Emotions.

The emotional life of spiders, so far as we can observe it as expressed in their actions, seems to be divided between sexual passion (including maternal affection) and the sterner feelings incidental to their fiercely predatory habits. But the emotions, although apparently few and simple in character, are exceedingly strong in force. In many species the male spider in conducting his courtship has to incur an amount of personal danger at the hands (and jaws) of his terrific spouse, which might well daunt the courage of a Leander. Ridiculously small and weak in build, the males of these species can only conduct the rites of marriage with their enormous and voracious brides by a process of active manoeuvring, which if unsuccessful is certain to cost them their lives. Yet their sexual emotions are so strong that, as proved by the continuance of the species, no amount of personal risk is sufficient to deter them from giving these emotions full play. There is no other case in the animal kingdom where courtship is attended with any approach to the gravity of danger that is here observable. Among many animals the males have to meet a certain amount of inconvenience from the coquetry or disinclination of the females; but here the coquetry and disinclination has passed into the hungry determination of a ferocious giantess. The case, therefore, because unique, is of interest from an evolutionary point of view. We can see a direct advantage to species from the danger incurred by males on account of mutual jealousy; for this, giving rise to what Mr. Darwin has called 'the law of battle,' must obviously be a constant source of the creation and the maintenance of specific proficiency; the law of battle determines that only the strongest and most courageous males shall breed. But the benefit to species is not so obvious where the danger of courtship arises from the side of the female. Still, that there must be some benefit is obvious, seeing that the whole structure of the male, if we take that of the female as the original type, has been greatly modified with reference to this danger: had the latter been wholly useless, either it would not have been allowed to arise, or the species must have become extinct. The only suggestion I can make to meet this aberrant case is that the courage and determination required of the male, besides being no doubt of use to him in other relations in life, may be of benefit to the species by instilling these qualities into the psychology both of his male and female descendants.

The courage and rapacity of spiders as a class are too well and generally known to require special illustration. One instance, however, may be quoted to show the strength of their maternal emotions. Bonnet threw a spider with her bag of eggs into the pit of an ant-lion. The latter seized the eggs and tore them away from the spider; but although Bonnet forced her out of the pit, she returned, and chose to be dragged in and buried alive rather than leave her charge.

The only other point that occurs to me with reference to the emotions of spiders is the somewhat remarkable one concerning their apparent fondness of music. The testimony is so varied and abundant on this matter that we can scarcely doubt the truth of the facts. These simply are that spiders—or at any rate some species or individuals—approach a sounding musical instrument, 'especially when the music is tender and not too loud.' They usually approach as near as possible, often letting themselves down from the ceiling of the room by a line of web, and remain suspended above the instrument. Should the music become loud, they often again retreat. Professor C. Reclain, during a concert at Leipsic, saw a spider descend in this way from one of the chandeliers while a violin solo was being played; but as soon as the orchestra began to sound it quickly ran back again.[75] Similar observations have been published by Rabigot, Simonius, von Hartmann, and others.

A highly probable explanation of these facts has recently been given by Mr. C. V. Boys, which relieves us of the necessity of imputing to animals so low in the scale any rudiment of Æsthetic emotion as aroused by musical tones. As the observation is an interesting one, I shall quote it in extenso:—

General Habits.

Coming now to general habits, our attention is claimed by the only general habit that is of interest—namely, that of web-building. The instinct of constructing nets for the capture of prey occurs in no other class of animals, while in spiders it not only attains to an extraordinary degree of perfection (so that, in the opinion of some geometers, the instinct is not less wonderful in this respect than is that displayed by the hive-bee in the construction of its cells), but also ramifies into a number of diverse directions. Thus we have, in different species, wide open networks spread between the branches of bushes, &c., closely woven textures in the corners of buildings, earth tubes lined with silk, the strong muslin-like snare of the Mygale, which, as first noticed by Madame Merian,[77] and since confirmed by Bates,[78] is able to retain a struggling humming-bird while this most beautiful animal in creation is being devoured by the most repulsive; and many other varieties might be mentioned. It may at first sight appear somewhat remarkable that this instinct of spreading snares should on the one hand occur only in one class of the animal kingdom, while on the other hand, in the class where it does occur, it should attain such extreme perfection, and run into so much variety. But we must here remember that the development of the instinct obviously depends upon the presence of a web-secreting apparatus, which is a comparatively rare anatomical feature. In caterpillars, which are not predaceous, the web is used only for the purposes of protection and locomotion; and it is easy to see that the spreading of snares would here be of no use to the animals. But in spiders, of course, the case is otherwise. Once granting the power of forming a web, and it is evident that there is much potential service to which this power may be put with reference to the voracious habits of the animal; and therefore it is not to be wondered that both the anatomical structures and their correlated instincts should attain to extreme perfection in sundry lines of development. The origin of the web-building structure was probably due to the use of the web for purposes of locomotion or of cocoon-spinning, as we see it still so used in the same way that it is used by caterpillars for descending from heights, and in the case of the gossamer spider for travelling immense distances through the air. As the anatomical structures in question differ very greatly in the case of spiders and in that of caterpillars, we may wonder why analogous if not homologous structures should never have been developed in the case of any other animal having predaceous habits—especially, perhaps, in that of the imago form of predaceous insects. It is easy to see how, if there were any original tendency to secrete a viscid substance in the neighbourhood of the anus, this might be utilised in descending from low elevations (as certain kinds of slugs use their viscid slime as threads whereby to let themselves down from low branches to the ground); and so we can understand how natural selection might thus have the material supplied out of which to develop such highly specialised organs as the spinnerets of a spider. But if we are inclined to wonder why this should not have happened among other animals, we must remember that any expectation that it should rests on negative grounds; we have no reason to suppose that in any other case the initial tendency to secrete a viscid substance was present. One inference, however, in the case of spiders seems perfectly valid. As this comparatively rare faculty of web-spinning occurs so generally throughout the class, it must have had its earliest origin very far back in the history of that class, though probably not so far back as to include the common progenitors of the spiders and the scorpions, seeing that the latter do not spin webs.

I shall now give a few details on the manner in which spiders' webs are made. Without going into the anatomy of the subject further than to observe that a spider's 'thread' is a composite structure made up of a number of finer threads, which leave their respective spinneret-holes in an almost fluid condition, and immediately harden by exposure to the air, I shall begin at once to describe the method of construction.

The so-called 'geometric spider' constructs her web by first laying down the radiating and unadhesive rays, and then, beginning from the centre, spins a spiral line of unadhesive web, like that of the rays which it intersects. This line, in being woven through the radii in a spiral from centre to circumference, serves as a scaffolding for the spider to walk over, and also keeps the rays properly stretched. She next spins another spiral line, but this time from the circumference to near the centre, and formed of web, covered with a viscid secretion to retain prey. Lastly, she constructs her lair to bide and watch for prey, at some distance from the web but connected with it by means of a line of communication or telegraph, the vibrations of which inform her of the struggling of an insect in the net.[79]

According to Thompson,—

According to BÜchner,—

Special Habits.

Water-spider.—The water-spider (Argyroneta aquatica), as is well known, displays the curious instinct of building her nest below the surface of water, and constructing it on the principle of a diving-bell. The animal usually selects still waters for this purpose, and makes her nest in the form of an oval hollow, lined with web, and held secure by a number of threads passing in various directions and fastened to the surrounding plants. In this oval bell, which is open below, she watches for prey, and, according to Kirby,[82] passes the winter after having closed the opening. The air needful for respiration the spider carries from the surface of the water. To do this she swims upon her back in order to entangle an air-bubble upon the hairy surface of her abdomen. With this bubble she descends, 'like a globe of quicksilver,' to the opening of her nest, where she liberates it and returns for more.

The Vagrant or Wolf Spider.—This insect catches its prey by stealthily stalking it until within distance near enough to admit of a sudden dart being successful in effecting capture. Some species, before making the final dart (e.g. Salticus scenicus), fix a line of web upon the surface over which they are creeping, so that whether their station is vertical or horizontal with reference to the prey, they can leap fearlessly, the thread in any case preventing their fall. Dr. H. F. Hutchinson says that he has seen this spider crawling over a looking-glass stalking its own reflection.[83]

The following is quoted from BÜchner:—

Trap-door Spiders.—These display the curious instinct of providing their nests with trap-doors. The nest consists of a tube excavated in the earth to the depth of half a foot or more. In all save one species the tube is unbranched; it is always lined with silk, which is continuous with the lining of the trap-door or doors, of which it forms the hinge. In the species which constructs a branching tube, the branch is always single, more or less straight, takes origin at a point situated a few inches from the orifice of the main tube, is directed upwards at an acute angle with that tube, and terminates blindly just below the surface of the soil. At its point of junction with or departure from the main tube it is provided with a trap-door resembling that which closes the orifice of the main tube, and of such a size and arrangement that when closed against the opening of the branch tube it just fills that opening; while when turned outwards, so as to uncork this opening, it just fills the diameter of the main tube: the latter, therefore, is in this species provided with two trap-doors, one at the surface of the soil, and the other at the fork of the branched tube.

Each species of trap-door spider is very constant in building a particular kind of trap-door; but among the different species there are four several kinds of trap-doors to be distinguished. 1st. The single-door cork nest, wherein the trap-door is a thick structure, and fits into the tube like a cork into a bottle. 2nd. The single-door wafer nest, wherein the trap-door is as thin as a piece of paper. 3rd. The double-door unbranched nest, wherein there is a second trap-door situated a few inches below the first one. And 4th, the double-door branched nest already described. In all cases the trap-doors open outwards, and when the nest is placed, as it usually is, on a sloping bank, the trap-door opens upwards; hence there is no fear of its gaping, for gravity is on the side of holding it shut.

The object of the trap-door is to conceal the nest, and for this purpose it is always made so closely to resemble the general surface of the ground on which it occurs, that even a practised eye finds it difficult to detect the structure when closed. In order to make the resemblance to the surrounding objects as perfect as possible, the spider either constructs the surface of its door of a portion of leaf, or weaves moss, grass, &c., into the texture. Moggridge says,[84]—

If an enemy should detect the trap-door and endeavour to open it, the spider frequently seizes hold of its internal surface, and, applying her legs to the walls of the tube, forcibly holds the trap-door shut. In the double trap-door species it is surmised that the second trap-door serves as an inner barrier of defence, behind which the spider retires when obliged to abandon the first one. In the branched tube species (which, so far as at present known, only occurs in the south of Europe) it is surmised that the spider, when it finds that an enemy is about to gain entrance at the first trap-door, runs into the branch tube and draws up behind it the second trap-door. The surface of this trap-door, being overlaid with silk like the walls of the tube, is then invisible; so that the enemy no doubt passes down the main tube to find it empty, without observing the lateral branch in which the spider is concealed behind the closed door.

As showing that these animals are to no small extent able to adapt their dwellings to unusual circumstances, I shall here quote the following from Moggridge (loc. cit., p. 122):—

Certain nests which were furnished with two doors of the cork type were observed by Mr. S. S. Saunders in the Ionian Islands. The door at the surface of these nests was normal in position and structure, but the lower one was placed at the very bottom of the nest, and inverted, so that, though apparently intended to open downwards, it was permanently closed by the surrounding earth. The presence of a carefully constructed door in a situation which forbade the possibility of its ever being opened seemed, indeed, something difficult to account for. However, it occurred to Mr. Saunders that, as these nests were found in the cultivated ground round the roots of olive trees, they may occasionally have got turned topsy-turvy when the soil was broken up. The spider then, finding her door buried below in the ground and the bottom of the tube at the surface, would have either to seek new quarters or to adapt the nest to its altered position, and make an opening and door at the exposed end. In order to try whether one of these spiders would do this, Mr. Saunders placed a nest, with its occupant inside, upside down in a flower-pot. After the lapse of ten days a new door was made, exactly as he had conjectured it would be, and the nest presented two doors like those which he had found at first.