Part 5

It has been demonstrated that these little creatures distinguish colors and select a special shade of colors for a background of the marvelously constructed webs. If the observer changes the colors surrounding the web, the Spider inhabitant at once seeks a new location and builds a new web. Spiders must have a sense of light and shade, in order to conceal their webs as they do, and in the case of the so-called “trap-door” variety, to camouflage the cleverly constructed hinged entrances to their tunnel homes so as to resemble their surroundings.

The olfactory pores of both Spiders and Insects are widely scattered over the body, head and appendages. The more highly developed the Insect, the more they are arranged in groups, “most of the groups being found on the legs, wings and mouth parts. So far only a few olfactory pores have been found on the antennæ, these being present on the bases of the antennæ of Bees, Grasshoppers, Roaches and Crickets. Briefly described, an olfactory pore is nothing more than a nerve passing through a tiny hole in the ‘skin’ or chitin of the Insect” (McIndoo, Loc. cit., Page 470). “The so-called gustatory sense in Insects is only a phase of the olfactory sense.”

Spiders, according to the latest experiments, are deaf, and only a few are able to make sounds. Most Insects can hear, but the Cicada is said to be deaf, and the female both deaf and dumb. Modern research tends to support Forel’s conclusion that Insects cannot “hear” in the sense that we do. He compares this perception in them to that in deaf-mutes who feel the rolling of a carriage at a distance. But nothing final can at present be said on this question. Schon, for instance, has described a structure in the tibiæ of Bees which he regards as an auditory apparatus. Child thinks that he has discovered an auditory organ in the Mosquito. Many of the experimental results obtained “indicate that Insects can hear” (McIndoo).

The orb-weaving Spiders have no peers in the art of weaving. They know how to fasten marvelously regular webs between the branches of trees, how to pass over rivers on bridges of floating threads, and even when still young, they know how to use similar threads to take flight through the air as real aeronauts.

“The most difficult but not the most delicate work in the making of an orb-web,” says Prof. E. L. Bouvier, “is the establishment of the suspending cable which stretches between two points at a distance from each other and supports the whole structure. Sometimes the Spider fastens its thread at one of these points and then repairs to the other where it stretches and fastens the cord which has issued from its spinnerets during the course of its journey. But this process is not applicable over all sorts of terrain and is even practically impossible when the two points are separated by a stream of water or by any other insurpassable obstacle. In this case the Spider stations itself or suspends itself at one of the points ... and emits a thread which is carried by the wind until it attaches itself at another elevated point. According to Fabre the process may differ somewhat, however: the Spider may suspend herself but soon thereafter reascends by her thread; the latter then forms a loop which is stretched out and fastened by the wind as in the preceding cases. In any case the Spider knows quite well when the attachment has occurred. She then stretches her cable and runs back and forth across it several times in order to multiply the number of threads and thus render the cable more firm. The next thing is to establish another side to the framework: the Spider suspends herself again, then reascends by means of her thread, follows the cable to the opposite end, and then seeks a suitable point further down where she stretches and fastens the thread emitted in the course of the journey.

“In the same manner, or by simply walking from one point to another, a diagonal thread is established which serves as the first radius of the web. Upon this diagonal line a point is chosen to be the center of the structure; the Spider attaches a second radius at this point and then proceeds to walk to the framework where she fastens the other extremity, after which she returns in the opposite direction to stretch this thread and make of it a definite radius; the excess length is reserved at the center to form a cushion. Now at one side and now at the other, in order to render the structure more stable, the Spider attaches new radii by the aid of those already established. When finished the radii are spaced at equal distances; they vary in number according to the species; Fabre counted twenty-one in the angular Epeira and thirty-two in the fasciated Argiope.

“Resting upon the cushion the Spider now revolves repeatedly about her own axis, attaching to the radii a central helix whose inter-radiary elements are straight lines. Then she advances a little farther and begins to establish a second similar helix which extends to the framework. This second helix is permanent in the Nephilæ and temporary in the Argiopæ, the Epeira and most other forms. Since it consists of cylindrical threads it is not very suitable for purposes of capture. Consequently as soon as it has carried it to the framework the animal returns along this helix, placing between its spirals a new helix whose elements are composed of threads bearing sticky globules. This helix constitutes a marvelously effective trap. In establishing it the Spider takes for a support and scaffold the auxiliary helix; but as the work proceeds the latter is destroyed except among the Nephilæ, in which it is retained to give more solidity to the structure.”

Professor Bouvier does not credit the Arachnoidea with much intelligence, and such as they possess he thinks is probably dominated by a strict automatism. Yet he asks, “Is it possible to ascribe to pure automatism or to mere reflex action so judicious a bit of architectural scaffolding? Undoubtedly the psychology of Spiders offers a vast field for observation and experiment.”

It is clear that the Spider is an amazingly good judge of distance, and “can draw parallel lines or converging lines with the accuracy of a draftsman who uses a drawing board and measuring instruments.” It is also certain that they form memory associations and learn by experience: “many examples show that they display a certain degree of discernment when they establish the bases of their shell or nest. And it is by making use of these faculties that they have been able to display plasticity in their habits and undergo an evolution in their industries.

At the present time they are doubtless quite as capable of evolution as in former times, but this tendency escapes our notice because of the automatism which dominates it. We are particularly struck by the extraordinary rôle played by touch in their automatic manifestations. Spiders nearly always perform their labors at night and it is merely by touch that they are able to recognize whether their cables are sufficiently taut, their radii properly spaced, and the spirals of the helix regularly placed. With their legs and their palps they search for contacts and measure distances and the sensitiveness of the spinnerets reveals to them the moment when their silken thread is properly attached. They seem to work as if blind, being largely guided by simple tactile reflexes” (Bouvier).

Says the same authority: “The Avicularidae and the closely related Atypus possess in a very high degree the skill of the miner; they also know how to construct masonry, for before weaving for their retreat an envelope of silk they rough-coat it and make it impermeable by means of a mortar made of earth and saliva.... Fabre has likewise studied the manner in which the Lycosa of Narbonne builds the bastion which surrounds the opening of its burrow. It forms it ‘of little pebbles, bits of wood, scraps of dry leaves, etc., the whole dexterously interlaced and cemented with the silk.’ And again it is the chelicerae which are employed. Many Lycosas, especially among the American species, perform similar labors. McCook reports (1889) that the Lycosa arenicola builds a bastion in the form of a chimney with small bits of straw or wood and that ... at the base of this edifice it builds a little wall of grains or quartz. More skillful still, the Lycosa carolinenses executes a neat bit of basket work; it curves, interlaces and fastens pine needles, so as to form a sort of bastion in the shape of a bird’s nest upside down.”

In discussing the mystery of the Spider’s web-weaving dexterity, Prof. J. Arthur Thomson, in his chapter on “Animal Intelligence,” (“The Outline of Science,” vol. 2) says:

“To credit animals with reason, which means experimenting with general ideas, is, in all probability, too generous. To try to reduce them to the level of automatic machines is certainly too stingy. The fact is that the behavior of animals is often intelligent, often instinctive, and often a subtle mingling of the two. But it is necessary to attach precise meanings to these terms.

“A young Spider, which never made a web before, may make its masterpiece true to the specific pattern the very first time. It does it without any model to copy, and with no trace of the prentice hand. Sometimes it can make the web in the dark, or in the course of a forenoon. This is instinctive behavior, depending on hereditary prearrangements of nerve-cells and muscle-cells, though never without its psychical aspect--a suffused awareness and a background of endeavor. But apart from theory, the fact of observation is certain that inexperienced animals suddenly blossom out into extraordinary intricacies and niceties of behavior, perfect the very first time, not requiring to be learned. This is instinct.”

“With reference to the intelligence of Spiders,” remarks Mr. Garrett P. Serviss, “I find among Mr. Belt’s records an account of the terrible panics caused by the advance of armies of Ants through the forest, all sorts of Insects fleeing wildly before them. But a Spider sometimes escaped by running out to the end of a branch and suspending itself from a single thread of silk, between the enemies above and the enemies below.

“There is exhibited an extraordinary repugnance by many people against admitting that any living being on this earth has been furnished with anything in the slightest degree resembling the peculiar gifts that assure to our race its immensely superior status. This seems to me a petty jealousy. When we dissect the motives of the human heart do we discover any reason why Man should be the exclusive possessor of sparks of Divine light?”

FOOTNOTES:

Cambridge Natural History, IV (1909).

McIndoo, Dr. N. E., “The Senses of Insects,” Annual Report Smithsonian Institution for 1920, Washington, 1922.

Scientific American, February, 1920.

BEETLES

Although the Burying Beetles (Necrophorus) live an isolated life, generally speaking, they know how to call for help when it is needed, and their appeals for assistance never go unheeded. As is well known, they must have some decaying organic matter to lay their eggs in, thus providing their larvæ with food. But the food must not decay too rapidly, and in order to slow up the process of decay the Beetles bury the corpses of all kinds of small animals.

Occasionally they find the corpse of a Bird or Mouse, which is too heavy for them to “handle” unaided. They thereupon call on their fellow Beetles for assistance, and from four to ten Beetles respond. Uniting their efforts they transport, if necessary, the corpse to a suitable soft ground, where together they bury it. When Gladitsch attached a dead Bird to a cross made out of two sticks, or suspended a Toad to a stick planted in the soil, “the little Beetles would in the same friendly way combine their intelligence to overcome the artifice of Man.” The same evidence of intelligent mutual aid has been noticed among the Dung-beetles.

WASPS

Not many years ago it was confidently asserted that “Man is the only tool-using animal.” Now we know that not only do members of the Ape family employ sticks for weapons and even for crowbars, and also use various objects for missiles, but even in the Insect world we find a creature, the Solitary Wasp (Ammophila), which makes a door of soft earth for its nest and then picks up a small pebble in its mandibles and hammers the edges of the door more securely, just as a man would use a pounding-iron. This phenomenon, observed by the Peckhams in 1898, has been verified by other investigators.

“Before we could recover from our astonishment at this performance,” wrote these now famous observers, “she had dropped her stone and was bringing more earth, and in a moment we saw her pick up the pebble and again pound the earth into place with it. Once more the whole process was repeated, and then the little creature flew away.”

Professor Thomson came to the conclusion that the Wasp’s use of the pebble for a mallet “is not part of the instinctive routine but is an individual touch, probably with more vivid awareness than is associated with the rest of the agency. The difficulty is to think of the origin of either the routine or the finishing touch without postulating intelligence or at least some appreciation of significance.”

Bouvier points out that the use of the little stone is not yet a fixed habit with Ammophila urania, belonging “only to certain individuals more highly endowed than others, and is perhaps only accidental even with them. Maybe it will finally pass into the instinctive habits of the species; for the present it belongs to the domain of individual intelligent acts.”