SUPPLEMENTTOTRAP-DOOR SPIDERS.

[115]Perhaps these heaps of corn may have been piled up at the entrance to the nest, as is sometimes the case when the workers, in their eagerness to secure as much as possible of a passing harvest, bring in the supplies too fast for their companions within the nest to be able to find room for and accommodate. When this happens the seeds lie outside the nest until fresh chambers are prepared for their reception.

The means employed by the ants to prevent the germination of the seeds contained in their granaries still remain secret, and all the experiments and investigations which I have hitherto been able to make have failed to give me the clue.

The problem to be solved is the following: Given seeds, the readiness of which to germinate has been proved, to place them in damp soil at depths varying from half an inch to twenty inches below the surface in such a manner that they shall remain there dormant, neither germinating nor decaying, for weeks and even months. These very seeds must be capable of germinating after the conclusion of the experiment.

This is what the ants do for millions of seeds, for the instances in which a few seeds appear to have sprouted within the nest in defiance of the ants, are very rare and wholly exceptional; and when after prolonged wet weather germinated seeds are seen outside the nest, it will usually be found that these have the little root cut off, and are eventually carriedback into the nest and used as food. By a fortunate chance I have been able to prove that the seeds will germinate in an undisturbed granary when the ants are prevented from obtaining access to it; and this goes to show not only that the structure and nature of the granary chamber is not sufficient of itself to prevent germination, but also that the presence of the ants is essential to secure the dormant condition of the seeds.

I discovered in two places portions of distinct nests ofAtta structorwhich had been isolated owing to the destruction of the terrace-wall behind which they lay, and there the granaries were filled up and literally choked with growing seeds, though the earth in which they lay completely enclosed and concealed them, until by chance I laid them bare! In one case I knew that the destruction of the wall had only taken place ten days before, so that the seeds had sprouted in this interval.

My experiments also tend to confirm this, and to favour the belief that the non-germination of the seeds is due to some direct influence voluntarily exercised by the ants, and not merely to the conditions found in the nest, or to acid vapours which in certain cases are given off by the ants themselves.

In order to put this latter point to the test of experiment, I confined about a hundred harvesting ants (A. structor), with their queen and several larvæ, in a glass test-tube eight inches long and one inch in diameter, closed with a cork and filled up to within about an inch of the cork with damp sandy soil, most of which was taken from the ants' nest.

I added six peas, six cress and six millet, and thenkept the tube tightly corked for nine days, only once removing the cork for a few seconds in order to sprinkle a little water on the ants, which were evidently in need of it. On the ninth day I turned out the contents of the tube and found that all the peas, millet and cress, had germinated and were growing strongly. One of the cress, however, had had its root, which lay across the gallery constructed by the ants, gnawed off; four clover seeds, which had come with the soil taken from the nest, and which had formed part of the ants' stores, had germinated also. Here the small quantity of air contained in the test-tube must certainly have become saturated with any vapour which the ants may be supposed to give off, and we cannot therefore accept this as the cause of the dormant condition of the granary seeds.

I made other experiments in which harvesting ants were imprisoned along with various seeds in small, cylindrical, closed vessels containing a little damp sand. Here the vessels were frequently rolled from side to side or shaken, during the twenty-two hours for which the experiment lasted, so as to excite the ants and make them give off such odours as they possessed, but no trace of injurious influence was produced upon the seeds, which germinated and grew normally afterwards.

At Mr. Darwin's suggestion I made a long series of experiments with formic acid, in which measured quantities, pure or diluted, were placed in a watch-glass on damp sand and surrounded by seeds, the whole being enclosed in a covered tumbler, so that the effects produced on the seeds by the vapourrising from the acid might be noted. Similar seeds were sown at the same time and in the same way, but without the acid, so as to permit of comparison. These experiments have afforded some interesting results,116but do not supply any positive data which might help us to discover the secret of the ants. They narrow, indeed, the area in which search can profitably be made, indicating as they do that the vapour of formic acid is incapable of rendering the seeds dormant after the manner of the ants, and showing, on the contrary, that its influence is always injurious to the seeds, even when present only in excessively minute quantities.

[116]I hope shortly to offer these observations, together with another series of a similar nature in which my friend Mr. J. B. Andrews has taken part, to the Linnean Society.

It appears to me now that the most promising field for experiments made with a view to clearing up this difficulty, is that afforded by the closer investigation of the phenomena of normal germination, and by a study of the conditions under which seeds remain dormant, as they are occasionally known to do, in situations which our general experience would have selected as favourable to germination.

I have good hopes, also, that when we come to know more of the habits of harvesting ants in tropical countries, and when naturalists have excavated and described their subterranean stores—a thing which has not yet been done as far as I know—we may gather fresh indications to guide us in our search.

I am puzzled to account for the fact, which I have seen stated by more than one observer in India, thatthe ants there have a habit of bringing out large quantities of grain and seed and laying them in heaps outside their nests at the commencement of the wet season. Dr. King, the director of the Royal Botanic Gardens at Calcutta, has told me that when in the Gwalior territory during the beginning of the rainy season, he saw heaps of seeds, principally those of a leguminous plant (Alyssocarpus), piled up round the entrances to the ants' nests, and that it was precisely at that time that flocks of a rock-grouse (Pterocles exustus) first made their appearance. They fed freely upon the seeds, and Dr. King found the crops of some of these birds, which he had shot, filled with them.

It is difficult to imagine why these Indian ants should turn out from their nests the very seeds which it had cost them so much labour to collect, and the more so as we find that these seeds are devoured by birds. It seems just possible, however, that the ants, remaining torpid during the rainy season, do not require the seeds, and know that, under these circumstances, if left in the nest, they would sprout, and choke up the galleries and granaries. Perhaps also they may have learned that a certain number of the ejected seeds will spring up and afford future harvests within easy reach of the nest.

All this, however, and especially the suggestion as to the dormant condition of the ants during the rainy season, might easily be proved or disproved by direct observation; and at present we have nothing but mere speculation to go upon.

It is curious to find that the native population in a certain part of India pay a kind of tribute to theants, for Dr. King informs me that the Hindoos in Rajputana, a province in which the old traditions and superstitions retain especial hold, have a custom of scattering dry rice and sugar for the ants, and thus apparently recognise both their love of sweet things and their habit of collecting seeds. It may be that this custom is now little more than a meaningless rite; but in the past it probably had its origin, either in a wish to propitiate the good will and avert the destructive attacks of creatures which are the scourge and dread of entire districts, or in a sentiment of combined fear and admiration—fear of the power, and admiration of the energy, forethought, perseverance, and sense of duty to the community displayed by these marvellous insects.

That the latter feeling may have had some share in prompting this act is suggested by another custom which is stated117to prevail in Arabia, in accordance with which an ant is placed in the hand of a newly-born child, in order that its virtues may pass into and possess the infant.

[117]Freytag, paragraph under the Arabic word for Ant, in hisLexicon Arabico-Latinum, vol. iv. p. 339, where he quotes from a local dictionary.

Among the many curious and obscure features in the economy of ants, one of the most interesting is the occasional presence in their nests of different creatures which live among and often in harmony with them, the nature of the relations between host and guest being for the most part quite unknown.

When examining the contents of some granaries from an extensive nest ofAtta structorat Mentone last spring (1874), I found large numbers of aminute, shining-brown beetle moving about among the seeds. These little creatures were themselves not unlike some very small seeds, and were of an elliptic form, measuring a trifle less than one line in length. They proved to belong to the scarce and very restricted genusColuocera.118This species, named by KraatzC. attæ, on account of its inhabiting the nests of ants belonging to the genusAtta, has been found in Greece.

[118]I am indebted to Mr. F. Smith of the British Museum for the name of this beetle and for the following reference to its description; Kraatz inBerliner Entomologische Zeitschriftfor 1858-9, p. 140.

Mr. Bates,119in his most interesting account of his travels on the Amazons, remarks upon the singular fact, of which the above instance is an example: "that some of the most anomalous forms of Coleopterous insects are those which live solely in the nests of ants," and he then goes on to allude to the strange snakeAmphisbæna, a native of that region, which also lives in the nests of the Sauba ants (Œcodoma cephalotes), observing how curious it is that an abnormal form of snakes should be found in the society of these insects. He is of opinion, however, that theAmphisbænais not an inoffensive guest, but lives upon the ants whose nest it selects for its home.

[119]Naturalist on the Amazons, p. 61-2 (Ed. 2, 1864).

Another remarkable inhabitant of ants' nests is a minute cricket, of which I found a single example in the midst of a colony of black ants at Mentone in February, 1874. This miniature cricket is scarcely as large as a grain of wheat, the body, excluding the antennæ and other appendages, measuring only two lines in length. It has been described by Dr. PaoloSavi120under the name ofGryllus myrmecophilus. He detected it in the nests of several species of ants in Tuscany, where it lived on the best terms with its hosts, playing round their nests in warm, and retiring into them in stormy weather, while allowing the ants to carry it from place to place during their migrations.

[120]Dr. P. Savi,Osservazione sopra la Blatta acervorum di PanzerinBibliotheco Italiana, tom. xv. p. 217.

Gryllus myrmecophilushas also been observed in nests of the turf ant (Tetramorium cæspitum) near Paris.121

[121]Bulletin Soc. Entom. de France(1872), p. li.

At Mentone I have never found more than this one specimen, and the ants among which it was domiciliated were of a species new to me (Camponotus(Formica)lateralis, Oliv.). This colony of ants was composed of many winged males and females, as well as workers, the last-named measuring from two and a half to three lines in length, and black in colour. In other colonies I have found the workers black, with red head and thorax.

Another ant, not enumerated in my list inAnts and Spiders, isCamponotus(Formica)sylvatica, which I detected in March last under stones on Cap Martin, near Mentone. When disturbed, this ant runs along with its abdomen raised vertically in the air, much as the devil's coachhorse (Staphylinus) does. The same curious habit of erecting the abdomen is found in another ant, not uncommon in decaying wood in the South,Crematogaster scutellaris; and probably all three insects adopt this threatening attitude, which is that of the scorpion preparing to strike and sting, inorder to intimidate their enemies, thoughCrematogasteris the only one which really possesses a sting.

Camponotus sylvaticahas the same long legs and slender body asFormica cursor, and is of about the same size; the workers, which are of a dark brown colour, measuring about 31/2lines in length.

Perhaps it may be well, in concluding these remarks on Harvesting Ants, to call attention to the principal questions which still await solution. The first is one which any observer who travels in Central Europe during the summer may help to solve.

1. Doanyants collect and store seed in Switzerland, Germany, North France, England, or indeed in any of the colder parts of the world?

2. What are the habits ofAtta structorandA. barbarawhen living, as they are known to do, in Switzerland, Germany, and Northern France?

3. How do the ants contrive to preserve the seeds in their granaries free from germination and decay?

4. How are the seed-stores of tropical ants disposed below ground, and of what do they consist?

5. Do harvesting ants exist in the southern states of North America, in Australia, New Zealand, or at the Cape?

There would doubtless be a just feeling of pride and satisfaction in the heart of a naturalist who could say that he had made himself thoroughly acquainted with all the species of a particular group of animals, had learned their most secret habits, and mastered their several relations to the objects, animate and inanimate, which surrounded them. But perhaps a still keener pleasure is enjoyed by one who carries about with him some problem of the kind but partially solved, and who, holding in his hand the clue which shall guide him onwards, sees in each new place that he visits fresh opportunities of discovery. The latter is certainly the condition of those who take an interest in searching out the habits and characters of trap-door spiders; for this subject, far from being exhausted, expands under the light of recently acquired facts, and invites research in many parts of Europe, north as well as south.

We have only to compare the number of types of trap-door nest which were known before the publication ofAnts and Spiders, with those at present recorded,to see how fruitful this field of inquiry has already proved.

Before this little work was published, only one type of trap-door nest was known in Europe: two new types were described in its pages, and I have now the pleasure of being able to bring three more hitherto unknown European types before the notice of my readers, thus raising the number to six in all. I do not include in these six types the very curious, and still imperfectly-known nest ofAtypus;122a spider which is a true representative of the trap-door group as far as its structural characters are concerned, but which, although it excavates a silk-lined burrow in the earth, does not appear to construct any kind of door at the mouth of its tube.

[122]SeeAnts and Spiders, page 78.Atypusbelongs to the sub-familyAtypinæ, a division which does not include any of theNemesiasorCtenizas, and of which indeedAtypusis the only European representative.

Much uncertainty still hangs over the habits of this spider, as the facts hitherto recorded, though perfectly authentic, are difficult to piece together into a satisfactory whole. One thing, however, is clear, and that is, that the nests and habits of the spiders of the genusAtypus(of which, as Mr. Pickard-Cambridge, informs me, two if not three distinct species inhabit England) merit attentive study, and would most certainly repay it. Hastings, Portland, the coast of Dorsetshire, and the neighbourhood of London and Exeter, are the habitats hitherto cited for this spider, but I cannot doubt its existence in many sheltered localities on the south coast of England.

The most recent contribution to our knowledge ofthis genus is contained in a paper by M. Eugène Simon,123who describes three species (two of which are new), as inhabiting France, and it remains to be ascertained whether our BritishAtypiagree in their characters with any of these.

[123]Note sur les Espèces françaises du genreAtypus, Latr. in Ann. Soc. Entomologique de France, 5eser. tom. iii. (1873), p. 109.

He describes (p. 113-4) the nest and mode of life ofAtypus piceus, Sulzer (=A. Sulzeri, Latr.),124the commonest of the three species, as follows:—"They (the spiders) seek dry and somewhat sandy slopes, sometimes also woods, chiefly plantations of evergreens; their retreat is always concealed either by stones, or in moss which one must remove carefully and in large masses (plâques) in order to detect them."

[124]Thus named by M. Simon.

"This Atypus excavates an oblique hole of 15 to 20 centimetres deep, and of the size of its body; it lines it with a rather narrow silken tube of a very close texture, the upper part of which, exceeding the subterranean portion in length, lies horizontally on the surface of the ground, and ends in an open tapering point. Near its lower extremity the tube is suddenly contracted, and then dilates into the form of a fairly spacious apartment, in which the spider lives; the cocoon enclosing the eggs is suspended by a few threads at the contraction. I have frequently surprisedAtypusin the act of holding earth-worms in their falces, and I think that these Annelids constitute the larger part of their food; indeed, if one examines the lower portion of the silk chamber, one may remark a part where the tissue is thinner and more transparent. I have not been able to detect an opening, but it is probable that theAtypuscan easily part the not very compact threads, and thus obtain for itself an easy prey, and dispense with the necessity of ascending to the surface of the ground. When taken out of its tube,Atypusdoes not even attempt to escape; it is therefore plain that it is not organized for the pursuit of an active prey; and, on the other hand, the upper extremity of the tube is ill-adapted for an ambuscade, being almost closed, and without support. This small opening would seem to be solely intended for the entrance and exit of the male (a very much smaller creature than the female) during the breeding season, which occurs in the month of October."

Plate XIII

M. Simon says that this species ofAtypusis common in all the centre, east and west of France, and that he has detected it in great abundance in the neighbourhood of Troyes, in Champagne, in the month of October, when the male was inhabiting the same tube with the female.125I am greatly indebted to M. Simon for having given me the specimen of a silk tube taken entire from a nest found in this locality, which I have figured inPlate XIII, fig. A. It will be seen that the tube has collapsed, but one may still trace the enlargement near the base which forms the chamber, the elbow where it is bent at the surfaceof the ground, the moss, scales, and fibres of plants which are woven into, and serve to conceal the aërial portion, and its termination in a twisted and apparently-closed mouth.

[125]M. Simon has discovered another species ofAtypusat Digne in the Basses Alpes which constructs a similar nest to that described above. This species was detected for the first time by M. Simon and described by him under the name ofAtypus bleodonticus.

Indeed, I believe that, in this specimen, the upper extremity of the tube is really closed, for, when I succeeded in inflating this aërial portion, the lips did not part, but remained drawn together.

It seems very extraordinary that the mouth of the tube should be thus closed, so that the female spider becomes a prisoner, self-immured, and I can only suppose that this is a temporary condition, limited perhaps to the period during which she receives the visits of the male.

At the very base of the tube I found a mass of earth, roots and vegetable fibres, and in this I hoped to have detected thedébrisof insects or other food, such as I sometimes find at the bottom of and below the tubes of the trap-door nests in the South, but of this there was no trace.

It is difficult to me to imagine how the spider could contrive to live by the capture of worms, after the fashion suggested by M. Simon; for who does not know the speed with which, on the slightest alarm, worms draw back into their holes and escape pursuit, and the muscular power which they exert in resisting any attempts to drag them out of the earth?

M. Simon's account of the closed tube and capture of worms by this spider corresponds, however, with that given by Mr. Joshua Brown, the first discoverer ofAtypusin England.

This gentleman communicated his discovery to Mr.Edward Newman126in 1856, since which time (with the exception of M. Simon's paper quoted above) little or nothing seems to have been done to clear up the points which remain doubtful in the history of these singular creatures.

[126]Note onAtypus Sulzeriof Latreille, by Mr. Edward Newman, read before the Linnean Society; a report of this communication is given inThe Zoologist, vol. xiv. (1856), p. 5021.

Several nests ofAtypuswere discovered by Mr. Joshua Brown in the neighbourhood of Hastings, when traversing a lane bounded on either side by high and steep sand-banks, partially covered with grass and bushes.

His attention was at first arrested by the sight of "something hanging down which looked like the cocoon of some moth;" but, on closer examination, the silk case proved to be empty, and was continued as a tube into the ground to a depth of 9 inches, where he came upon the spider lying at the bottom. Further research revealed the existence of a number of these nests in the same locality, but the length of the different tubes varied much; they were usually about 9 inches long, but some were much longer, often baffling his attempts to follow them; the longest which he was able to secure entire measured 11 inches. All the nests were, however, alike in having a tubular silk lining, about3/4of an inch in diameter, a part of which protruded from the ground for about 2 inches, and was pendent, inflated, and covered with particles of sand, assimilating it to the surrounding surface; it was closed at the upper extremity, leaving no exit to the open air.

Mr. Brown took home some of these tubes in acollapsed state with the spider at the bottom. In one case, on opening the box in which the nest was placed, he perceived a movement throughout the tube, as if it were being inflated; this however soon subsided, but the following morning he was surprised to see that the whole tube was inflated, especially at the end which had lain exposed on the bank. He failed to find any aperture by which the spider could enter or leave her nest, and his captives, though passing backwards and forwards in their tubes, never came out at either end. He never saw flies or any fragments of insects in the nests; but, on drawing out one of the tubes, he observed a worm at the lower end, partially within it, partially outside, and he perceived that the spider had evidently been eating a considerable portion of its anterior extremity.

It will readily be seen that there are some discrepancies between the different accounts which have been given of the nests ofAtypusfound in England and France,127and I think it quite probable that some at least of the nests described may really differ, and be the work of distinct species belonging to this genus. Mr. Brown describes his nests as having by far the greater part of their length under ground, while in those observed by M. Simon, as shown in my figure,Plate XIIIfig. A, the exposed portion of the tube equalled or exceeded the subterranean.

[127]A subject already alluded to inAnts and Spiders, at p. 78.

An imperfect specimen at the British Museum, from some English station (exact habitat not given), appears to have the proportions described by Mr. Brown; the length of the aërial portion of the tubebeing less than one-fourth of that of the subterranean; the upper end of the tube is however open, but I am doubtful whether this was originally so or not, for the silk is torn at this point, and the opening may be a rent caused by rough handling.

After a comparison of the above description, it appears to me that the following are the principal points which remain to be cleared up:

1. What is the precise structure of the nests of Atypus, and are they always uniform in character at all seasons of the year?

2. What is the use of the exposed aërial portion of the tube?

3. Do the two British species make similar nests?

4. What food, besides worms, does the female live upon, and how does she obtain it?

5. Does she ever leave the nest?

6. What becomes of these spiders and their nests in the winter, and how long do they live?

7. When do the young leave the nest; and do they, like their relatives in the South, construct nests like those of their parents in miniature?

I would commend all these points to any lover of Nature who may seek the southern coasts of England during the autumn and winter months, and I think it more than likely that a careful search in the sandy banks near St. Leonards, the slopes under the fir-woods of Bournemouth, and the deep lanes in the neighbourhood of Torquay, would be rewarded with success.

If the breeding season in England only commences in October, as appears to be the case in France, it would seem most probable that the spiders survivethe winter. Very possibly these spiders and their nests might be transplanted and placed for observation in a garden; and if room were granted them in a greenhouse or Wardian case, or even in a large flower-pot in a living-room, it is not unlikely that the warmer temperature might waken them up to renewed activity.

It seems clear thatAtypushas to fear the insidious attacks of enemies; for not only is the external portion of the tube closed or almost closed at certain seasons, but it is covered outside with such materials as may serve to make it resemble the surrounding surface of the ground. Thus Mr. Brown's nests, lying on a sandy bank, were covered with particles of sand, while my specimen from Troyes has moss and fibres of plants woven into its upper extremity.

Indeed, all the European representatives of the suborderTerritelariæwhich I have myself met with, conceal their nests with great care and skill. There appear to be others, however, which either make no nests at all but hide under stones, or only construct a simple silk tube, open at the mouth, and without any special contrivance for its dissimulation. Further observation of the habits and dwellings of these apparently unworthy members of the trap-door group is much to be desired.

Mr. Bates,128in his work on the Amazons, describesMygale (Theraphosa) Blondii, a large and powerful spider of that region, as burrowing into the earth and "forming a broad slanting gallery about three feet long, the sides of which he lines beautifully withsilk." This spider "is nocturnal in his habits," and maybe seen "just before sunset keeping watch within the mouth of his tunnel, disappearing suddenly when he hears a heavy foot-tread near his hiding place."

[128]Bates, H. W.,Naturalist on the Amazons, Ed. 2. (1864).

This nest would therefore appear to have an open tube undefended by any door; but in this case the great size of the spider and the depth of the burrow, which is more than twice as long as that of the average European nests, may help to explain this apparent want of precaution.

But, if we wish to learn with what different materials and by what varied means the same end of self-preservation can be attained, we have only to cast a glance at the sketch of a portion of a nest at fig. B,Plate XIII, p. 183, where it will be seen that the entrance to the nest, far from being concealed or obscured in any way, is rendered a most striking object, and one which appears devised for the very purpose of attracting attention. The nest to which I refer is the work ofCyrtauchenius elongatus, from Morocco, and consists, according to the account given me by its discoverer, M. Simon, of a deep cylindrical burrow in the soil, the silk lining of which is prolonged upwards for about three inches above the surface of the ground, and enlarged into a funnel shape, so that it becomes from two to three inches across at the orifice. This aërial portion being snow-white, at once attracts the eye even from a considerable distance, and the nests rising up amid the sparse grasses and other small plants which serve to support but not to conceal them, present the appearance of scattered white fungi.

This is therefore quite a new type among the nests constructed by trap-door spiders, new in form andprobably in function also, and I would propose to distinguish it provisionally as thefunnel type.

Now the femaleCyrtaucheniusis, like its near relatives theNemesias, a sluggish and rather helpless creature, and shows no apparent physical superiority which might countenance its dispensing with the methods of concealment which form the characteristic habit of the group.

How then does this spider manage to escape its many enemies, especially the insidious attacks of the insects of theSphexandIchneumonfamilies, which certainly abound in Morocco?

Mr. Wallace, to whom I put the question, suggested that this species may perhaps be chiefly nocturnal in its habits, and that, if this is the case, the bright white and flower-like tube of the nest may possibly serve to attract night flying insects, which would thus become its prey.

In any case, whether we can discover them or not, some curious points of difference must exist between this spider and its allies, which secure to it a comparative immunity.

It appears to me that there are few questions which can be of greater interest to the naturalist than those which have to do with the conditions determining the existence of a given species in a given place.

Of the questions, Who are your relatives? Where do they live? and How are you able to live here? surely the last is not the least important.

And, if we wish to try to answer this question, we must do all in our power to find out how the habits and conditions of life of the creature in question,differ from those of its competitors; for we may be quite certain that it does not exist where we see it by grace and favour, but by merit; if it is neither stronger, cleverer nor more numerous than its neighbours, we may be sure that it has found some means of living which does not interfere fatally with their requirements. Hence the endless diversity of function and habits in all living creatures, which forms such a prolific and marvellous subject for our study and contemplation.

I am indebted to M. Simon for permission to publish the details given above onCyrtauchenius elongatus, and also for having given me such directions as enabled me to make the sketch from which the drawing atPlate XIII, fig. B, was copied.

I must however state that this illustration is not taken from an actual specimen, but is prepared solely from his description; so that it cannot pretend to complete accuracy of detail. M. Simon assured me nevertheless that it conveyed the general appearance of this remarkable nest with sufficient fidelity, and I have been induced to reproduce it here in the hope that it may serve to make my meaning plainer, and to suggest the kind of object which one should look for, if an opportunity offered.

Another species of the same genus,Cyrtauchenius Doleschallii, is known to inhabit Sicily, but the nest is undescribed. M. Lucas has described two species,129belonging to the closely-allied genusCyrtocephalus, both of which appear to construct nests somewhat similar in form to that discovered by M. Simon.Whether these nests are equally showy we cannot tell, as the account is brief and few details are given; but one, that ofCyrtocephalus terricola, appears to differ in having threads stretched from the opening of its funnel, which serve to ensnare insects and to give notice of these captures.

[129]Cyrtocephalus Walckenaëriandterricola, Lucas (H.),Animaux articulés de l'Algérie(Paris, 1847-9), vol. i. p. 94-5.

The great trap-door group therefore comprises spiders which differ widely in respect of their dwelling places. Some construct no nest at all or only an irregular web, and live under stones; others, likeTheraphosa Blondii, make a simple cylindrical tunnel, or, like those just described, a tube having a prolonged, uncovered, funnel-shaped mouth: others again, belonging to the genusAtypus, form the curious and as yet imperfectly-understood nests with a silken tubular lining, part of which hangs down outside; while on the highest rung of the architectural ladder, stand the builders of the veritable trap-door nests.

It seems quite possible that, when we know more of the structures made byTerritelariægenerally in various parts of the world, we shall find that nests of various degrees of complexity and perfection of structure exist, bridging over the gulf between the barbarous dwellers under stones and the highly civilized inhabitants of the branched wafer and cork nests.

Indeed, thanks to recent discoveries, I am already able to do something of this kind for one small group of spiders, namely, for that of the EuropeanNemesiashaving nests with wafer doors.

Plate XIV.

I hope to make this plain by reference to the diagrams onPlate XIV, where the figures C, D, E, F, and G represent on a reduced scale five types of wafer nest constructed by as many distinct spiders, and where a gradation may readily be traced between the simplest type at C and the most complicated at G; but we shall speak more fully of this matter by-and-by.

In these diagrams I have placed that representing the nest ofAtypuson the extreme left (A);130next to this stands that of a nest of the cork type (B), a type which must be carefully distinguished from all the rest. It must not be supposed that the solid cork door (so called from its resemblance to a short cork closing the neck of a bottle), is nothing more than a thicker edition of the wafer door; it is not so, but, on the contrary, possesses a very characteristic structure of its own, being composed of many layers of silk, each furnished with a sloping rim of earth, while the wafer door consists of but a single layer of silk.

[130]These types may be briefly enumerated as follows:A,nest ofAtypus.B,cork nest, and B, 1, layers of silk and earth forming the door of the cork nest.C,single-door, unbranched wafer nest.D,single door, branched wafer nest.E,double-door, unbranched wafer nest, and E, 1, lower door of the same.F,the Hyères double-door branched wafer nest, and F, 1, lower door of the same.G,double-door branched cavity wafer nest, as seen in the oldest and largest specimens, and G, 1, the same in the younger specimens. G, 2, the lower door of this nest, being of the same form in young and old nests.

[130]These types may be briefly enumerated as follows:

I have represented at B 1 the 14 layers of silk and earth which went to make a single cork door examined by me. It will be seen that the outermost of these layers is the largest, and the innermost the smallest, and I have already (Ants and Spiders, p. 150) shown reason for believing that the latter constitutedthe first door the spider ever made, and that the consecutive layers mark successive stages in the enlargement of the nest.

There is therefore a broad distinction as to construction between cork nests and wafer nests; moreover, while the former are, as far as we know at present, all of one type, and only differ in size or proportion, the latter appear under five distinct types.

Thus, every known cork nest, whether found in Europe, America, or the Antipodes, has the same solid door and simple tube; while of the wafer nests, some have branched and others simple tubes, and some again possess a lower door in addition to the upper or surface door.

In the following pages I intend to treat of the trap-door spiders and their nests in the same order in which the latter are placed in the diagram, commencing with those of the cork type B, and then dealing successively with the several wafer nests from C to G. We have already spoken of A, the nest ofAtypus piceus, and seen that our present knowledge of this nest, of the habits of its occupant and of those of its relations, is still far from complete.

The cork type is, as my readers will perhaps remember, the great cosmopolitan type which ranges round the world, and which, curious to say, is built by many different spiders belonging to distinct genera.

The idea of planning this very perfect bit of mechanism appears to be the common inheritance of these several spiders, separated though they are by wide intervals of geographical space as well as to structural divergence.

At Mentone two distinct spiders construct nests of the cork type, one of these being aNemesiaand the other aCteniza. They are as unlike each other as they well can be, and it seems remarkably strange that their nest-building instinct should be so similar. The nest of theCtenizais indeed shallower than that of theNemesia, and a practised eye can usually trace a difference between the slightly less angular lower surface and more semi-circular outline of the door of the former, and the more abruptly bevelled and more circular door of the latter.

These spiders and their nests have been already described and figured inAnts and Spidersunder the names ofCt. fodiensandNemesia cæmentaria. Recent discoveries have however shown that these spiders possess distinctive characters of their own, and, though closely allied to the species indicated, should be separated from them.

Last spring when pulling down an old terrace-wall (by permission) I had the good fortune to discover the very remarkable maleCtenizadrawn at fig. A,Pl. XX, p. 254. I found no trace of a nest or web of any kind, and the spider was merely hiding between the stones.

There appears to be scarcely any doubt that this is the male of the female MentoneseCtenizawhich has, up to this time, been calledCt. fodiens. A comparison with typical specimens of the trueCt. fodiensfrom Corsica, has however shown that the two are certainly distinct, and Mr. Pickard-Cambridge131nowdescribes the Mentonese form under the name ofCt. Moggridgii.132

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