Art. XLII.—Description of Trap-door Spiders' Nests from California and from Western Australia in the Christchurch Museum.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 10, 1877, Page 301

Art. XLII.—Description of Trap-door Spiders' Nests from California and from Western Australia in the Christchurch Museum. By. R. Gillies, F.L.S. Plate XIII. [Read before the Otago Institute, 9th October, 1877.] In November last, when in Christchurch, I had the opportunity, through the kindness of Dr. Haast, of examining four trap-door spiders' nests from California and two from Western Australia, which are deposited in the Canterbury Museum, and which I was informed have never been examined or described. Each nest or trap-door has special features of its own which I will point out afterwards, but there is a very marked distinction between the Californian nests and the Western Australian, and between each of them and our New Zealand species. The Californian nests have all thick doors bevelled at the edge, and fitting tight into the mouth—the outside of the trap-door being level and coincident with the surface around—they are, in fact, true “cork nests.” The South Australian ones have the mouths of the nests raised above the surface around; they are really on little hillocks or protuberances of the ground and have the trap-door fitting on to the top of the mouth as a cap overlapping all round and raised in the centre like miniature tea or coffee-pots with lids to them. A reference to my paper on the New Zealand species* Trans. N.Z. Inst., VIII., Art. XXXI. will show that they are quite different from either of these types. In that paper I stated that I was inclined to think the distinctions laid down by Moggridge between cork nests and wafer nests did not hold good so far as the Oamaru species is concerned. My examina tion of these nests has revealed to me that what Moggridge referred to as cork nests was something quite different probably from what I understood. The distinction between cork nests and wafer nests rests mainly on the thickness of the door, and as he gives no measurements as a guide, I fell into the mistake of thinking that the extremes of the thicknesses would be within reasonable limits as compared with the size of the nest, and hence I said that “doors of all degrees of thickness are to be found and that this distinction does not hold good.” I find now that these Californian nests have their doors so excessively thick in proportion to their size as at once to justify the distinction of cork nests, and therefore that our New Zealand species, with all their varying thicknesses of door, are all wafer nests. These foreign nests, now about to be described, are also very much shorter than those of our New Zealand species, and in this they approach more nearly to the Jamaica nest in our own museum, and described at the end of my paper mentioned above. It is believed that the ultimate classification

of trap-door spiders will depend largely on the type of nest which they construct. It is therefore of much more importance than might at first appear, to have full and correct descriptions of nests, and this must be my apology for the somewhat minute detail which I shall now enter upon. In a question where the principles of classification are still undetermined, it is obviously impossible to say what is of value and what is not. It is, how- ever, greatly to be regretted that, as in the case of our Jamaica nest, the ingenious constructors of the nests, now about to be described, have been lost, or destroyed by insects, and hence it is now impossible to connect these nests with any particular species of trap-door spider. Nests from California. No. 1 is in soil of red volcanic clay or loam, and there is no herbage of any sort about it. The clod contains the whole nest complete and is only 4.¼ inches deep, so that the nest is only that depth, and, therefore, very much shorter in proportion than any of our New Zealand nests. The nest (fig. 1) is slightly tortuous, but contains no enlargement, and this is different also from most of our New Zealand ones. It is lined throughout with a tough lining, and partakes more of the character of a pouch or sack than a tube, and in this approaches nearer to the Jamaica nest in our own museum. In shape it is oval, the short axis of the oval being across from the hinge area to the front or lip of the trap-door. But it is in the shape and formation of the trap-door that this nest differs most essentially from our New Zealand nests. It is thicker next the hinge than at the front, the relative thicknesses being 3/10 of an inch and 1/10. It is thickened from the under side, and not on the top or outside as in other nests, and the hinge is a continua- tion of the lining of the nest (fig. 2) extended over the upper or outside lining of the trap-door which is parallel with the surface ground. This is important, as it goes to show that there has been no enlargement of the nest from time to time. In our species, and in those described by Moggridge, the thickening and tiling of the trap-door has evidently arisen from the spider widening its hole and adding on a new and enlarged trap-door on the under surface, the hinge being always attached to the new and enlarged trap-door. But in this case no such process has been followed—in fact, there is rather evidence of the opposite, for half-an-inch in front of the mouth of the nest, the remains of part of this or of another nest is seen sticking through the soil. It is possible, however, that the original top of the nest may have been removed and that this is an entirely new one. The lid is concave on both surfaces, and the edge is bevelled so as to fit close into a corresponding countersinking in the mouth of the nest like a cork or plug. The hinge is unusually long and straight, being nine-tenths of an inch long, whilst the extreme width of the trap-door is only one and one-tenth of

an inch and forms a straight segment across one side of the oval (fig. 3). The hinge has no spring in it, but the material may have lost its elasticity, though from the shape of it I don't think it ever had any spring. The trap- door requires some force to open it from the closeness with which it fits into the mouth of the nest, but once it is opened it easily remains open. This trap-door bears very plainly the markings or punctures alluded to by Moggridge and Gosse and referred to in my former paper. On the under side of the lid in front there are four distinct sets of markings in the centre of the free edge of the lip (fig. 4). There are two sets of four holes or slits, each in the centre separated by a wider space of about a line, and then other two sets, one on each side separated from the others by a wider space of about a line, and forming a row of more minute holes for about a quarter of an inch on each side of about a dozen placed irregularly. Whatever these markings are, and the general symmetry of them is peculiar, they are certainly not air-holes as suggested by Gosse, for the holes do not penetrate through the lid. The lining of the trap-door is very tough, and the outside is covered only with red loam corresponding with the soil surrounding. No. 2 is a sod 3.½ inches deep with only the upper part of a nest and the trap-door complete. What there is of the nest is nearly straight or has only a slight bend. The lid is flat on the upper side (fig. 5), and is thicker at the hinge than at the free edge, the proportion being four-tenths of an inch and two-tenths. The thickening, as in the last case, is entirely on the under side, and the hinge is attached to the upper or outer lining of the trap-door. The free edge is markedly bevelled, being quite sharp at the edge, then concave, and then convex all round (fig. 6.) The mouth of the nest is counter-sunk for two-tenths of an inch in width and four-tenths deep, corresponding exactly to the edge of the trap-door so as to receive it accurately like a valve. The outer side is coated with plants and when shut falls into the counter-sinking about two-tenths of an inch below the surface, but this may be caused by the drying up and shrinking of the material. The under side is covered not so much with close woven cloth as with innumerable coarse threads of spider web, easily distinguishable by the naked eye, and there are no markings whatever on it. As in the last case the hinge is unusually long, and forms a straight segment across the round of the trap-door; but the great peculiarity of this nest, and one which distinguishes it from any I have ever seen, or that has ever been described, is that it is not hinged all the way across at the hinge area, but has two hinges (fig. 7), one at each extremity of the hinge area, separated by an unattached part between them. These hinges are very tough, and are respectively two-tenths and three-tenths of an inch wide. The back

part of the lid on the under side is protuberant, as shown in fig. 7, at the part that is unhinged, and it is there the lid is thickest. There is, too, an indent into the side of the lip of the nest opposite this protuberance on the lid, and into which it fits as shown in fig. 8 (which represents mouth of nest with the door off) causing the lid, when shut down, to lock, as it were, like a dove-tail, so that in order to open it again you have to insert a knife between the trap-door and the mouth of the nest. This trap-door with its hinges, locking apparatus, and counter-sinking is, I think, one of the most marvellous mechanical arrangements that I have ever come across in nature. No one can attentively examine this ingenious contrivance without being impressed with the fact that here in one of what we are accustomed to call the lowest class of animals, we have something wondrously akin to the inventive faculty in man. But this paper is one of facts and not specu- lations, and so I must forbear. As in the previous instance there is no spring in the hinges, so that the trap-door remains open when left open. Though the outside appearance of the trap-door represents the segment of an oval, still the contour of the hole inside below the counter-sinking is nearly circular as shown in fig. 8. Nos. 3 and 4.—The other two Californian nests are in the same character of ground as the preceding, and are of the same shape, and have the same description of hinge as No. 1, only they are both of smaller size. They are both thickened on the under side and bevelled on the edges like the others. No. 3 though hinged across has a protuberance slightly developed on the under side of the lid in the centre of the hinge area the same as No. 2, suggesting the idea that possibly the two hinges in that nest may have been caused by the locking effect of the protuberance as it is increased in size, but there is no evidence of unfinished or wraggled edges in No. 2 indicative of the separation having been effected by such a wearing process. On the under side of the lid of No. 4 on the free edge there are two distinct holes or claw marks exactly in front, but they do not penetrate through the lid. Both nests are lined with very tough web, are tortuous, but have no enlargement. Nests from Western Australia. These two nests (which were presented by His Excellency Governor Weld) differ entirely from the Californian. They are raised above the surface of the ground, and the lid fits on to the mouth of the nest like a cap, overlaps somewhat all round, and is thickened entirely on the outside. They are also smaller in size than the Californian. Nest No. 1 is almost circular (fig. 9: a trap-door closed; b small nest without lid); across the mouth outside it measures six-tenths of an inch, whilst the lid fitting over it measures seven-tenths; across the mouth inside

Nests of Trap-Door Spiders. To illustrate Paper by R. Gillies.

it measures four-and-a-half-tenths, and the space or ring between the inside and outside is bevelled slightly. The inside of the lid or trap-door is level, or nearly so, with the hinge, the thickening being entirely on the upper or outside of the lid. The outside edge of the lid is thin and overlaps the outside mouth of the nest like a fringe, the portion of the under side of the lid which corresponds to the bevelled or counter-sunk part of the mouth of the nest being depressed a little (fig. 11). The centre of the under side of the lid fitting on to the actual hole in the mouth of the nest protrudes a little into the nest, the whole arrangement being exactly the same as a water-tight valve covered with leather. The lid is therefore not a cork one, and does not go into the mouth of the nest at all, being large, but fits like a cap or Scotch bonnet. Nor, on the other hand, can it be said to belong to the other or wafer type of lid, as though it thins to an edge all round it thickens to the centre very symmetrically till it is at least two-tenths of an inch thick at the thickest part. The outside contour of the lid is rounded off, but at least four or five old lids can be detected, giving it a tiled appear- ance like an oyster (fig. 10). The hinge, which is large for the size of the nest (four-tenths of an inch) is attached to the outside edge of the bevelled part of the mouth of the nest (fig. 12). The inside of the lid and nest is covered with tough lining; the outside of the lid has simply the soil cemented together by threads, forming a thin covering, and remains of some mosses or lichens are still visible on it. The mouth of the nest and the lid is raised half-an-inch above the surrounding ground, and another smaller nest three-tenths of an inch wide, and also raised above the ground, is in the same sod within an inch of it. The lid, however, of the small one is gone, and the whole sod is only an inch and a-half deep, so that there is only a portion of the nest, and nothing can be said as to its former length. Nest No. 2 is of the same type as No. 1, the outside of the mouth being six-tenths across, inside four-and-a-half tenths, whilst the lid is seven- tenths. The mouth is raised above the ground, the lining being very tough and thick, and overlaps the ground a little, causing the appearance of a bevelled mouth. The lid is flat below, and overlaps the mouth slightly, forming a fringe. There is a depression all round the inside of the lid where it fits on to the mouth of the nest (fig. 13). The lid is thickened entirely on the outside, but, in contrast to the other, is as thick at the edges as elsewhere (fig. 14, front view), giving it a very odd but finished appear- ance. At the hinge area it is a little thinner than elsewhere (fig. 15, side view). The hinge is attached to the outer edge of the lining of the mouth, and is large for the size of the nest, being five-and-a-half-tenths. It differs from all others that I have seen in this: that it does not follow the round of the mouth, but is extended out at each edge beyond the circle

like the ears of a scallop shell (fig. 16, nest open). The outside of the lid has no tiling, but is formed of soil cemented together, and has remains of lichens on it (fig. 17, vertical view). The lid fits tight as a flap, and has no markings on its under side. The soil of this sod is a light brown loam; and an odd peculiarity in this nest is, that a space for the nest and for the lid has evidently been excavated (fig. 15) out of the sod or soil so as to allow of the lid opening back, which it does freely without spring, and remains open.