Homes Without Hands: Being a Description of the Habitations of Animals, Classed According to Their Principle of Construction - Page 108

Differing as they do in shape, color, and material, they have one object in common, namely, the rearing of the young. They are clearly nests in the true sense of the word, being devoted not to the parents, but to the offspring. At the upper part of the illustration may be seen a number of long, spindle-shaped bodies, suspended from a branch. These are drawn about half the full size, in order to allow other specimens to be introduced into the same illustration for the purpose of comparison. In color they are nearly white, with a slight yellowish tinge, and are very soft and delicate of texture, so that when viewed in a good light they form a very striking group of objects.

In the opposite upper corner of the illustration may be seen a remarkable nest, which few would recognize as the work of a spider. Such, however, is the case, the creature being urged by instinct to take several concave seed-pods, and to fix them together as seen in the drawing. The seed-pods are fastened firmly together with the silken thread of which webs are made, and in the interior the eggs are placed. The drawing is reduced about one third in proportion to the actual object. Several of these singular nests are in the collection at the British Museum.

Occupying the lower part of the illustration is seen a leaf upon which are piled a number of fragments of leaves, so as to form a rudely conical heap. This is also the work of a spider, and is made with even more ingenuity than the two preceding specimens. In the first instance the spider has spun a hollow case of silk, similar in principle of construction, though not in form, to the spherical egg cases made by several British spiders. In the second instance the creature has chosen a number of concave seed-pods, and, by adjusting their edges together and fastening them with silk, made a hollow nest, which only requires to be lined in order to make it a fit nursery for the young. But, in the present example, the work of nest-making has been much more elaborate, for the structure has been regularly built up of a great number of pieces, each being arranged methodically upon the other, very much as children in the streets build their oyster-shell grottoes. The labor must have been considerable, even if the spider had nothing to do but to arrange and fasten together pieces of leaves which had already been selected.

Tufted Spider.

Spherical Spider Nests.

THE large, oval, cocoon-like nests which are seen in the accompanying illustration are made by the TUFTED SPIDER of the West Indies, a creature which derives its name from the remarkable tufts of stiff, bristle-like hairs which decorate the limbs. A very fine specimen of this remarkable Spider is now before me, having been taken out of its bottle with extreme difficulty, owing to the great length of the limbs, and the weight of the prolonged abdomen.

The length of the body is one inch and a half, of which measurement the abdomen alone occupies two thirds. The average circumference of the abdomen is five sixths of an inch; and, as it varies very little throughout its entire length, that portion of the body is very solid and heavy. The color is deep chocolate-brown, curiously marked with circular dots of bright yellow, and farther diversified with stripes of the same color, especially over the fore part of the abdomen. Two bold yellow bars are also drawn transversely across the under surface of the abdomen. The thorax is deep brown, and clothed with short hairs of grayish-yellow, set so densely that the dark color of the thorax can not be seen without close inspection. There are, however, three black squared spots on each side, and a black spot occupies the centre. The animal is armed with a formidable pair of poison-jaws, of a deep shining black, at the ends of which the curved fangs are bent inward like the venomous teeth of the rattlesnake. On the front of the thorax, and looking directly forward, are the eight eyes, the four smallest being arranged closely together in the centre, in the form of a square, and the four largest being set on bold prominences so as to form a large oblong, in the centre of which is the square.

The limbs are of considerable length. The first pair of legs, which are the longest, measure two inches and a half in length, and the expanded second pair measure four inches and a half. The most remarkable point about the spider is the peculiarity from which it derives its name. The first, second, and fourth pairs of legs are adorned with dense hairy tufts, the first pair having two tufts each, and the others only one. The third pair of legs are much shorter and smaller than the others, and are destitute of tufts. As the legs themselves are bright yellow-brown and the tufts are deep black, the contrast of color is very bold and agreeable to the eye. The entomological reader may perhaps remember that social exotic beetles are also decorated with tufts upon their antennæ and limbs. Of the curious spherical spider-nests, with their black cross-bars, nothing is known except the mere fact of their existence. They are about as large as full-sized black currants.

In the following illustration three most remarkable nests are given, all of them the work of hymenopterous insects, and all serving in some degree to illustrate the hexagonal system of cell-building, so common among the Hymenoptera.

Of these, perhaps, the central figure is the most interesting, because it entirely sets at rest a question which is periodically agitated. It is made by an insect belonging to the genus Icaria. Perhaps my readers may remember that on page 450 the celebrated bee-cell problem is described, and that mention is made of the many theories which have been invented to solve the riddle. Among them the two most conspicuous are those which are known as the equal pressure theory and the excavation theory. Differing as they do in many respects—one attempting to prove that each cell is forced into the hexagonal shape by the pressure of six cells surrounding it, and the other that the cell is made hexagonal by the cutting away of material from six surrounding cells—they both agree in one point, namely, that the normal shape of the cell is cylindrical, and that it only assumes the hexagonal form by mechanical means.

Mischocyttarus.

Icaria.

Raphigaster.

These questions were briefly mentioned, because an entire omission of them would appear negligent, but they were not followed up because the nests that would set them at rest belonged to another group. We will first take the central nest.

The specimen from which this was drawn was fortunately in an unfinished state, only eight cells being made, and some of these but partly finished. As the reader may see by reference to the illustration, all the cells are hexagonal, whether finished or incomplete, and, moreover, that the edges of the hexagon are quite sharp and well defined.

Now, if either of the two theories were true, the cells would not have assumed this shape. Where are the six surrounding cells that are needed to compress the outermost cell into an hexagonal? Or where are the six surrounding cells from which the hexagon was excavated? There are none. The outermost cell, for example, is perfectly free on five of its sides, being only attached to the neighboring cell by the sixth side. Compression, therefore, has not been employed, because there is nothing that can compress it; neither has excavation been used, because there is no material to be excavated. No one, on looking at this group of cells, can deny that the hexagonal form is produced by the direct labors of the insect, and not by any secondary mechanical means.

Perhaps some one who has not examined the actual object might say that the materials of which the cells are made are sufficiently stiff to need no support of contiguous cells. Now the substance of this remarkable nest is singularly slight, the walls being not thicker than the paper on which this account is printed, and the material is quite soft, as may be seen by the curvature produced by the mere weight of the structure. Yet none of the cells are united by more than three sides, the greater number by two only, and the external cells merely by a single side, leaving five sides and four angles perfectly free.

In this particular specimen the material has evidently been varied, the insect having been forced to employ different substances in forming its home, as is seen by the pale and dark rings alternately surrounding the cells. The insect which makes this curious home is of moderate size, and is grayish-black, banded with yellowish-white. The abdomen is tolerably stout and sharp-pointed, and is attached to the thorax by a short brownish foot-stalk. This insect is a native of Natal. Other species of the same group will be mentioned in the course of the following pages.

In the left-hand upper corner may be seen a very remarkable triple nest depending from a branch. This is the work of an insect called Mischocyttarus labiatus, which belongs to the family Polistidæ. Like the nest of the preceding insect, it is attached to the bough by a slender and tolerably long foot-stalk, and the mouths of the cells are downward, as is always the case with these insects.

Generally the group of cells is single, but occasionally a more perfect nest is found, which, like the specimen figured in the illustration, has three distinct cell groups, each pendent from the centre of the group above. This may seem rather a dangerous method of suspending the nest, but it is not more so than that which is employed by the common wasp, which builds tier under tier of cells, hanging each tier from its immediate predecessor by little pillars of the same paper-like material as that of which the cells are constructed; or very much, indeed, as the roadway of a suspension bridge is hung from its arch instead of being placed upon it. The insect itself is smaller than the preceding, and is almost uniformly brown.

THE last of these three groups is particularly entitled to notice, on account of its bearing upon the hexagonal principle, which has been so often mentioned. The name of the insect is RAPHIGASTER GUINIENSIS, and, as its name implies, it is a native of Western Africa.

The nest consists of a group of long cells, and is suspended from a foot-stalk. The material of which the nest is composed is peculiarly soft and flimsy, reminding the observer of the worst and most porous French paper. The cells are so thin that the light shines through their delicate walls, and they are so soft that they yield to the least pressure. Each cell is small at the base, and increases regularly toward the mouth like a reversed sugar-loaf.

Now, if the real cause of the hexagonal form were to be found in the equal pressure of surrounding cells, the central cells of this group ought to be hexagons, for they are soft, pliable, and their conical form renders them peculiarly liable to be squeezed out of shape. Yet, on examining the nest, we find that all the cells retain their conical form, the central cells being as rounded as those on the exterior, and their mouths being as circular.

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