Chapter VIII: Part II: Trap-Door Spiders (3)

Again, Mr. F. Pollock[87] relates of the young of _Epeira aurelia_, which he observed in Madeira, that when seven weeks old they made a web the size of a penny, and that these nets have the same beautiful symmetry as those of the full-grown spider. Those of the latter are vertical, circular, made of about 250 feet of thread, having about 35 radial lines and 38 concentric circles, the outermost of which is some 20 inches in diameter. After the lapse of a day or two the web loses its adhesive property and a new one is made. In about six months the female _Epeira_ has completed her ten changes of skin, one of which takes place in the cocoon, and "at the end of eight months the spider is 2700 times as heavy as at its birth." This _Epeira_ lives, we are told, for about eighteen months.

[Footnote 87: The History and Habits of _Epeira aurelia_, in Annals and Mag of Nat. Hist. for June, 1865.]

One can scarcely contemplate the work of these architects and weavers, and especially of the trap-door makers, without being carried away into the whirlpool of discussion which has so long raged round the word _instinct_.

Do the young spiders build their first nest by instinct--that is to say, independently of all teaching or personal experience--or do they copy the nests in which they were hatched?

What is wanting, however, is not discussion, of which we have had enough, but demonstration, and demonstration is hard to come by, depending as it must upon careful and repeated experiment.

If it were practicable, and I have no reason to know that it is not, to rear spiders from the egg away from the nest, and then to cause them to build in places where they should be perfectly at home and yet cut off from all communication with their kind, we might hope to learn whether they can construct the characteristic nests of their species without ever having seen one.

Mr. Wallace[88] shows that there is some reason to doubt whether birds, which are so frequently said to build by instinct, would, under parallel circumstances, construct the nest proper to their kind; and he states that birds brought up from the egg in cages do not do so, nor do they even sing their parents' song without being taught.

[Footnote 88: Chapters on Instinct and on the Philosophy of Birds' Nests, in his Contributions to the Theory of Natural Selection.]

Of course we can scarcely compare birds and spiders together, but we should hesitate, in view of Mr. Wallace's expressed opinion as to the nest-building habits of the former, to assume that the latter are independent of teaching and personal experience. It may very possibly be so, but it has never been proved.

I have endeavoured to gather together all the published records of the nests of spiders belonging to the sub-order _Territelariæ_, with a view, if possible, to trace out the geographical range of the several types of structure. I have, however, met with but a small amount of success, and even among the limited number of tolerably complete accounts of nests which I have been able to discover, several made no mention of the spider to which the nest belongs.

Prof. Ausserer[89] has enumerated 215 species of _Territelariæ_ as having been found in the world at large, but of this large number ten only, as far as I have been able to learn, have been described in connexion with their nests, and eight of these belong to the Mediterranean region.[90] To these we may now add two more, namely, _Nemesia meridionalis_, with its branched double-door nest, and _N. Eleanora_ the builder of the unbranched double-door nest, thus making twelve in all.

[Footnote 89: In his monograph of _Territelariæ_ quoted above.]

[Footnote 90: I use this term in its widest sense, making it even include Morocco. A list of the species known to inhabit this region will be found in Appendix C.]

Three of the twelve, however, _Atypus piceus_, _A. Blackwallii_, and _Nemesia cellicola_,[91] do not appear to build true trap-doors, but only a simple silk tube without any covering at the mouth.

[Footnote 91: See Appendix A, p. 141.]

The following tabular view will show to which of the four types of trap-door nest those of the remaining nine spiders belong, and their geographical distribution:--

TRAP-DOOR SPIDERS WHICH BUILD

Nests of the cork type.

_Idiops syriacus_, Beirût.

_Cteniza fodiens (Ct. Sauvagei)_, Corsica, Pisa, Mentone.

_Ct. ædificatoria_, Tangiers.

_Ct. (Cyrtocarenum) ionicum_, Ionian Islands.

_Ct. (Cyrtocarenum) Ariana_, Naxos, Tinos.

_Nemesia cæmentaria_, South of France, Spain, Sardinia, Corsica,
Sicily, Algiers, and the var. _germanica_ from Wippach, near
Görz.

[Nests, apparently of the true cork type, have also been found in Australia, New Granada, India, and the island of Formosa, but their occupants are unknown.]

Nests of the single-door wafer type.

_Cteniza nidulans_, West Indies (and South America?)

Nests of the double-door branched type.

_Nemesia meridionalis_, Mentone, Cannes, and Sestri, near Genoa.

Nests of the double-door unbranched type.

_Nemesia Eleanora_, Mentone, and Cannes.

As far, therefore, as I know at present, the cork type of nest is the only one which is widely spread, and which is constructed by spiders of more than one species. For, while the single-door wafer, and the branched and unbranched double-door nests are each the work of one particular spider, we see that nests of the cork type are made by spiders of six distinct species, belonging to at least three genera.

It is almost certain that a much larger number of spiders of different kinds, though all probably members of the sub-order _Territelariæ_, construct nests of the cork type, for descriptions and specimens of trap-doors of this kind are brought from the most distant parts of the globe. It is true that these specimens and descriptions usually only show us the surface-door, but as far as our present knowledge goes, we are led to suppose that a door of the cork type is always associated with a simple tube, in which there is no trace of a second door or valve, so that, judging of the unknown by the known, we conclude that nests which possess the characteristic peculiarity of a true cork door are true cork nests in other respects also. Further research may possibly show that there are exceptions to this generalization, but I do not at present know of any.

I have seen Australian specimens of large trap-doors, of the cork type, measuring from one to two inches across. In some of these the doors were scarcely more than semicircular but very thick, and having their edges bevelled so as to correspond with the sloping margin of the tube;[92] in others, found at Paramatta, and described to me by Lady Parker as being tenanted by a black spider, the doors were said to be circular and much smaller, scarcely larger than a sixpence, and of the cork type.

[Footnote 92: Specimens of Australian nests may be seen in the cases at the British Museum.]

The upper portion of a nest from New Granada has been figured and described by M. Victor Audouin,[93] which closely resembles that drawn at Fig. A in Plate VII., p. 88, but the door is about a third larger.

[Footnote 93: Note sur la demeure d'une araignée maçonne de l'Amérique du Sud. Annales des Sciences Naturelles (Zoologie), tom. vii. tab. 3, p. 227-231.]

I have also been assured that nests of the cork type are found in many parts of India, and we have seen above that they are reported to be common in the island of Formosa.

Putting all this together, it will be seen that nests of this type are found all round the globe; in Formosa, India, Syria, the Grecian Archipelago, Italy, and the adjacent islands, Trieste, South France, Spain, Morocco, New Granada, and Australia; while the single-door wafer nest is only known at present in the West India islands;[94] the branched double-door nest at Mentone, Cannes, and Pegli near Genoa, and [doubtfully] near Naples and in Ischia; and the unbranched double-door type at Mentone and Cannes alone. It is quite probable that these three latter forms of nest will some day be found to have a much wider range than that assigned to them here, but I can scarcely think it likely that they will ever be shown to claim the world-wide distribution of the cork type. Supposing that these nests are eventually discovered in many widely distant localities, a very interesting question will arise as to the specific characters of the spiders which inhabit and construct them. Shall we then find, for example, that nests of the unbranched double-door type are not tenanted and fabricated by _Nemesia Eleanora_ alone, as we have hitherto found to be the case, but by many other distinct species also, each in its peculiar district?

[Footnote 94: There is a nest exhibited in the Museum collection at the Jardin des Plantes at Paris, marked "Amérique du Sud," which is perhaps of this type.]

That is to say, will the type of nest remain the same while the occupants vary, as in the cork nests?

If, on the other hand, we learn that these three types, the single-door wafer, the branched and unbranched double-door nests, are very local, we shall be led to inquire into the probable causes of this limitation.

But we must study much more closely the habits of these trap-door spiders, and the difficulties and dangers to which they are exposed, if we wish to appreciate fully the true meaning and intention of the structure of their nests, and to find the clue to the difficult question why one type should be more frequently adopted than another. Above all, we must discover what are their enemies, and how and when they are most exposed to them. M. de Walckenaer gives an entertaining account[95] of the enemies to which spiders generally are exposed, and of this the following list is an abstract.

[Footnote 95: Histoire des Insectes Aptères (Suites à Buffon), vol. i. p. 172-7.]

Many kinds of monkeys, squirrels, and several sorts of birds, as well as lizards, tortoises, frogs, and toads prey upon spiders. A species of black sheep, found in the steppes of Asiatic Russia, unearths the tarantulas (Lycosa), and eats them. ("Une espèce de brebis noire, dans les steppes de la Russie asiatique, déterre les tarentules et les mange"). In the East India Archipelago there is an entire genus of birds of the passerine order, which have been named "Arachnoptères" because the different species of which it is composed live exclusively on spiders. Besides these, the centipede (_Scolopendra_), and the following Hymenopterous insects, _Philanthes_, _Sphex_, _Pompilus_, _Pimpla Ovivora_, and _P. Arachnitor_ [which last lay their eggs in the eggs of spiders], carry on perpetual hostilities against them.

I have seen it stated that ants are among the worst enemies of spiders, driving their galleries through the silk tubes of the latter and devouring their eggs. Of this I have never seen any trace, and, on the contrary, have on four occasions found the remains of ants' bodies at the bottom of the trap-door spiders' nests.

I have but seldom detected any refuse in these nests, and this accords with what M. Erber tells us[96] of the care with which _Cteniza Ariana_, which he watched by moonlight in the island of Tinos, carried away the empty bodies of the beetles, the juices of which had been sucked out, to a distance of some feet from its hole. In October, 1872, however, I found a black layer of débris at the bottom of five nests of _Nemesia Eleanora_, and this was composed principally of the remains of insects, and among others of some rather large beetles.

[Footnote 96: A translation of these very interesting observations will be found below in Appendix B.]

As far as I am aware, M. Erber is the only naturalist who has ever placed any detailed observations on record as to the nocturnal habits of a trap-door spider in its native haunts; and we may learn from him how we should watch these creatures, if we wish to discover the manner in which they take their prey, and of what their prey consists.

He relates how he witnessed the capture, in the long low snare which _Cteniza Ariana_ spreads close to the ground, of two strong, night-flying beetles (_Pimelia_ and _Cephalostenus_), and how these were at once devoured, and their horny coats thrown away.

More observations of this kind are greatly wanted, as it is most important that we should know what are the principal sources of food upon which these spiders depend for their existence.

If we could answer the questions, what do they eat? and what do they fear? we should have advanced a long way towards resolving the larger problem as to the causes which limit particular species to certain districts.

I greatly envy those who are able to travel, and who have it in their power to investigate the habits of these creatures at several widely separated points; for there seems every probability that other new types of nest remain to be detected in warm climates, some of which may perhaps exceed those we have been here studying in beauty of workmanship and adaptation; it is at least certain that an abundant harvest of interesting facts in the life history of trap-door spiders remains yet to be gathered in.

Indeed it appears to me that we are only on the threshold of discoveries of this kind, and that the materials brought together in the preceding pages may be considered as but a small sample of what may be collected on the outermost edge of this great domain.

I shall be satisfied if I have been able in the present little work, to hold the door sufficiently ajar to permit those who love nature and her ways to catch a glimpse of the wonders and beauties of the untrodden land that lies beyond.