The Parents' Review
A Monthly Magazine of Home-Training and Culture
"Education is an atmosphere, a discipline, a life."
The Habits of Insects.
by Rev. A. Thornley, M.A., F.E.S.
Spiders. [spider image]
Cobwebs! How frequently are they associated with dirt and desolation. Who would believe that a spider's web has its beautiful side! Yet the most unobservant person cannot fail to be struck with the great beauty of the geometric web of our common garden spider: and to be filled with delight when, as the misty autumn morning clears, he beholds fields and hedgerows covered with a delicate network of spiders' webs, like finest gauze. A little patient study of the work of spiders will bring out many wonders, and therefore I will ask you to accompany me into the garden, while we seek for one of those beautiful circular webs, common everywhere. Here is one. It is in the corner of an empty window frame of an old toolhouse. In choosing such a spot, it is obvious the spider has got rid of many difficulties. For instance, there are capital points of attachment for its lines, close at hand; and where these are wanting, a single strong thread spun, as we see, across the angle, supplies all that is necessary. It is wonderful to observe the many devices by which a spider overcomes its web-making difficulties. In order to get a line across a certain space, it must sometimes walk a very long way round, and occasionally drop to the ground, and ascend to the wished for point by some neighbouring object; but if some light air or draught be available it has recourse to an ingenious device for accomplishing this purpose. Elevating its abdomen in the direction of the wind, it emits from its spinnerets a silken thread of some length, which, catching in the wind, is carried against some point of support, to which it adheres by virtue of a certain viscosity. A natural bridge being thus formed, the spider readily crosses by it, and fixes her line. In this manner the outer boundary lines are laid, and it is then a comparatively easy task to stretch from the centre, the beautiful radiating lines. The little creature commences by stretching across the space thus marked out, what we might call a diagonal line: from the centre of this she stretches her first true radial line, following it by others, until the growing web presents that wheel-like appearance so well known. And now the real weaving commences. But before beginning this work, it is asserted by good observers that the spider frequently returns to the centre, and tries with her feet each line, substituting a new one for any that may be defective; then, beginning at the centre, she spins five or six fine concentric circles of silk close together, and after this, a few larger ones further apart. She then sets off along one of the radii, and fixing a thread near to its extremity, walks back towards the centre, her line running out after her, and steps over to the adjoining radius; there she draws her line taut and fixes it. In this manner she proceeds until the connecting circle is complete, as well as all the rest which follow it in regular and beautiful order. Thus in the space of sometimes little over an hour the wonderful geometrical web is made. Sometimes, however, a thing happens, which I have not yet observed myself, and therefore relate on the testimony of others. The web being apparently finished, the little architect returns once more to the centre, and bites away the cotton(?) like tuft formed by the union of all the radial lines, and which is now no longer necessary to hold these together. The result of this action is to produce that little circular aperture nearly always observed in the centre of the web. This is all I can tell you at present about the making of a spider's web. There are yet a great many points to be cleared up; and I think it would be a good thing, if one of our scientific societies would offer a prize for the best description, from original observation, of the mode in which a spider constructs its wonderful net. But whether this will ever be so or not, I hope I have sufficiently roused the enthusiasm of my readers to induce them to make some observations of their own on this very interesting subject. I daresay some have already noticed that I have very freely used the pronoun "she" in the above description, and this indeed I have been obliged to do, for the "lady spider" is in every way "the better half." Very warily has "my lord" to pay his devoirs, for any unnecessary bashfulness on his part but precipitates his fate, which is, alas, to be eaten up.
If I have said enough about the way, we may now look at the means by which the spiders accomplish such wonderful results. With what instruments, and what materials do they work? Now the material out of which a web is made is a kind of silk, which is secreted as a viscid fluid by certain glands in the spider's body, and so viscid that it can be drawn out into long threads, which, by exposure to the air, rapidly harden. It is emitted through the fine tubes of an organ called a "spinneret," situated at the extremity of the abdomen. An ordinary spider usually possesses four of these, but in some species an extra pair are to be seen. Under a lens they present the appearance of four little nipples projecting from the extremity of the abdomen. Now it is a very interesting point that whilst the boundary and radial lines of a spider's web are made of perfectly plain and almost inelastic silk, the greater number of the inter-radial lines are made of quite a different quality of that substance, for it is of a finer make and very elastic, and when examined under a lens is seen to be studded at close intervals with little shiny globules of a viscid fluid; yet the innermost circles of all are made of ordinary silk, the viscid globules being absent. It is of course easy to see the reason of this difference. The centre of the web is the spider's resting place. Here she hangs, head downwards, her legs extended along the threads, so that the slightest vibration of the web is perceived by her at once. It is a nice instinct which prompts her thus to spread her bird-line at a proper distance away. It will scarcely be necessary to remind you that a net of this description is always placed in a more or less vertical position, for being more or less at right angles to the direction of the flight of insects, it will be more likely to snare them than if placed horizontally. It is a well ascertained fact that the lines with the viscid globules are renewed daily, if not oftener. To keep the threads clear of one another during the delicate operation of web-making the hind feet of some spiders are provided with a singular instrument, not unlike a little comb, by means of which the little creature guides each thread, keeping it clear of obstacles and preventing it from becoming entangled with loose threads. It is a pretty sight to watch a spider making her web, to note the terrible earnestness and unwarying industry she displays, the little pauses when she seems to be settling some knotty question, and the rapidity with which she works when a practical solution dawns upon her. She may well have stimulated the flagging energy of a Bruce, and like the bees may point the moral of the old latin poet, "Improbus labor, omnia vincit."
Whilst upon this subject of silk producing, I will say a few words about a phenomenon occasionally observed on fine calm days in autumn. Taking our morning walk we behold the ground and herbage covered with a vast multitude of fine webs, and the air filled with floating silken threads. This appearance is usually known by the name of "gossamer," a word which has given great trouble to philologists, but which if we are to accept Professor Skeat's explanation, admits of a very simple derivation, namely, "goose summer." Nor is this explanation unreasonable when we call to mind the appearance presented in the neighbourhood of a pond where the geese have been cleaning their feathers. We are not surprised that this extraordinary sight received many curious and absurd explanations from our unscientific forefathers. The poet Spenser imagined that it was the result of "scorched dew," and others, by a wilder stretch of imagination, regarded it as the same substance out of which light summer clouds were made. The power of observation in our forefathers seems on the average to have been very small; little encouragement was given to scientific training in those days, so that Nature's problems when she produced any, were usually answered by drawing upon a lively imagination or making a happy guess. The well-known axiom of scientific advance, namely, to reason from what we know to what we do not know, seems to have been pretty generally reversed, and hence the most extraordinary blunders were propagated as sober truth. A little investigation soon discovers that spiders are at the bottom of the Gossamer. If one of the floating threads be caught and examined, it is very probable that a tiny spider will be perceived at the end of it, and indeed these aeronautic gambols are one way in which some species of young spiders enjoy themselves. Though a good deal is known about the Gossamer yet much of the secret remains for you to unravel. Spiders have, however, frequently been detected in the very act of "going up." A juvenile specimen was seen to ascend a post in order to attain a sufficient elevation for his launch off, then erecting his abdomen into an almost vertical position, he shot out rapidly from it a fine thread, then estimating by a nice instinct the quantity necessary for flotation, he cast himself loose in a gentle current of air, and was at once gracefully borne aloft. So high indeed do the spiders ascend in their aerial voyage, that they have been perceived in numbers in the air by an observer on the top of the highest tower of York Minster. Many kinds of spider do not spin webs, but catch their prey by giving chase to it. Fleet of limb, and strong of body, they are the wolves of the tribe, and to such perfection is this mode of capture carried, that one species, found not uncommonly on the banks of ponds and ditches, actually pursues its prey into the water. Another well-known spider, the beautiful Dolomedes Fimbriatus, of the Fen country, unites together with silken threads fragments of rushes or dead leaves, so forming a little raft; and from this coign of vantage it pounces upon any luckless insect that has fallen into the water, or any aquatic creature coming to the surface to breathe. It is said to run upon the water in pursuit of its prey with as much agility as it does upon land. The passage from these semi-aquatic forms to one entirely adapted to a watery environment is seen in the well-known Argyroneta Aquatica or Water Spider, par excellence. This species, at one time quite common, but now, owing to the pollution of so many streams, becoming rarer every year, is perhaps one of the most interesting creatures in all the range of animal life. It can be easily kept in an aquarium, so permitting of the leisurely study of its habits. It constructs an oval nest of pure white water-tight silk, and attaches it to the leaves or stems of some water plant. This is her home and fortress. Here she brings up her family, or devours at leisure her luckless prey. But the interest of this nest centres about the method by which she fills it, and keeps it filled, with air. It was a long time before the true solution of this problem was found, and there are yet some points remaining to be investigated. Having completed her nest, the little creature ascends to the surface, and elevating the extremity of her abdomen momentarily above the water, draws underneath a bubble of air which is entangled, as it were, amongst the interstices of the long rough hairs with which her body is clothed. To assist in retaining her precious burden, and to prevent it being too readily dislodged by an unlucky contact with some obstacle, the sensible little creature extends and crosses her hind legs, and with the help of these holds in its place the bubble of air. She then carefully descends and discharges the bubble at the orifice of the nest; and this being situated at the lowest point of the structure, the air bubble naturally ascends into it, driving out a small portion of the water. This expedient is repeated until the little structure is filled with air; and now, owing to the diving bell principle upon which it has been contructed, it is an easy matter to keep the water out, a fresh bubble of air being added as the fromer supply becomes a little exhausted. The Water Spider is a large dull reddish species, with an olive brown body, thickly covered with rough hairs, which subserve indirectly the purpose of respiration. It is thus enabled to carry a constant supply about with it, and very pretty it looks when seen swimming about the recesses of its pool, clothed with its silvery mantle of air.
And now I want to tell you about some spiders which make nests of quite a different character to these which we have just been considering. From a certain peculiarity of their dwellings they are called "Trap-door" Spiders. Most of the species excavate in a sloping clay bank, a tubular burrow about a foot long, and nearly an inch wide, though these proportions vary much with the different species. The inside of the burrow is then lined with silk, and the aperture closed with an ingenious little circular door, made of alternate layers of silk and earth, and as true in its proportions as if the little architect had employed a pair of compasses in its fabrication. Not unfrequently this little door is covered with moss, which disguises it so completely that even a practised eye fails to distinguish it from the surface of the ground. The precision with which the little lid fits its aperture is secured through the device of bevelling it away at the edges; the hinge too, by which it is secured, is always, by a wonderful instinct, placed at the highest point of the circular opening; thus, it naturally shuts to at the ingress or egress of its owner. It is no easy task to raise one of the little lids if the occupier be at home. The brave little creature seizing the lining of its tube with its fore feet, fixes its hind feet in the silken pad of its little door, and holds on almost to the point of being pulled in pieces. If we think for a moment of the amount of toil and industry displayed by this little spider, the variety of instincts it exhibits, and the beautiful workmanship that results from its efforts, we cannot fail to be filled with a sublime sense of wonder mixed with awe, at the Infinite Mind which called all this energy into existence. The species of Trap-door Spiders are widely distributed, being represented in most parts of the world, but the finest specimens come to us from the West Indies. I have, however, received very beautiful examples of a smaller species from Italy; indeed a somewhat aberrant member of the group has been found in the South of England. This species (Atypus Piceus), though it constructs a long silken tube, does not close the entrance to its dwelling with a door, but prolongs the silken lining several inches beyond its exit from the ground, so that the aerial portion forms a kind of flap which naturally closes its burrow.
Now all the spiders we have been considering are of small size; but it was reported many years ago, that gigantic spiders, several inches long and larger than many a bird, were to be seen in South America. Such reports were at first received by naturalists with great incredulity, but the observations of the late Mr. H. W. Bates, F.R.S., during a lengthy sojourn in the region of the river Amazon, have shown us that the earlier reports contained more truth than was suspected at the time. For this accurate and careful observer relates how on one occasion he discovered a large spider in a deep crevice of a tree. This monster was nearly two inches in length of body, and with its long legs expanded must have covered half a square foot of ground. Across the deep fissure in which it was hiding, was stretched a dense white web, the lower part of which was apparently broken by the struggles of two small birds, which lay entangled in its fragments. One was dead, the other which died soon after its removal was smeared with a slimy saliva, which Mr. Bates not unreasonably imagined had been ejected by the spider. Whether the horrid creature had actually entrapped and killed the birds, or whether they had been caught in the web by accident, must be a matter of conjecture. I believe that some of these monsters have been kept in the Insect House, at the Zoo, and that on one occasion one was seen to attack and kill a mouse.
Tradition, moreover, has associated very terrible results with the bites of some kind of spiders. We have all of us read of the dreadful and venomous "Tarantula" (Lycus Tarantula), a "Wolf" spider common in the South of Europe, the bite of which was asserted to prodcuce a singular kind of madness. The person bitten was seized with a dancing mania, to cure which the homeopathic principle of "like cures like" was applied. The poor sufferer was forced to dance to the lively strains of certain musical compositions, fitly called "Tarantelles," and encouraged to keep up this vigorous exercise until exhaustion set in, when, naturally enough, death or cure resulted. Modern investigation however, has shown that in this, as in many similar cases, there was more of fraud than truth. For it appears that the bite of the Tarantula in ordinary circumstances, results in little more than a slight swelling and inflammation.
But I see that the space at my disposal is rapidly drawing to a close, and indeed is almost finished; and though I had purposed at the beginning of this article, to say something about the structure of spiders, I must for the present relinguish this idea. I hope what I have said may result in some valuable contributions by some of you, to our yet very defective knowledge of the habits and instincts of Insects.
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