may have remarked that the house-fly is ever and anon brushing its feet upon one another to rub off the dust, though we have not seen it remarked in authors that spiders are equally assiduous in keeping themselves clean. They have, besides, a very efficient instrument in their mandibles or jaws, which, like their claws, are furnished with teeth; and a spider which appears to a careless observer as resting idly, in nine cases out of ten will be found slowly combing her legs with her mandibles, beginning as high as possible on the thigh, and passing down to the claws. The flue which she thus combs off is regularly tossed away.
With respect to the house-spider (A. domestica), we are told in books, that “she from time to time clears away the dust from her web, and sweeps the whole by giving it a shake with her paw, so nicely proportioning the force of her blow, that she never breaks anything.”FY That spiders may be seen shaking their webs in this manner, we readily admit; though it is not, we imagine, to clear them of dust, but to ascertain whether they are sufficiently sound and strong.
We recently witnessed a more laborious process of cleaning a web than merely shaking it. On coming down the Maine by the steamboat from Frankfort, in August, 1829, we observed the geometric-net of a conic-spider (Epeira conica, Walck.) on the framework of the deck, and as it was covered with flakes of soot from the smoke of the engine, we were surprised to see a spider at work on it; for, in order to be useful, this sort of net must be clean. Upon observing it a little closely, however, we perceived that she was not constructing a net, but dressing up an old one; though not, we must think, to save trouble, so much as an expenditure of material. Some of the lines she dexterously stripped of the flakes of soot adhering to them; but in the greater number, finding that she could not get them sufficiently clean, she broke them quite off, bundled them up, and tossed them over. We counted five of these packets of rubbish which she thus threw away, though there must have been many more, as it was some time before we discovered the manœuvre, the packets being so small as not to be readily perceived, except when placed between the eye and the light. When she had cleared off all the sooty lines, she began to replace them in the usual way; but the arrival of the boat at Mentz put an end to our observations. (J. R.) Bloomfield, the poet, having observed the disappearance of these bits of ravelled web, imagined that the spider swallowed them; and even says that he observed a garden spider moisten the pellets before swallowing them!FZ Dr. Lister, as we have already seen, thought the spider retracted the threads within the abdomen.