Chapter IX: Introduction (6)

In another spot, several stems of a thistle, loaded with pucerons, rose from the very centre of an ant-hill, inhabited by Brown Ants, who, availing themselves of the particular disposition of the leaves of this plant, had constructed around the branches, several little oblong houses, where they came to procure their food. On my destroying one of these houses, the ants carried off immediately into their nest the little animals they so much valued. A few days after, I saw it repaired, and the cattle brought back to their paddock. These houses are not always constructed close to the ground: I saw one once five feet above the surface, which merits being described; it consisted of a short blackish tunnel, which surrounded a small branch of a poplar-tree, at that place where it quitted the trunk. The ants arrived at this spot by passing through the interior of the tree, which was hollow, and thus screened from observation, they reached their pucerons by an opening at the beginning of the branch. The tunnel was formed of decayed wood, and of the earth about the tree. I saw several ants engaged in bringing pellets in their mouths, to repair the breaches I had made. These proceedings are by no means of common occurrence; we cannot attribute them to an habitual routine.

There are some ants who receive their nourishment from the pucerons inhabiting the common plantain: they are generally stationed under the flower; but when this falls to the ground, and the stem withers, which happens about the end of August, they retire for shelter under the radical leaves of the plant; the ants follow, and enclose them, by _walling_ up with moist earth all the space between the ground and the margin of the leaves; they afterwards excavate the ground, to have more room to approach these insects, and pass from thence to their habitation, by covered galleries.

5. _Resources of the Ants during Winter._

I am naturally led to speak in this place, of the manner in which ants subsist in winter, since we have relinquished the opinion that they amass wheat and other grain, and that they gnaw the corn to hinder it from germinating. We have endeavoured to explain their preservation, by supposing them to fall into a state of torpor at this period. They, in fact, become torpid during the intense cold, but when the season is not very severe, the depth of their nest guards them from the effects of the frost: they do not become torpid, unless the temperature is reduced to the second degree of Reaumur under the freezing point, (27° Fahrenheit.) I have occasionally seen them walking upon the snow, engaged in their customary avocations. In so reduced a temperature, they would be exposed to the horrors of famine, were they not supplied with food by the pucerons, who, by an admirable concurrence of circumstances, which we cannot attribute to chance, become torpid at precisely the same degree of cold as the ants, and recover from this state also, at the same time: the ants, therefore, always find them when they need them.

Those ants that do not possess the knowledge of the mode of assembling these insects, are, at least, acquainted with their retreat; they follow them to the feet of the trees, and the branches of the shrubs they before frequented, pass at the first degree of frost along the hedges, following the paths which conduct to these insects, and bring back to the republic a small quantity of honey; a very little sufficing for their support in winter.

As soon as the ants recover from their torpid state, they venture forth to procure their food. The aliment contained in their stomach is, on their return, equally distributed to their companions. These juices scarcely evaporate, during this season, owing to the thickness of the horny rings investing the body. I have known ants preserve, during a considerable time, their internal stock of provisions, when they could not impart it to their companions. When the cold increases in a gradual manner, (and this is commonly what the ants experience who are screened from it by a thick wall of earth,) they collect and lie upon each other by thousands, and appear all hooked together. Is this done, in order to provide themselves a little heat? I presume this to be the case, but our thermometers are not sufficiently delicate to indicate if this be really the fact.

6. _Of the Eggs of the Pucerons._

The pucerons, which are viviparous in the summer, are oviparous during Autumn. This very remarkable fact is here most fully confirmed.[5] One day, in November, anxious to know if the Yellow Ants began to bury themselves in their subterranean chambers, I destroyed, with care, one of their habitations, story by story. I had not advanced far in this attempt, when I discovered an apartment containing an assemblage of little eggs, which were for the most part of the colour of ebony. Several ants surrounded, and appeared to take great care of them, and endeavoured, as quickly as possible, to convey them from my sight. I seized upon this chamber, its inhabitants, and the treasure it contained.

[5] Although these insects are both oviparous and viviparous, yet this is not the greatest singularity in their history, for they will produce, as fully confirmed by Bonnet and other celebrated naturalists, several young in succession, without intercourse with the male insect. The common gnat, it is asserted, will produce young, and these, in their turn, will give birth to others, down to the sixth generation, without further intercourse with the male. Huber, the father of our present author, so well known to us from his extensive discoveries in natural history, thinks, that one impregnation is sufficient to render fertile all the eggs which a queen bee may produce in the whole course of her life, usually about two years. And Mons. Audibert has known a female spider produce young, for several successive generations, from one single impregnation of the male. The circumstance of the _Aphides_, or _Pucerons_, being oviparous or viviparous, seems to depend upon the prevailing temperature. Mr. Curtis having remarked the same species to be oviparous in the open air, which when sheltered from the wind, in a green-house, was viviparous. The wood-louse, it has been remarked, sometimes produces its young in the state of an egg, sometimes brings them forth perfectly alive. Redi also mentions a similar circumstance, in his work on the generation of insects, in reference to some of the flies he describes.--T.

The ants did not abandon these eggs to make their escape; a stronger instinct retained them: they hastened to conceal them under the small dwelling, which I held in my hand, and when I reached home, I drew them from it, to observe them more attentively. Viewed with a microscope, they appeared nearly of the form of ants’ eggs, but their colour was entirely different; the greater part were black; others were of a cloudy yellow. I found them in several ant-hills, and obtained them of different degrees in shade; they were not all black and yellow; some were brown, of a slight, and also of a brilliant red and white; others were of a colour less distinct, as a straw colour, greyish, &c. I remarked they were not of the same colour at both extremities.

To observe them more closely, I placed them in the cover of a box faced with glass; they were collected in a heap, like the eggs of ants; their guardians seemed to value them highly; after having visited them, they placed one part in the earth, but I witnessed the attention they bestowed upon the rest: they approached them slightly separating their pincers, passed their tongue between each, extended them, then walked alternately over them, depositing, I believe, a liquid substance as they proceeded. They appeared to treat them exactly as if they were eggs of their own species; they touched them with their antennæ, and frequently carried them in their mouths; they did not quit these eggs a single instant; they took them up, turned them, and after having surveyed them with affectionate regard, conveyed them, with extreme tenderness, to the little chamber of earth I had placed at their disposal. They were not, however, the eggs of ants; we know that these are extremely white, becoming transparent, as they increase in age, but never acquire a colour essentially different.[6] I was, for a long time, unacquainted with the origin of those of which I have just spoken, and by chance, discovered they contained little pucerons; but it was not these individual eggs I saw them quit, it was other eggs, which were a little larger, found in the nests of Yellow Ants, and of a particular species. On opening the ant-hill, I discovered several chambers, containing a great number of brown eggs, the ants were extremely jealous of them, carrying them away, and quickly too, to the bottom of the nest, disputing and contending for them with a zeal which left me no doubt of the strong attachment with which they regard them.

[6] Gould has taken notice of these black eggs, which he considers to be the female eggs of ants: here, however, he labours under a mistake, for they are evidently the eggs of the _Aphides_, or _Pucerons_. We learn from Mr. Kirby, that in a nest of yellow ants, which fell under his observation, he saw near the surface a parcel of the eggs of the Aphides, and these he knew by their black colour.--T.

Desirous of conciliating their interests, as well as my own, I took the ants and their treasure, and placed them in such a manner that I might easily observe them. These eggs were never abandoned. The ants took the same care of them as the former. The following day I saw one of these eggs open, and a puceron fully formed, having a large trunk, quit it. I knew it to be a puceron of the oak: the others were disclosed a few days after, and the greater number in my presence. They set immediately about sucking the juice from some branches of the tree I gave them, and the ants now found, within their reach, a recompense for their care and attention.

The ant-hill, whence these eggs had been taken, was situated at the foot of an oak, which readily accounts for their existence in that place. I discovered them in the spring; the pucerons which quitted them were very large, for insects just born, but they had not yet obtained their full size. M. Bonnet, to whom we are indebted for many important discoveries upon the pucerons and their generation, speaks of their eggs, which he has often seen affixed to the branches of trees; he believes that the insect, in a state nearly perfect, quits the body of its mother in that covering which shelters it from the cold in winter, and that it is not, as other germs are, in the egg, surrounded by food, by means of which it is developed and supported. It is nothing more than an asylum of which the pucerons born at another season have no need: it is on this account some are produced naked, others enveloped in a covering. The mothers are not then truly oviparous, since their young are almost as perfect as they ever will be, in the asylum in which Nature has placed them at their birth. M. Bonnet vainly attempted to preserve these kind of eggs in his chamber until the spring; he imagines, that to have attained this end, they should have been kept in a certain degree of humidity, which would have happened to them in a state of nature.

It appears, then, that ants know every thing that is necessary to the preservation of these eggs; they pass their tongue constantly over them, and invest them with a glutinous matter, which retains them together. They, in consequence, are preserved until the period when the pucerons quit them: they employ then the same means to preserve their covey, if I may use this expression, that M. Bonnet supposed would preserve these eggs, and secure their disclosure in the spring. We have reason to believe that this celebrated man would have admired with us this part of their industry, if natural history had not lost in him her most worthy contemplator.