Chapter III: Part I: Harvesting Ants (1)

It was in May, 1869, that Mr. Bentham in his presidential address to the Linnean Society called attention to the want of reliable information as to the existence of such subterranean accumulations of seeds as are popularly supposed to account for the sudden appearance on railway cuttings, gravel from deep pits, and the like, of crops of weeds hitherto unknown in a district.

He suggested that it might repay the trouble if some accurate observers were to take this in hand, and investigate the matter both by examining samples of undisturbed soil taken from various depths,--when, if any seeds of moderate size were present and undecomposed, it would be tolerably easy to distinguish them,--and also by ascertaining what means of transport exist by which seeds may be scattered over exposed surfaces, and thus explain the difficulty without having recourse to hypothetical supplies of sound though long-buried seeds.[1]

[Footnote 1: M. Kerner of Innspruck has lately adduced some facts bearing on the question of the transport of seeds by the wind, having examined the collections of animal and vegetable substances found on the icy surfaces of glaciers and the plants growing on moraines. Judging from the facts thus obtained, he attributes but a small influence to this agency, as the specimens discovered belonged to the fauna and flora of the immediate vicinity, and not one of these specimens must needs have come from a distance. See abstract of his paper in Gardener's Chronicle, Feb. 3, 1872, p. 143, and in 'Nature' for June 27, 1872, p. 164.]

As I listened, the question occurred to me whether the ants, which I had observed carrying seeds to their nests at Mentone, might not be unconscious agents on a small scale, both in the distribution and the subterranean storing of seeds. When at a later time I made this suggestion to some of our leading naturalists, I learned with considerable surprise that the unanimous opinion of our highest modern authorities on the subject is opposed to the belief that European ants ever do systematically collect and make provision of seeds, and that the instances of such occurrences in tropical climates remain as isolated though undoubted facts which it is difficult to explain.

I was not then aware that towards the middle of last century the ancient belief, dating from the time of Solomon, that ants habitually show forethought and husbandry in the collection of supplies of seeds and grain had begun to be called in question, and that our most able observers, such as Huber, Gould, Kirby and Spence, and at the present day Mr. Frederick Smith, had by close scrutiny of the habits of these creatures proved that, wherever personal investigation had enabled them to put the matter to proof, no trace of harvesting was found.[2]

[Footnote 2: I have myself on many occasions thrown seeds in the track of the common English ants, and my experience was, up to the past summer (1872), similar to that of the above-named naturalists, but I have lately, by the merest chance, become acquainted with a curious exception to this rule. It happened as follows. I was gathering some fresh capsules of the common sweet violet in a garden at Richmond, near London, and in pouring the seeds out of my hand into the paper bag made to receive them, a few were spilled on the ground. In a short time afterwards I was greatly surprised to see some of these spilled seeds in motion, being carried by the common black ant (_Formica nigra_) into its nest. On seeing this I hastened to get some more fresh violet seeds, and also a quantity of seeds taken from ant's granaries at Mentone, and scattered these where the other seeds had lain. After watching for half an hour a few of the violet seeds were carried in, but not one of the granary seeds was removed, though these were examined with some curiosity. I repeated this experiment twice afterwards on a distinct colony of ants of the same kind and obtained exactly the same result. I opened the nest of the former colony on the day after they had carried in the seeds, but failed to find these or any stores of other seeds.

I am inclined to think that the ants took these seeds believing them to be larvæ of other ants which they might eat; for fresh seeds of violet are not very unlike the larvæ of certain ants, as, for example, those of _Atta barbara_, figured at Plate I., Fig. E., p. 21, the semi-transparent membranous appendage partly concealing the seed and giving it a fleshy appearance.

I think this the more likely because on two occasions the seeds which had been carried into the nest were subsequently thrown out by the ants, which had I believe discovered their mistake.]

However, just as the ancient writers, judging from their own experience and from the reports of others, had erred in attributing to ants in general the habit of seed-storing possessed by certain species commonly found in the south, so have modern naturalists fallen into the mistake of denying it to any of the European species.

The older authors who lived in Greece and Italy, and the mediæval authors who drew their information in great measure from the former, being familiar with the fact that some ants habitually collect large supplies of seed, went so far as to assert, or to imply, that all European ants do so; the authors of the present day, on the other hand, generalizing too freely from their experience of ants found near their northern homes, maintained and maintain the very reverse.

So long as Europe was taught natural history by southern writers the belief prevailed; but no sooner did the tide begin to turn, and the current of information to flow from north to south, than the story became discredited.

It is interesting now to recall a few of the allusions to the harvesting ants made by ancient authors, some of which contain tolerably accurate accounts of what was to them a familiar sight or a universally accepted fact.

The passages in Proverbs[3] are the following: "Go to the ant, thou sluggard: consider her ways and be wise; which, having no guide, overseer, or ruler, provideth her meat in the summer, and gathereth her food in the harvest." "The ants are a people not strong, yet they prepare their meat in the summer." Hesiod[4] speaks of the time

"When the provident one (the ant) harvests the grain."
ὅτἐ τ ιδρις σωρὀυ ἁμαται.

[Footnote 3: vi. 6-8 and xxx. 25.]

[Footnote 4: Works and Days, 776.]

Horace[5] also alludes to the foresight of the ant, who is "haud ignara ac non incauta futuri." Virgil[6] compares the Trojans hastening their departure to harvesting ants, and the passage has been thus rendered by Dryden:--

"The beach is covered o'er
With Trojan bands, that blacken all the shore:
On every side are seen, descending down,
Thick swarms of soldiers, loaden from the town,
Thus, in battalia, march embodied ants,
Fearful of winter, and of future wants,
T' invade the corn, and to their cells convey
The plundered forage of their yellow prey.
The sable troops, along the narrow tracks,
Scarce bear the weighty burden on their backs;
Some set their shoulders to the ponderous grain;
Some guard the spoil; some lash the lagging train;
All ply their several tasks, and equal toil sustain."

[Footnote 5: Satires I. i. 33.]

[Footnote 6: Æneid, Bk. iv. l. 402.

"Ac velut ingentem formicæ farris acervum
Quum populant, hiemis memores, tectoque reponunt:
It nigrum campis agmen, prædamque per herbas
Convectant calle angusto; pars grandia trudunt
Obnixæ frumenta humeris; pars agmina cogunt,
Castigantque moras; opere omnis semita fervet."
]

Indeed, it would seem that among the people inhabiting the shores of the Mediterranean it was almost as common to say "as provident as an ant" as it is with us to say "as busy as a bee." Plautus[7] introduces a slave who, when attempting to account for the rapid disappearance of a sum of money of which he had charge, says,

"Confit cito
Quam si tu objicias formicis papaverem."

"It vanished in a twinkling,
Just like poppy seed thrown to the ants."

[Footnote 7: Trinummus, Act ii. sc. 4, l. 7.]

Any one who has seen the eagerness with which certain southern ants seize upon seeds thrown in their path will appreciate the correctness of this simile.

Claudius Ælianus, who lived in the time of Hadrian, gives a detailed account of the habits which he attributes to ants,[8] from which the following is a translation: "In summer time, after harvest, while the ears are being threshed the ants pry about in troops around the threshing floors, leaving their homes, and going singly, in pairs, or sometimes three together. They then select grains of wheat or barley, and go straight home by the way they came. Some go to collect, others to carry away the burden, and they avoid the way for one another with great politeness and consideration, especially the unburdened for the weight carriers. Now these excellent creatures, when they have returned home, and stored their granaries with wheat and barley, bore through each grain of seed in the middle; that which falls off in the process becomes a meal for the ants, and the remainder is unfertile. This these worthy housekeepers do, lest when the rains come the seeds should sprout, as they would do if left entire, and thus the ants should come to want. So we see that the ants have good share in the gifts of nature, in this respect as well as others." Further on[9] he gives a very interesting account of their mode of collecting and preparing the grain, many details of which I can myself substantiate from personal observation, though I have never seen ants actually at work upon the ears of corn. "But when the ants start a foraging, they follow the biggest, who take the lead as generals. And when they come to the crops, the younger ones stand under the stalk, but the leaders ascending gnaw through the culms, as they are called [ὀυραγοὑς, 'the stalk ends on which the ears grow' (Lid. and Scott, Gr. Lex.)], probably meaning that they detach the separate spikelets of which the ears are composed], of the ears [καρπἱμων], which they throw to the people below. These busy themselves with cutting away the chaff and peeling off the envelopes which contain and cover the grain. So the ants, though they need no threshing time, nor men to winnow for them, nor an artificial draught of wind to separate corn and chaff, yet have the food of men who both plough and sow for it." Ælian appears also to have heard reports of the habits of ants in tropical countries, for he says,[10] "Certainly the Indian ant is also a wise creature.... They leave one opening at the top (of the nest), by which they have their exits and entrances, when they come bearing the seeds which they collect." I have never myself found seeds bored through the centre in the way recorded above, but it is possible that different species of ants may treat the seeds in other ways than those observed by me; or, on the other hand, Ælian may have mistaken the gnawing off the radicle of the seed, a process which I shall describe from personal observation below, and imagined that the seed itself was pierced.

[Footnote 8: Ælian, De Naturâ Animalium, ii. 25.]

[Footnote 9: Ælian, De Nat. Anim., lib. vi. chap. xliii.]

[Footnote 10: Id. lib. xvi. 15.]

Aldrovandus, writing in the sixteenth century, speaks[11] of the ants as storing seed and of their gnawing, "illud principium seu acumen grani, è quo germen emitti à tritico solet"--that is to say, the radicle. But it is not clear whether Aldrovandus treats of what he has himself seen or refers to the account given by a certain Bishop, Simon Mariolus, who, he says "in his most pleasant and learned work, introduces a philosopher as taking his walks abroad and examining an ant's nest with its seed store," &c.

[Footnote 11: Aldrovandus, De Insectis, lib. v. (de Formicis).]

The lively fable of the ant and the grasshopper, as related by La Fontaine, has done much towards familiarizing and keeping alive in the minds of many of us the idea that ants habitually provide stores against the winter; but we must not infer from this narration that the witty French author had ever cared to examine for himself whether the fable, which he borrowed from Æsop, had its foundation in fact or not. The following translation from, the Greek original[12] bears in a much higher degree the impress of personal and accurate observation.

[Footnote 12: For this translation and all the foregoing extracts from ancient and mediæval authors I have to thank my brother, M. W. Moggridge.]

Μὑρμηκες καἰ Τἑττιξ: The Ants and the Grasshopper. Once in winter time the ants were sunning their seed-store which had been soaked by the rains. A grasshopper saw them at this, and being famished and ready to perish, he ran up and begged for a bit. To the ant's question, "What were you doing in summer, idling, that you have to beg now?" he answered, "I lived for pleasure then, piping and pleasing travellers." "O, ho!" said they, with a grin, "dance in winter, if you pipe in summer. Store seed for the future when you can, and never mind playing and pleasing travellers."[13] It would be easy to multiply instances in which the older authors allude to this habit, but enough have been given to afford a sample of what may easily be found repeated elsewhere, and I will now quote a few instances which illustrate the more modern belief, utterly opposed to that so long maintained by the ancients.

[Footnote 13: Æsopicæ Fabulæ (Tauchnitz edition), p. 92.]

Messrs. Kirby and Spence[14] discuss the matter in the following terms:--"When we find the writers of all nations and ages unite in affirming that, having deprived it of the power of vegetating, ants store up grain in their nests, we feel disposed to give larger credit to their assertions. Writers in general have taken ... (this) ... for granted. But when observers of nature began to examine the manners and economy of these creatures more narrowly, it was found, at least with respect to the European species of ants, that no such hoards of grain were made by them; and, in fact, that they had no magazines in their nests in which provisions of any kinds were stored up."

[Footnote 14: Entomology, ed. 7 (1856), p. 313.]

They then proceed to explain how easily the white pupæ, which the ants carry about in their jaws, may have been mistaken for grains of wheat, and to inform us that the accurate observations of Mr. Gould, published in 1747, were among the first which led to the correction of this error. "However," they continue, "it may be otherwise with exotic ants, for although during the cold of our winters they are generally torpid and need scarcely any food, yet in warmer regions, during the rainy seasons, when they are probably confined to their nests, a store of provisions may be necessary for them."

The author of the article on ants in Smith's Dictionary of the Bible says, in reference to the assertion that ants store seed, that "observation of the habits of ants does not confirm this belief."

Latreille[15] denies it in the following emphatic terms: "N'attribuons pas à la fourmi une prévoyance inutile: engourdie pendant l'hiver, pourquoi formeroit elle des greniers pour cette saison?"

[Footnote 15: Hist. Nat. des Fourmis, 1802.]

Huber again throws the weight of his great authority into the scale against the ants, when he says,[16] "I am naturally led to speak in this place of the manner in which ants subsist in the winter, since we have relinquished the opinion that they amass wheat and other grain, and that they gnaw the corn to prevent it from germinating." He then goes on to show how the ants are frequently torpid during the winter, and that when it happens that a few warmer days wake them up to life, they can always find a few aphides also on the alert; for, strange to say, the same degree of warmth which rouses the ants calls forth the aphides also. It would appear that ants in the northern parts of Europe feed on the honey-dew of aphides, and on animal matter when they can get it; and up to the present time the belief prevails among our modern naturalists that they are limited to the same diet in all parts of Europe.

[Footnote 16: Huber, on Ants, translated by J. R. Johnson, 1820.]

It is now well known, however, that exceptions must probably be made in tropical countries, for the observations of Lieut.-Col. Sykes[17] and Dr. Jerdon[18] have shown that many ants in India collect grain in large quantities, robbing the crops and plants cultivated in gardens, and even stealing seeds put away in drawers, the inference being that they employ them for food. The same observers have recorded how the ants may be seen after wet weather bringing out the grain to dry in the sun.

[Footnote 17: Lieut.-Col. Sykes, Description of New Indian Ants, in Trans. Ent. Soc. Lond., i. 103 (1836), where a single species of ant, which he names _Atta providens_, is described, and its habit of harvesting recorded.]

[Footnote 18: Dr. Jerdon, Madras Journal Lit. and Sc. (1851), where three species are stated to harvest seeds on a large scale--namely, _Œcodoma (or Atta) providens_, _Œcodoma diffusa_, and _Atta rufa_, all of which belong to the same section of ants as our Mentonese harvesters, _Atta barbara_, _Atta structor_, and _Pheidole (or Atta) megacephala_. These very interesting observations of Dr. Jerdon's, as well as those of Lieut.-Col. Sykes, will be found in Appendix B.]

Dr. Lincecum has also given a very interesting account[19] of the habits of the "agricultural ant" inhabiting Texas, _Myrmica (Atta) barbata_, which not only stores the grain of a particular rice-like grass, but is said to maintain a clean crop of this plant around its nest, suffering no weed to appear among it, and harvesting the crop in its proper season.

[Footnote 19: Published in the Journal of the Linnean Society of London, vol. vi. p. 29. 1861.]

The Sauba ant (_Œcodoma cephalotes_) has been seen by Mr. Bates plundering baskets containing mandioca meal (an impure form of tapioca) in Brazil, and this in so wholesale a manner as shortly to threaten the loss of the entire supply; and Dr. Delacoux records[20] the presence in New Granada of a monstrous ant, called by the natives _Arieros_, a word which, I am informed, is of Arabic extraction, and means the _carrier_, which emptied an entire sack of maize belonging to him in a single night.

[Footnote 20: Notice sur les Mœurs et les Habitudes de quelques Espèces de Formiciens des Climats Chauds. Rev. Zool., Mai, 1848, p. 1849.]

It seems strange that while travellers have reported the seed-storing habits of ants in far distant countries, our naturalists at home should have not only remained unaware of its existence in Europe, but even strenuously denied it. It is certain, however, that naturalists and others in southern Europe are more or less aware of the fact, but I have been unable to learn that any accurate account of the habits of harvesting ants has hitherto been published, or that any one has taken pains to discover what becomes of the seed so laboriously obtained.

It is true that in the _Enciclopedia Popolare_[21] extracts are given from the remarks made by M. Gené[22] on the subject, in which he assumes that the fact that ants collect and carry to their nest large supplies of grain and seed is well known, but states that he is at a loss to conceive how they employ them, unless it may be that they use them as materials for the construction of their galleries, for they cannot eat such hard substances, all their food being either liquid or of the nature of juices, "gli alimenti sono sempre materie liquide o materie sugose. Quanto ai corpi duri e secchi che le formiche raccolgono, io non so altrimenti riguardarli che come materiali di costruzione." It will be understood, I think, from what has gone before, that thus far nothing has really been ascertained as to the exact state of the case; for though the Italian author just quoted was aware that certain ants in the Mediterranean region do store seed, his knowledge went no further. Nor am I aware that any French author has published an account of this habit and its object; and in a recent abundantly illustrated volume founded on a work by M. Emile Blanchard, I find, on the contrary, the following very emphatic denial of its existence:--"The curious idea which appears to have commenced in very remote times, and to have been carried down by tradition, and which was assisted by the results of careless observations, concerning the habits of the ants in collecting and storing up provisions, as it were under the influence of a wise foresight, is evidently incorrect."[23] There was, therefore, clearly an opening here for close observation, and this I determined to do my best to supply.

[Footnote 21: Article Formica, vol. v. p. 143-4. (Turin, 1845).]

[Footnote 22: Memorie per servire alla Storia Naturale di alcuni imenotteri, published at Modena, in 1842.]

[Footnote 23: The Transformations of Insects: an adaptation for English readers of M. Emile Blanchard's Metamorphoses, Mœurs, et Instincts des Insectes, p. 196. London. 1871.]

When I set out again from England in October, 1871, on my way to Mentone, I had obtained an idea of some of the leading points which needed to be cleared up, and I was greatly encouraged in my attempt by the interest expressed in the subject by several of our leading naturalists, among whom I may especially mention Mr. Frederick Smith.[24]

[Footnote 24: am very greatly indebted to Mr. Smith for much kind assistance, and especially for having named the specimens which I collected.]

Plainly the first thing to do was to determine whether the seeds which I had watched the ants carry to their nests were separately stored in subterranean granaries, as they would be if the ant really provides for the future; or whether they were merely strewed here and there, or used as building materials.

Next I must, if possible, obtain conclusive evidence as to the use to which the ants put the seeds thus collected; whether they eat them or turn them to some other account. Again I must observe whether the seed-collecting ants also search for aphides, and what other kinds of food they obtain. Then another very interesting question remained--namely, whether all southern ants uniformly collect seed, and to the same extent, or whether the habit is peculiar to certain species.

These, and many other subjects of inquiry connected with them, readily suggested themselves to my mind, and it will now be my endeavour to show how far I have been able to throw light upon them.

The habits recorded in the following pages refer exclusively, unless special notice is given to the contrary, to _Atta barbara_, the black ant represented on Plate I. We have, as far as I am aware, only four _bonâ fide_ harvesting ants on the Riviera--namely, _Atta barbara_ under two forms, the one wholly black the other red-headed; _Atta structor_, a creature very similar to _barbara_, but of a claret-brown colour; and a minute yellow ant, the large workers of which have gigantic heads, named _Pheidole_ (or _Atta_) _megacephala_.

My renewed observations at Mentone were carried on from October, 1871, to May, 1872, and I was able during that interval to become a frequent visitor to a warm and sheltered valley, which lay but a few minutes' walk from the house in which I lived, and in which thirty nests of the most active of the seed-storing ants were to be found.

Full therefore of my intention to resolve this difficulty if possible, I set out on October 29, 1871, immediately after my return to Mentone, to revisit this valley, where, in the previous May, I had seen the ants busily engaged in cutting, carrying, and sorting their harvest.

The spot in question was a rough slope of soft sandstone rock, with accumulations of sandy soil in the hollows, covered with a sparse and scrubby vegetation, composed of _Cistus_ (_C. salvifolius_), pot-herb thyme, black lavender (_Lavandula stæchas_), spiny broom (_Calycotome spinosa_), overshadowed here and there by a few scattered stone and maritime pines, and intermixed with coarse grasses and some smaller plants.

Cultivated lemon terraces lay on the edge of the wild ground lower down in the valley, and at this season, as also in the late spring, these terraces were overgrown with a rank crop of weeds, most of which were in seed.

I had scarcely set foot on the _garrigue_, as this kind of wild ground is called, to distinguish it from meadows or terraced land, before I was met by a long train of ants, forming two continuous lines, hurrying in opposite directions, the one with their mouths full, the others with their mouths empty.

It was easy enough to find the nest to which these ants belonged, for it was only necessary to follow the line of ants burdened with seeds, grain, or entire capsules, which had their heads turned homewards, and there, sure enough, at about ten yards distance, and partly shaded by some small _Cistus_ bushes, lay the nest, to and from the entrances of which the incessant stream of incomers and outgoers kept flowing.

The proceedings of the ants were the same as those previously observed in the late spring (April and May), the workers usually seeking their harvest at some distance from the nest, and going in search of it as far as the cultivated ground, where the crops of weeds were more abundant and more varied.

In a few cases, however, where the terraces were too far distant, they contented themselves with plundering the grasses, pea-flowers, honeywort, and the other denizens of the garrigue. In one case I was able to follow the thread-like column of workers from the nest to the weedy terrace where the plants grew from which they were gathering the seeds, and found that the nearly continuous double line measured twenty-four yards. Even this gives but an inadequate idea of the number of ants actively employed in the service of this colony, for hundreds of them were dispersed among the weeds on the terrace, and many were also employed in sorting the materials and in attending to the internal economy of the nest. Still this affords some evidence of the systematic and extensive scale on which foraging is carried on by this ant, and of the high importance which these creatures attach to their provision of grain.

It is not a little surprising to see that the ants bring in not only seeds of large size and fallen grain, but also green capsules, the torn stalks of which show that they have been freshly gathered from the plant. The manner in which they accomplish this feat is as follows. An ant ascends the stem of a fruiting plant, of Shepherd's-purse (_Capsella Bursa pastoris_) let us say, and selects a well-filled but green pod about midway up the stem, those below being ready to shed their seeds at a touch. Then, seizing it in its jaws, and fixing its hind legs firmly as a pivot, it contrives to turn round and round, and so strain the fibres of the fruit-stalk that at length they snap. It then descends the stem, patiently backing and turning upwards again as often as the clumsy and disproportionate burden becomes wedged between the thickly set stalks, and joins the line of its companions on their way to the nest. In this manner capsules of chickweed (_Alsine media_) and entire calyces, containing the nutlets of Calaminth, are gathered; two ants also sometimes combine their efforts, when one stations itself near the base of the peduncle and gnaws it at the point of greatest tension, while the other hauls upon and twists it. I have never seen a capsule severed from its stalk by cutting alone, and the mandibles of this ant are perhaps incompetent to perform such a task. I have occasionally seen ants engaged in cutting the capsules of certain plants drop them and allow their companions below to carry them away; and this corresponds with the curious account given by Ælian[25] of the manner in which the spikelets of corn are severed and thrown down "to the people below," [Greek: tô dêmô tô katô] τω δἡμω κἁτω.

[Footnote 25: Vide supra, p. 8.]

If the incoming and weight-carrying column of ants be closely examined it will be found that though the great majority of workers are bringing seeds in some form to the nest, a few are burdened with other and more miscellaneous materials.

Occasionally one or two may be detected carrying a dead insect, or crushed land-shell, the corolla of a flower, a fragment of stick, or leaf, but I have never seen aphides brought in to the nest or visited by this ant or by _Atta structor_.

It sometimes happens that an ant has manifestly made a bad selection, and is told on its return that what it has brought home with much pains is no better than rubbish, and is hustled out of the nest, and forced to throw its burden away. In order to try whether these creatures were not fallible like other mortals, I one day took out with me a little packet of grey and white porcelain beads, and scattered these in the path of a harvesting train. They had scarcely lain a minute on the earth before one of the largest workers seized upon a bead, and with some difficulty clipped it with its mandibles and trotted back at a great pace to the nest. I waited for a little while, my attention being divided between the other ants who were vainly endeavouring to remove the beads, and the entrance down which the worker had disappeared, and then left the spot. On my return in an hour's time, I found the ants passing unconcernedly by and over the beads which lay where I had strewn them in apparently undiminished quantities; and I conclude from this that they had found out their mistake, and had wisely returned to their accustomed occupations.

I have often amused myself by strewing hemp and canary seed or oats, all of which form heavy burdens for the ants, near their nests; and it is a curious sight to watch the eagerness and determination with which they will drag them away. It is interesting also to note how on the following day the husks of these seeds will appear on the rubbish-heap, or sometimes, after a shower of rain, they will be brought out by the ants with the point of the little root (the radicle or fibril as the case may be) gnawed off (see Figs. A, B, C, Plate VI., p. 35).

It frequently happens that on the wild hillside the position of a nest of _Atta barbara_ is indicated by the presence of a number of plants growing on or round the kitchen midden, which are properly weeds of cultivation, and strangers to the cistus- and lavender-covered banks of the garrigue. These have sprung from seeds accidentally dropped by the ants, and which they had obtained from the lemon terraces. Thus when you see little patches of ground from one to three feet long and broad, covered with such plants as fumitory (_Fumaria_), oats (_Avena_), nettles (_Urtica membranacea_), four species of _Veronica_, chickweed (_Alsine media_), goosefoot (_Chenopodium_), _Rumex Bucephalephorus_, wild marigold (_Calendula arvensis_), _Antirrhinum Orontium_, _Linaria simplex_, and _Cardamine hirsuta_, you may confidently expect to find a colony of these ants close at hand.

These plants are sometimes found along the sides of miniature gullies and crevices in the rock, where they have been washed by little runlets of water formed in seasons of heavy rain, and thus these interloping plants are occasionally dispersed and brought into competition with the rightful occupiers of the ground.

_Atta structor_ and _A. barbara_ do not employ any materials in the construction of their nest, simply excavating it out of the earth itself, or occasionally out of the sandy rock, and the large mounds, in great part composed of vegetable matter, which may frequently be found at the entrances of their nests, are nothing more than the rubbish heaps and kitchen middens of each establishment. These consist in part of the earth pellets and grains of gravel which the ants bring out from their nest when forming the subterranean galleries, but principally of plant-refuse such as the chaff of grasses, empty capsules, gnawed seed-coats, and the like, which would occupy much space if left inside the nest (see Plate I., Fig. A.). While an army of workers are employed in seeking and bringing in supplies, others are busy sorting the materials thus obtained, stripping off all the useless envelopes of seed or grain, and carrying them out to throw away. Thanks to the unwearied activity with which this divided labour is carried on the kitchen middens speedily rise in the harvest season, and in places where they are not exposed to the action of wind and rain, often acquire a considerable size, so much so that sometimes, if collected, one alone might fill a quart tankard.

It was the sight of such a refuse mound, and an examination of the materials which composed it,--many of which show that they were once parts of seeds, &c., the albuminous contents of which had been extracted through holes gnawed in the side,--that gave me the conviction that large stores of seed must lie hidden below in the nest; for if it were true, as some have suggested, that the ants employ the grain and seeds which they collect as materials for the construction of their nest, they would certainly not reject such parts as the chaff of grasses and the like, which are admirably suited for the purpose, and are actually used for this end by other species of ants.

It was therefore with the greatest confidence as to the result that I opened the nests of _Atta barbara_ in search of granaries and seeds. My first attempt was made upon a nest lying in a hollow where there was a rather deep bed of soil, and the galleries extended so far on either side and in a downward direction that, though I removed enough soil to fill a wheelbarrow, I failed to reach the arcana of the nest, and saw neither chambers nor granaries.

Yet I frequently encountered workers carrying seeds downwards along the subterranean passages. I then selected a nest where the coarse and hard rock lay much nearer to the surface, barring their downward course, and compelling the ants to extend their nest in a horizontal direction.

Here, almost at the first stroke, I came upon large masses of seeds carefully stored in chambers prepared in the soil. Some of these lay in long subcylindrical galleries, and, owing to the presence in large quantities of the black shining seeds of amaranth (_Amaranthus Blitum_, &c.), looked like trains of gunpowder laid ready for blasting. Fig. A, Plate II. represents a trowelful of earth taken from this nest, and lifted with care so as to leave the seeds almost _in situ_. Others were massed together in horizontal chambers, having a concave roof and a flat and carefully prepared floor.

The texture of the floor usually differs markedly from that of the surrounding soil, and the fine grains of silex and mica which are selected for its construction are more or less cemented together, so that the floor will sometimes part, when dry, from the soil about it, as caked and dry mud separates from a gravel path (see Plate III.).

On carefully examining a quantity of the seeds, grain, and minute dry fruits taken from the granaries, I found that they had been gathered from the following plants: fumitory (_Fumaria Capreolata_, &c.), amaranth (_Amaranthus Blitum_, &c.), _Setaria_, and three other species of grasses, honeywort (_Alyssum maritimum_), _Veronica_, and from four unrecognised species, one of which was a pea-flower. There were therefore in this nest seeds, &c., which had been taken from more than twelve distinct species of plants, belonging to at least seven separate families. The granaries lay from an inch and a half to six inches below the surface and were all horizontal. They were of various sizes and shapes, the average granary being about as large as a gentleman's gold watch.

I was greatly surprised to find that the seeds, though quite moist, showed no trace of germination, and this was the more astonishing as the self-sown seeds of the same kinds as those detected here, such as fumitory for instance, were then coming up abundantly in gardens and on terraces. The seeds of _Odontites lutea_ afford a curious test of the presence of moisture in the granaries, and it will usually be found that, when they are recently taken out of the nest, they are of a greenish colour and semi-transparent horn-like texture, which changes on exposure to the air to a chalky white and opaque appearance, due to the drying of the coat of the seed.

The fact of the sound condition of the seeds in these granaries seemed to me so very strange and difficult to explain that I determined to pay special attention to the subject, and with this view collected and carefully examined large quantities of the grain and seeds taken at different times from the stores of twenty-one distinct nests, the first of which was opened on October 29th, and the last on May 5th. In these twenty-one nests out of the thousands of seeds taken I only found twenty-seven in seven nests which showed trace of germination, and of these eleven had been mutilated in such a way as to arrest their growth. The sprouting seeds were found in the months from November to February, while in the nests opened in October, March, April, and May, no sprouted seeds were discovered, though these latter months are certainly highly favourable to germination. It is therefore extremely rare to find other than sound and intact seeds in the granaries, and we must conclude that the ants exercise some mysterious power over them which checks the tendency to germinate.

Apparently it is not that moisture or warmth or the influence of atmospheric air is denied to the seeds, for we find them in damp soil, in genial weather, and often at but a trifling distance below the surface of the ground; and I have proved that the vitality of the seeds is not affected by raising crops of young plants, such as fumitory, pellitory, _Polygonum aviculare_, and grasses, from seeds taken out of granaries.[26]

[Footnote 26: This experiment was tried by me on two occasions, in the former case the seeds were taken from a granary about four inches below the surface of the ground, on November 10th, and sowed two days afterwards, and several of these were up on Dec. 1st. The second trial was made on seeds found at only one and a half inch below the surface, on Dec. 29th, 1871; these were sowed in England on June 18th, 1872, and the young plants made their appearance in large numbers ten days afterwards.]

I have frequently remarked that it is the seeds last collected before a fall of rain which are brought out in a sprouting condition from the nest; for I have observed in cases where I had recently scattered seeds near wild nests, that it is these which are carried out from the nest and placed to dry after a wet night; and so in the case of a nest which I kept in captivity, when a variety of different seeds had been successively supplied to the ants, it was the cabbage, lettuce, and chicory seeds, given the day before the nest was watered, that reappeared after having been carried below, and not the hemp, canary, and mixed seeds of wild plants previously strewed on the nest. It seems possible that the process, whatever it may be, to which the ants subject the seeds which are to remain dormant may require some time, and the construction of the granary chambers is doubtless a long affair, so that when unusually large supplies of grain, &c., are brought in by the workers some part of them may not find the necessary accommodation and attention. When the seeds do germinate in the nests, and it is my belief that they are usually softened and made to sprout before they are consumed by the ants, it is very curious to see how the growth is checked in its earliest stage, and how, after the radicle or fibril--the first growing root of dicotyledonous and monocotyledonous seeds--has been gnawed off, they are brought out from the nest and placed in the sun to dry, and then, after a sufficient exposure, carried below into the nest.

The seeds are thus in effect malted, the starch being changed into sugar, and I have myself witnessed the avidity with which the contents of seeds thus treated are devoured by the ants.

Figs. A, B, C, in Plate VI., p. 35, illustrate the manner in which the ants mutilate the germinating seeds and check their growth. Thus, at Fig. C 2 of Plate VI. a sprouting but uninjured canary seed (_Phalaris canariensis_) is drawn, magnified, and at Figs. C and C 1 the same of the natural size and magnified, after the ants have gnawed its fibril (fib.), which in this case pierces the undeveloped radicle (rad.). Fig. A 2 represents a sprouting hemp-seed, magnified,[27] and Figs. A, A 1, the same of the natural size and magnified, mutilated, the tip of the radicle being removed.

[Footnote 27: Properly a nut, for it comprises the seed and the enveloping coat of the ovary. The canary seed also, spoken of above, is a grain containing a seed.]

At Figs. B, B 1, B 2, the same process is shown in the case of a small wild pea.

It is, however, certain that though a few individual seeds may sprout in the nests from time to time either with or without the concurrence of the ants, the great mass remain for many weeks, or even months, quite intact, neither decaying nor germinating, whereas every one knows that if a quantity of seeds are placed in the soil in a moist and warm place, all the seeds that are of one kind will almost simultaneously begin to grow after the lapse of a fixed interval.

Now if this took place in an ant's nest, the provisions would have to be rapidly consumed at stated periods and to be frequently renewed; but this is not the case. This is easily shown by an examination of the seeds contained in the nests in April or May, many of which will prove to belong to plants which fruit in the autumn and are not to be found later than November. Thus, for example, on May 5th at Cannes, I discovered nutlets of _Cynoglossum pictum_, which can scarcely have been collected later than the preceding October or November. Besides, during the time from the middle of January to the middle of March, scarcely a seed is collected under ordinary circumstances, there being extremely few wild plants in fruit at that season, and yet the granaries will be found well filled if a nest is opened at the end of this period.

A knowledge of the fact that ants in warm climates accumulate large and very varied stores of seeds retaining their power of germination, might at times be of service to travellers, by enabling them to obtain, by a stroke or two of the spade, an interesting collection of the seeds and the seed-like fruits of the country, when time and opportunity failed for obtaining them in a more satisfactory manner. The following list of plants, the grain, seeds, and small dry fruits of which I have found in the subterranean granaries of _Atta structor_ and _A. barbara_, especially the latter, shows that the ants probably collect almost indiscriminately from any fruiting plant that falls in their way.

Fumitory (_Fumaria_, three species), honeywort (_Alyssum maritimum_), narrow-leaved sun rose (_Fumaria viscida_ and _F. Spachii_), _Oxalis corniculata_, _Silene_, _Linum gallicum_, mallow (_Lavatera cretica_?), medick (_Medicago_), wild lentil (_Ervum_), spiny broom (_Cytisus spinosus_), _Valerianella carinata_, _Centaurea aspera_, _Odontites lutea_, _Calamintha Nepeta_, _Polygonum convolvulus_ and _P. aviculare_, amaranth (_Amaranthus Blitum_ and _patulus_), pellitory (_Parietaria_), _Euphorbia_, pine (_Pinus_), wild sarsaparilla (_Smilax aspera_), _Setaria verticillata_ and _S. italica_, _Andropogon Ischæmum_, and of eight other plants of which I do not recognise the seeds. This list, comprising plants belonging to eighteen distinct families, might be greatly prolonged if I were to add to it the names of the seeds which I have seen the ants carry towards their nests, but have not actually detected in the granaries. Thus I have seen trains of ants burdened with the long-beaked, spirally-twisted fruits of crane's bill (_Erodium_), and, as above mentioned, with capsules of chickweed (_Alsine media_) and shepherd's-purse (_Capsella Bursa pastoris_), with whole orange pips, and even haricot beans, seeds of the New Zealand veronica (_V. Andersonii_), of _Silene pseudoatocion_, and many other garden plants, also with nutlets of the plane tree and seeds of the cypress.

Pliny mentions[28] incidentally having watched the ants carrying away cypress seeds, and comments upon the fact that so small a creature should be able to interfere with the growth of such a noble tree.

[Footnote 28: Pliny, Nat. Hist., xvii. 14, 3.]

I have little doubt that the seed stores of the ants in botanic and other gardens, where rare plants are cultivated in southern Europe and in warm climates generally, contain samples taken from the fruits of a great many of the rarer and more interesting species as well as of the weeds and native plants. Indeed I have been told that this is the case by my friend Dr. Bornet, who complains of the depredations committed by the ants in the gardens of the Villa Thuret, at Antibes. They go so far as to plunder the seed bags which are hung from the branches of the trees and shrubs, unless these are securely closed and tied with string; they carry off wholesale the grass and anemone seeds,[29] which are scattered when the lawns are resown; and Dr. Bornet has seen the seeds of _Acacia retinoides_ lie heaped up by the handful at the entrances of their nests, and disappear below after a few hours.

[Footnote 29: Properly grass grain and anemone achenes.]

M. Germain de St. Pierre has observed similar facts at Hyères, where he has detected large stores of cereals in the granaries of the ants, and considers that the robberies committed by these creatures are sufficient in extent to cause a serious loss to cultivators.

It is difficult to estimate the amount of seed stored in a single nest by a colony of ants both on account of the extent of these nests, and because of the number of seeds which are always lost in digging. The nests themselves also vary greatly in size. Perhaps I shall not be very far from the mark however, if I conjecture that average-sized nests contain during the winter months about half a pint of seeds.

_Atta structor_ is more frequently found near houses and in gardens than _A. barbara_, the latter usually living on wild ground adjoining cultivation. There was a flourishing colony of _structor_ in the main street of Mentone, cleverly placed at the lintel of the door of a corn chandler's store, where they were ever on the look out for stray grains of oats and wheat, which might chance to fall from the sacks. Another nest, in a different part of the town, got its principal subsistence from the grains of canary seed, which were scattered by the birds occupying a cage hanging outside a shop window at a little distance.

The granaries of _A. structor_ are arranged in the same way as those of _A. barbara_, and may, in like manner, be found stored with seeds, and lying at depths below the surface, varying from one to twenty inches.

A diagram is given in the preceding woodcut of a vertical section of a nest of _barbara_ lying in soil sixteen inches deep, the granaries being at 1-1/2, 2, 4, 6, 9, and 12-1/2 inches, as determined by actual measurement on the spot.

In some cases, and especially where the soil is shallow, the galleries and granaries are much crowded together, as is shown in Plate IV., which represents a small mass of earth, pierced by the roots of plants, taken out of a nest of _barbara_, lying at two inches below the surface. When first opened all these granaries were filled with seeds.

The shape of the granary chambers varies considerably, as may be seen by reference to the drawing of three floors given in Plate III., p. 23, and that shown diagrammatically in the woodcut on next page, where the white space represents the granary floor, and the dark circular spot in the centre, the aperture of a gallery leading downwards.

I once had an opportunity of seeing a large portion of a nest of the red-headed variety of _barbara_ laid bare by a cutting recently made through a bank at Cannes in digging the foundations of a house, which exposed a very extensive and complicated series of galleries and granaries. The lowest point at which I detected the workings of the ants was at twenty inches below the surface of the ground, and here granaries containing seeds in abundance were present, and the galleries and granaries extended over a space measuring 5ft. 9in. in a horizontal direction. In two cases I have found nests of _Atta barbara_ at Mentone which were carried far into the living rock in places where it happened to be of an even grain, and not gritty or pebbly as it frequently is. It was quite by chance that I first discovered this very interesting fact, having tracked a train of seed-bearing workers to a part of the sandstone rock where steps had quite recently been hacked out leading to some terraces.

I soon saw that the ants entered and came out from three or four small passages in the cleft surface of the rock, and that their nest actually lay in the sandstone itself. Having contrived to wedge off several large flakes of the rock, which was soft in most places and might be scooped out with a strong knife, I discovered that though some of the passages of the ants followed the lines of cleavage and the cracks made by the fine wiry fibres of the bushes growing on the surface, others were frequently made in the form of tubular tunnels through the living rock. Without the aid of hammer and chisel it was not possible to follow the galleries and to secure specimens of the mined rock; but on the next day (Dec. 7th) I returned armed with tools, and with the assistance of a friend[30] quarried out a portion of the nest, tracing it down eventually to twenty-three inches below the surface of the rock in a vertical, and to about sixteen inches away from the surface in a horizontal direction.

[Footnote 30: I take this opportunity of expressing my thanks to Mr. Robert Lightbody for help on this and other occasions.]

At one point where the rock was almost entirely solid and without flaw or crevice, and where it was clear that the passages were entirely the work of the ants, we measured a tunnel by worming a straw down it, and found it to be ten inches in length. We subsequently traced this tunnel or rock gallery down until it communicated with a chamber filled with winged ants and seeds of several kinds. This granary was horizontal, and merely an enlargement of an ordinary gallery of a compressed spindle-shape, flattened from above downwards, measuring as nearly as I could estimate three inches in length, by a trifle less than an inch in breadth, and half an inch in height. The walls were tolerably smooth, but not prepared or glazed in the way that certain small terminal cells which I shall shortly describe were. The surfaces, however, had a very different appearance to that of the surrounding sandstone, being of a darker and brownish colour, and seeming to be coated with some kind of dressing or cement.