sembling a piece of silver ribbon, deeply indented on its edges, and consisting of equal triangles placed end to end; so that the angles of those that followed, were supported by the base of those which preceded, the whole moving round with incredible velocity. This spectacle was caused by the wings of the insects, which alone could be distinguished. Each of these flies, after having described one or two orbits, fell to the earth, or into the water, though not in consequence of having been burned."* Nothing could more distinctly indicate extreme delight, which seemed to end only when the joyous beings ceased to feel.

SIXTH WEEK-FRIDAY.

THE BUILDING SPIDER.

FROM considering the transformations of the insect tribes, we ascend to the instincts and habits of those varied and interesting families; and the first of these, which I shall select for examination, is the spider. There are several species of this remarkable insect, most of them possessing some peculiarity of habits, or organization, by which they are distinguished; but among these, there is none either more singular, or better calculated to exhibit a proof of Designing Wisdom, in its instincts, than that class which has acquired the appropriate name of the trapdoor or building spider. I shall follow the account of the celebrated M. V. Audoin, as abridged by Mr. Kirby in his Bridgewater Treatise.†

Some species of spiders, M. Audoin remarks, are gifted with a particular talent for building: they hollow out dens; they bore galleries; they elevate vaults; they build, as it were, subterranean bridges; they construct, also, entrances to their habitations, and adapt doors to them, which want nothing but bolts; for, without any exaggeration, they work upon a hinge, and are fitted to a frame.

* Reaumur, Mem. vol. vi. p. 485.

+ Vol. ii. pp. 287–293.

The interior of their habitation, he continues, is not less remarkable for the extreme neatness which reigns there; whatever be the humidity of the soil in which they are constructed, water never penetrates them; the walls are nicely covered with tapestry of silk, having usually the lustre of satin, and almost always of a dazzling whiteness. He mentions only four species of the genus as at present known ;-one which was found in the island of Naxos; another in Jamaica; a third in Montpelier; and a fourth, that which is the subject of his Memoir, in Corsica; to which I may add a fifth species, found frequently by Mr. Bennett, in different parts of New South Wales.

The habitations of the species in question are found in an argillaceous kind of red earth, in which they bore tubes about three inches in depth, and ten lines in width. The walls of these tubes are not left just as they are bored, but they are covered with a kind of mortar, sufficiently solid to be easily separated from the mass which surrounds it. If the tube is divided longitudinally, besides this roughcast, it appears to be covered with a coat of fine mortar, which is as smooth and regular as if a trowel had been passed over it. This coat is very thin, and soft to the touch. But, before the adroit laborer lays it, she covers the coarser earthy plaster-work with some coarse web, upon which she glues her silken tapestry.

All this shows, that she is directed in her work by a wise Master; but the door that closes her apartment is still more remarkable in its structure. If her well was always left open, she would be subject to the intrusion of guests, that would not, at all times, be welcome or safe. Providence, therefore, has instructed her to fabricate a very secure trap-door, which closes the mouth of it. To judge of this door by its outward appearance, we should think it was formed of a mass of earth coarsely worked, and covered internally by a solid web; which would appear sufficiently wonderful for an animal that seems to have no special organ for constructing it; but, if it is divided vertically, it will be found to be a much more complicated fabric than its outward aspect indicates,

for it is formed of more than thirty layers of earth and web, emboxed, as it were, in each other, like a set of weights for small scales.

If these layers of web are examined, it will be seen that they all terminate in the hinge; so that the greater the volume of the door, the more powerful is the hinge. The frame in which the tube terminates above, and to which the door is adapted, is thick, and its thickness arises from the number of layers of which it consists, and which seem to correspond with those of the door; hence the formation of the door, the hinge, and the frame seem to be a simultaneous operation, except that, in fabricating the first, the animal has to knead the earth, as well as to spin the layers of web. By this admirable arrangement, these parts always correspond to each other, and the strength of the hinge, and the thickness of the frame, will always be proportioned to the weight of the door.

The more carefully we study the arrangement of these parts, the more perfect does the work appear. If we examine the circular margin of the door, we shall find that it slopes inwards, so that it is not a transverse section of a cylinder, but of a cone; and, on the other side, that the frame slopes outward, so that the door exactly applies to it. By this structure, when the door is closed, the tube is not distinguishable from the rest of the soil, and it is doubtless for the purpose of effecting this concealment that the door is formed with earth. Besides, by this structure, also, the animal can more readily open and shut the door. By its conical shape, it is much lighter than it would have been if cylindrical, and so more easily opened; and, by its external inequalities, and mixture of web, the spider can more easily lay hold of it with its claws. Whether she enters her tube, or goes out, the door will shut of itself. This was proved by experiment; for though resistance, more or less, was experienced when it was opened, when left to itself it always fell down, and closed the aperture. The advantage of this structure to the spider is evident; for whether it darts out upon its prey, or retreats from an enemy, it is not delayed by having to shut its door.

The principal instruments by which this little animal performs her various operations, are her mandibles and her spinners. The former, besides the two rows of tubercles, between which, when unemployed, her claw or sting is folded, has, at the apex, or their inner side, a number of strong spines. As no one has ever seen her at work upon her habitation, it cannot be known exactly how these organs are employed in her various manipulations; but she probably makes use of her anterior legs along with them.

Though the particulars I have here stated, of the history and habits of these subterranean spiders, demonstrate, in every respect, as far as we know them, the adaptation of means to an end, far above the intelligence of the animal that exhibits them; yet, fully to appreciate the wisdom, power, and goodness that created her, and instigated her to exercise these various arts, and to employ her power of spinning webs in building the structures necessary for her security, as well as for the capture of her prey, we ought to be witnesses to all her proceedings, which would probably instruct us more fully why she forms so deep a tube, and one so nicely covered with a peculiar tapestry from the mouth to the bottom.

SIXTH WEEK-SATURDAY.

SPIDER'S WEB.

THE power which the various races of spiders possess of spinning webs to entrap their prey, is well known; but there are some curious particulars connected with this subject, which, though not so generally understood, are exceedingly interesting.

This little animal is devourer of flies and other insects, and seems to be intended by the Creator to fulfil the important part of preserving the balance in that department of the animal creation with which it is con

nected, by keeping in check the tendency to multiply to an inconvenient degree. In all the orders of living beings, such a provision is made, from the lion and hyena which roam the forest, spreading carnage and desolation around, to the invisible tyrant of the infusory tribes, which the solar microscope has disclosed, called, on account of its insatiable voracity, the water-tiger. To accomplish this useful object, the spider is endowed with peculiar properties as well as instincts, the most remarkable of which, is that of preparing and spreading nets to ensnare her prey.

The manner in which the material is formed for the fabrication of her net is as follows. Immediately below the end of the body, planted in a roundish depressed space, are six jointed teat-like organs. Four of these are pierced with a multitude of holes, so numerous, and so extremely fine, that there are, in some species, above a thousand in each of the divisions, a space itself not bigger than the head of a pin. From every one of the holes, a thread proceeds, so that the very finest part of the web, which we can scarcely see, is not a single thread, but a cord, composed of no fewer than four thousand strands, to use the technical language of the ropemaker. The line spun by the smallest spider, itself no bigger than a grain of sand, is so fine, that four millions of them, put together, would not exceed the thickness of a human hair; so that the number of strands which would be necessary to form a line of this thickness, would not be less than sixteen thousand millions. This is not more startling to a person unaccustomed to such investigations, than it is true.*

There is an obvious intention in the extreme minuteness of the original strands. Not only is the viscous. matter, of which the web is composed, by being exposed to the air in these exceedingly fine filaments, instantly dried, which seems necessary to its tenacity, but the line takes firmer hold, at the places where it is attached to

* [Nevertheless, we cannot help suspecting, that there must be some mistake in the calculation, owing to the exceeding minuteness of the subject of experiment, and that the statement of numbers is a greatly exaggerated one.-AM. ED.]