PART I.
HARVESTING ANTS.
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]
[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]
[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.