Very little, however, has been added to our knowledge of the life-history of these remarkable architects for several years past, and, indeed, I think it may be safely asserted that the study of the habits and interdependence of the members of the animate world has not, during the last fifty years, made anything like a corresponding progress to that which may be seen in classification and description. The microscope has led many who, a century ago, would have found their chief delight in observing those points in the habits and external characters of living creatures which the naked eye could readily seize upon, to look much closer, to anatomize and describe in detail every organism, great and small, and to examine every tissue and cell.

It is, however, to the materials now being amassed by these modern "cabinet naturalists" that recourse must be had if we wish to form a true comprehension of the functions and habits of living things. They must tell us, for example, what instruments, tactile and visual, an animal possesses if we wish to understand how it constructs a particular fabric, so that the "field naturalist" will have to apply to his brother of the "cabinet" before he can turn his observations to good account.

Still, the fact remains that the habits of plants and animals afford many openings for careful investigation, and such as are especially within the reach of those lovers of nature who have ample time at their disposal, and the opportunity to spend it in a warm climate where life abounds, and is never wholly checked even in the depth of winter. It seems strange to think that collectors so frequently take creatures out of wonderfully constructed nests and yet never observe, or at any rate never describe, the structure of these fabrics. Thus, for example, the dwellings of only eight out of the thirty-six species of trap-door spider stated by Prof. Ausserer[46] to belong to the Mediterranean region are known in books, those of the remaining twenty-eight being, as far as I have been able to learn, yet to be discovered. This is the more strange as from the nocturnal habits of these creatures it is almost always necessary to dig them out of their nests; indeed it is more than probable that if all the dwellings which have been destroyed had been described, the following pages would never have appeared.

Before proceeding to pass briefly in review what has been written on the subject of trap-door spiders, it will be well to take one glance at the relation which these spiders bear to their fellows. The great order of spiders (Araneæ) has recently[47] been divided into seven sub-orders, the fourth of which, Territelariæ, includes all the trap-door spiders, and some others which do not construct trap-doors. This sub-order corresponds with that which was formerly called Mygalidæ, but this name, as well as that of Mygale, originally given to all trap-door spiders, has been abandoned because this latter name had previously been applied to a genus of Mammals, and it was feared that confusion might arise.

The Territelariæ [or underground weavers] are distinguished from all other spiders by the position of their falces,[48] which have the fang directed downwards, and move vertically parallel to one another. Thus when a victim is seized by one of the Territelariæ it receives a downward blow, while other spiders strike sideways, the falces moving in a horizontal or oblique direction. With very few exceptions this sub-order may also be known by the presence of four blotches of paler colour at the base of the abdomen underneath, indicating the position of four air-sacs, almost all, or indeed perhaps all, other spiders having but two.

Certain species of Territelariæ are the only spiders known to construct nests closed with a door, and these creatures must be admitted to rank among the first of Nature's handicraftsmen and inventors.

The geometrical webs of many common spiders are very beautiful structures, but these are for the most part only snares for prey, and not permanent dwellings, although the cocoons in which the eggs are placed are often most ingeniously contrived. Thus in the south we may sometimes find an inverted balloon of strong silk about an inch long attached to heath and other bushes, which, if examined during the winter, will be found to contain in its centre a case enclosing a mass of eggs about one-third the bulk of the entire cocoon. This inner case is shaped exactly like the outer, and both have a circular silk lid carefully closed, and the space between the two is filled with a dense mass of golden-brown silk, which acts no doubt as an excellent non-conductor. This cocoon is the work of Epeira fasciata, a species apparently only found in southern Europe.

Other spiders again, such as Theridion,[49] suspend by a long and delicate cord of silk a minute balloon, scarcely larger than a seed-pearl, containing their eggs, which sways to and fro in the lightest breath of air. But admirable as these cocoons and geometrical snares are, the homes of these and of spiders generally do not exhibit much contrivance or ingenuity, or cannot at any rate be ranked in the same category as those of the trap-door spider. But it may be asked, why should we admire the one more than the other, since it is clear that the most squalid and mean-looking nest exactly serves the purpose of its occupant, whether for shelter or defence, and in many cases a spider might even say with truth that as for her home it would not be so safe if it were not so dirty.

But the answer is simple: the trap-door spider's dwelling is to that of common spiders what the Mont Cenis tunnel is to other tunnels, and something besides.

What delights us is to see how by clever contrivance and great perseverance new and multiplied difficulties have been overcome, and dangers avoided, and the interest aroused is exactly proportionate to the amount of these difficulties and dangers.

It is hoped that the following pages and their accompanying illustrations will vindicate the claims of these spiders to the marked attention and admiration which is here asserted to be their due as architects and engineers.

There is but one British or North European representative of the Territelariæ—namely, Atypus piceus (or Sulzeri),[50] and this creature does not appear to deserve the name of trap-door spider, for in three nests which M. H. Lucas kindly showed me, preserved at the Jardin des Plantes at Paris, the mouth of the tube was destitute of any covering. I gathered from what I saw, and from what M. Lucas told me, that these nests [which he had taken in the neighbourhood of Paris], consist of a silk tube from eight to ten inches long, of which about one inch only at the lower extremity penetrates the earth, the remainder being carried upwards in an irregular and sinuous course among the stems and leaves of small plants and grasses to which it is attached. When the tube is removed from these supports it collapses, and appears like a rather coarsely woven ribbon-shaped strip of silk.[51]

Four types of trap-door nest, properly so called, may now be distinguished in the world at large, and these are represented diagrammatically in the following woodcut.[52]

Of these two only (A and B) were known up to the present time, the construction of which is much simpler than that of the two new types (C and D), which I have hitherto only found at Mentone and Cannes.[53]

It will be seen at a glance that A and B have but one door, while C and D have two, these latter having a surface door, and also another door a short way under ground.

All the nests consist of a tube excavated in the earth to a greater or less depth, unbranched in all but D, and in every case lined with silk, this lining being continuous with the lining of the door or doors of which it forms the hinge.

I have found it convenient to distinguish these four types of nests by the following names:—A, the single door cork nest, or shortly the cork nest; B, the single door wafer nest; C, the double door unbranched nest; and D, the double door branched nest.

The type B has only been found in the West India Islands, and is chiefly distinguished from A by having a thin and wafer-like door, wholly constructed of silk, without admixture of earth, lying on rather than fitting into the aperture of the tube; while in A the door is much thicker, made of layers of earth and silk, and so contrived that it tightly closes the mouth of the tube, which is bevelled to receive it, much as a cork closes the neck of a bottle.[54]

The West Indian nests are of a much tougher and coarser texture than those which I have seen in Europe, and vary somewhat in the shape of their tube, which is curved or straight, and sometimes has near its lower extremity a short spur-shaped enlargement, giving to the whole a ludicrous resemblance to a stocking, of which this spur is the heel.

Mr. Gosse,[55] in his Naturalist's Sojourn in Jamaica, has given an admirable description of one of these single door wafer nests, the work of Cteniza nidulans, which I cannot do better than quote:—

The nest is "cylindrical, or nearly so, from four to ten inches deep, and about one inch in diameter; the bottom is rounded; and the top, which is at the surface of the soil, is closed very accurately with a circular lid. They are not all equally finished, some being much more compact, and having the lid more closely fitted than others. Some have irregular bulgings, and ragged laminated offsets on the outer surface; but all are smooth and silky on the inside.... The mouth of the tube, and the parts near it, are very strong; the walls here often having a thickness of from one-eighth to one-fourth of an inch; but the lower parts are much thinner. The lid is continuous with the tube for about a third of its circumference, and this part may be called the hinge, though it presents no structure peculiar to itself; it is simply bent at a right angle, as is manifest, if a nest be cut longitudinally through with scissors, the incision passing through the midst of the lid. The mode of construction, I judge, from examination of many nests, to be this. The spider digs a cylindrical hole in the moist earth, with her jointed fangs or mandibles, carrying out the fragments as they are dislodged. When the excavation has proceeded a little way, she begins to spin the lining which forms the dwelling. I conclude thus, because nests are occasionally found a few inches in length, with the lid and upper part perfect, but without any bottom, these being evidently in the course of formation. I suppose that she weaves her silk at first in unconnected patches, against the earthy sides, perhaps where the mould is liable to fall in; and thus I account for the loose rough laminæ of silk that are always found projecting from the outer surface. These are overlaid with other patches more and more extensive, until the whole interior walls are covered; after which the silk is spun evenly and continuously all round the interior, in successive layers of very dense texture, though thin. Under the microscope, with a power of 220 diameters, these layers are resolved into threads laid across each other and intertwined in a very irregular manner; some are simple, varying from ¹/₇₀₀₀ to ¹/₂₀₀₀ of an inch in diameter, and others are compound, several threads, in one part separate, being united into one of greater thickness which cannot then be resolved.... The mouth of the tube is commonly dilated a little, so as to form a slightly recurved brim or lip; and the lid is sometimes a little convex internally, so as to fall more accurately into the mouth and close it.

"The thickening of the hinge by additional layers is, I think, accidental only, as, out of the many specimens that I have examined, only one or two had such a structure. In the neatest examples, the lid is of equal thickness throughout its extent, agreeing also with the walls for the first few inches of their depth."

Mr. Gosse says that he possesses one specimen of peculiar compactness, which differs from all the others that he has examined in having "a row of minute holes, such as might be made by a very fine needle, pierced around the free edge of the lid, and a double row of similar ones just within the margin of the tube. There are about fifteen or sixteen punctures in each series, and they penetrate through the whole substance, the light being clearly seen through each hole. I do not think, as I have somewhere seen suggested, that they are intended to afford a hold for the spider's claws when she would keep her door shut against the efforts of an enemy, for what would be the use of having them in the tube close to the lid, so close that not the eighth of an inch intervenes between the surface of the lid and that of the tube, when the former is tightly closed? I would suggest whether they may not be air-holes, for so tight is the fitting of the lid, and so compact the texture of the material, that I should suppose the interior would be impermeable to air but for this contrivance."[56] "The spider that inhabits this nest is black, with the thorax of an exceedingly lustrous polish, its abdomen is full and round, its legs very short."

Another form of this single door wafer nest is described by Mr. Sells,[57] in which there is a hinge-like thickening of the silk lining of the tube about an inch below the actual hinge of the door, which it is suggested may serve to give additional elasticity. This was not found, however, in all the nests examined, and Mr. Sells conjectures that in newly constructed nests the lid may close sufficiently firmly without this contrivance, and that it is only added in older nests.

Patrick Browne's figure, to which reference has been made above, represents a nest with two doors, one applied against the other, at the mouth of the tube, and it has often been asked what this could possibly mean.

Some have thought that the drawing was fanciful, others that it was made from an abnormal or injured nest. However, I believe that the drawing, though rude, is, in fact, not very incorrect, and shows a case of repair or enlargement of the nest, a subject to be treated of more fully further on. There is a specimen exhibited in the British Museum which in this respect very nearly corresponds with Browne's figure; it is labelled "Nest of Trap-door Spider with two doors, from the spider having enlarged its abode.—Jamaica." Here one sees that the spider has prolonged its tube about half an inch beyond the original mouth of the nest, where it has constructed a new mouth and door, the old door standing straight up at the back of and behind the new one.

I imagine that the explanation of this curious piece of cobbling may be somewhat as follows:—When the nest was in its original state and had but one door, this door became by some accident covered over with earth to about the depth of half an inch, and the inmate was thus imprisoned. Then the spider, being, like most other members of its order, very unwilling to abandon its home, determined to clear away the entrance to its nest, and to lengthen the tube so that it should reach up to the new level of the surface of the earth.... If I am right, this should rather be called a lengthening than an enlargement of the tube.

The nests of the cork type (A, p. 79) may usually be distinguished at a glance from those of the wafer type by the greater thickness of the door, and by its manner of shutting, but a nest from Morocco has been figured and described by Prof. Westwood,[58] which seems intermediate between the two. The door in this case may perhaps be considered as of the cork type, though it is very thin, for it does fit into the mouth of the tube, which is bevelled to receive it.

These nests were forwarded with their living occupants (Cteniza [Actinopus] ædificatorius) from Tangiers to Prof. Westwood, who describes the nests as being "about four inches deep, slightly curved within, about three quarters of an inch in diameter, the valve at the mouth not being circular, but rather of an oval form, one side where the hinge is placed being straighter than the other. The valve is formed of a number of layers of coarse silk, in the upper layers of which are imbedded particles of the earth, so as to give the cover the exact appearance of the surrounding soil, the several successive layers causing it, when more closely inspected, to resemble a small flattened oyster-shell."

The resemblance between this nest and that of the West Indian species is the more interesting as Prof. Westwood says that both belong to the same genus, (Cteniza or Actinopus of different authors,) and are so closely allied as to present scarcely any important distinction but that of size.

We shall find, however, on comparing the nests of these trap-door spiders and their occupants, that we cannot as yet make any rule as to the kind of nest which we may expect from a given spider.

It will be seen that species belonging to the same genus, and closely resembling one another, sometimes build dissimilar nests; while others, belonging to different genera, and unlike in many important respects, construct almost identical nests.

This is the more strange, because, if we examine the structure of the claws and palpi, they often seem to be specially adapted to serve as carding instruments and to play a very important part in the weaving of the silk linings of the nest; and yet nests of the same type are occasionally produced by spiders in which these appendages are quite unlike, and dissimilar nests where the claws and palpi are to all appearance identical.

Thus, for example, if the reader will examine the drawings of part of the foremost right foot of Cteniza fodiens, figs. A, 9 and 10, Plate VII., p. 88, with that of Nemesia cæmentaria, figs. A, 9 and 10, Plate VIII., p. 94, both of which make nests of the cork type, he will see that in the former the last joint of the tarsus is armed along the inner side, with many moveable spines, and that each of the two curved terminal claws has only one very strong tooth near the base; while the same joint of the latter (N. cæmentaria) has no spines, and the claws have three minute comb-like teeth near the base.

On the other hand, in the reverse case, where the structure of the same joint is very similar, the nests may be wholly unlike, as in Nemesia Eleanora, Plate XII., p. 106, and N. cæmentaria, Plate VIII., where the nest of the former is of the double-door unbranched type, and that of the latter of the single-door cork type.

It is probable however that a fuller and closer comparison of, and a more exact acquaintance with the several parts and their functions might show us that all spiders which spin similar webs are furnished with equivalent instruments, so that what one leg lacks another may possess in some shape or another; brushes of stiff hairs in one place, compensating for a toothed claw, or for a row of moveable spines in another.[59]

It would be interesting, from this point of view, to draw all the parts which may be supposed to aid in the act of weaving, and so to contrast the corresponding limbs of different spiders, the nests of which are known, that one might see at a glance in what they differed and agreed. I have done this for the falces and the last joint of the foremost right foot of the four spiders figured in Plates VII., VIII., IX., and XII., but to make the case complete all the limbs should be represented in the same way.

Of the two spiders which are shown with their cork nests in Plates VII. and VIII., the purplish grey Cteniza fodiens, (Plate VII.) appears to be much rarer than the brown striped Nemesia cæmentaria (VIII.), at any rate at Mentone. I have hitherto only succeeded in obtaining four specimens of the former, though I have searched repeatedly for them at Cannes and Mentone, while the latter species is tolerably common.

The nests are, however, often extremely hard to find, and in some cases it is only by chance that I have been able to light upon them. All these trap-door spiders seem usually to prefer rather moist and shady places, and sloping banks or loose terrace walls where the interstices between the stones are filled up with earth, and concealment is afforded by the creeping lycopodium (Selaginella denticulata), Ceterach, spleen-wort or maiden-hair ferns, with short moss and splashes of white lichen to distract the eye.

It was from such a terrace wall at Mentone, on March 26, 1872, that the nest A in Plate VII. was taken, the tube running obliquely back into the earth between the stones, and the door being concealed by a net-work of lycopodium, one spray of which had been allowed to grow on its upper surface.

The tubes of these as of the other kinds of nest are sometimes straight, but more frequently they are bent, and almost always take a downward course.

The following is Mr. Pickard-Cambridge's description[60] of Cteniza fodiens, the spider which constructs this nest.

FAM. THERAPHOSIDES.

Gen. Cteniza, Latr.

The portions of nests at B and C in Plate VII. also belong to Cteniza fodiens, the latter being very similar to A in its surroundings, but having a rather thinner door, slightly hollowed out above (C 1). The smaller nest shown shut at B and open at B 1,[61] is admirably concealed by mosses and lichens, some of which actually grow upon the door, and here two minute trap-doors, belonging to infantine examples of a distinct species of spider (Nemesia meridionalis), are seen on the left hand below.

It is not rare to find small colonies of nests of the same or distinct species grouped closely together in this way, though I greatly doubt whether one can safely assume their sociability from this fact.

I have very seldom seen nests on the flat ground, where the door would lie horizontally when closed, a sloping or nearly vertical bank being usually chosen, where the door will fall to by its own weight.

In the Ionian Islands another species or variety of Cteniza, described under the name of Cteniza (or Mygale) ionica, and represented as being of an uniform yellow-brown colour, is said to make its nests in the earth of the terraces round the roots of the olive trees.

Mr. Saunders[62] gives admirable figures and descriptions which show us at once that these nests, which he discovered in rather elevated situations in the island of Zante, are of the cork type; but, in this case, the entire door does not shut flush with the surface, as in ordinary cork nests, but has a short spur-like projection above and behind the hinge, serving, as is conjectured, like a lever, by pressing on which from the outside the lid may easily be raised.[63] When I come to speak of the manner of constructing and repairing nests I shall have occasion to refer to these nests again.

I have not as yet found any nests on the Riviera which can be said to correspond accurately with those of Ct. ionica, the only builders of cork nests yet discovered in this district being Cteniza fodiens and Nemesia cæmentaria.

This latter species is described by Mr. Pickard-Cambridge,[64] in the following terms:—

Gen. Nemesia (Savigny).

The cork nests are the simplest form of nest, with the exception of those described above from Jamaica, and have constituted, up to the present time, the only type known in Europe. Their chief claims to our admiration lie in the perfection of workmanship which the doors usually exhibit, and the marvellous concealment which they afford when closed. These doors as a rule fit so tightly [thanks to the accurate adjustment of their sloping sides to the bevelled lip of the tube which receives them,] that they afford a certain amount of mechanical resistance, even when the spider is away. But, after examining a very large series of these cork nests, I find that there is some variation in the degree of perfection attained in their work by different individuals of the same kind. The mechanical resistance is greater or less in proportion to the thickness and weight of the door, and to the slope of its sides, and of the bevelled edges of the tube; and in each of these details a marked difference may be observed.

One might suppose from what has so often been repeated as to the habits of N. cæmentaria, that, whenever any one attempts to open the door, the spider, which is always at home in the day time, would dart up from the bottom of the tube and endeavour to keep it closed by holding on from within.