Page:Popular Science Monthly Volume 3.djvu/167

Rh of man. Yet the European beaver and the oriole give us examples of instincts that go back to a date relatively not very ancient. We know now, too, that the nests of the same species of birds sometimes present remarkable enough variations in different countries. That Darwin should point out with great care these instincts, varying with latitudes, is very natural; but we should less naturally expect to find a similar fact, in the book of a partisan, of the unchangeableness of instincts. The leaf-cutter, another hymenopterous insect, lays its eggs in little chambers made of bits of leaves which it has rapidly cut. In our country it is always a rose-leaf. Yet, "we are assured," says M. Blanchard, "that our cutter of rose-leaves, finding itself in some place in Russia where there are no rose-bushes, makes its nest with willow or osier leaves." Therefore, instinct must vary in space as it has varied in time! It is not at all the case that the same legionaries are everywhere as dependent on their comrades as those that Peter Huber saw in the environs of Geneva. In England, as in Switzerland, the auxiliaries reared by the dark-red ants take complete care of the larvae, while the legionaries alone go on expeditions; but in Switzerland the two castes together busy themselves about all works of construction or supply, while in England the legionaries alone go out to gather provisions and materials; the auxiliaries remain shut up within; they thus render less service to the community than they do in Switzerland.

It will be said, perhaps, that these differences are a very trifling matter. They are, at least, enough to show how the ancient doctrine of Cuvier has been shaken, and how, in the infinite lapse of time, those instincts may have become developed, which mere geographical accidents suffice to modify slightly. The grand solution of instinct is—Time; that immeasurable duration of those geological epochs which our mind holds in contemplation, but of which it can no more form an idea than of the measure of the heavenly spaces. Modern science begins to be amazed at those figures of ages which it must count since the rude attempts at primitive human industry. What shall we think of those times, measured by the planet's growth, through which the instinct of the legionary ants may have been originated, defined, and perfected? The ant not only saw the epoch of the reindeer and the mammoth, and the glaciers of the Jura creeping down the valley of the Rhone—it was a contemporary of that period which geologists mark by the lifting of the Alps. The ant is older on the earth than Mont Blanc. They existed already in the Jurassic period, very little different from what they are in our own times. While an inland sea still flowed over the site where later Paris was to stand, they were multitudinous in the central regions of Europe that were out of water. We may judge of this by the mass of their remains; they fill thick layers of territory at Oeningen, on the shores of Lake Constance, and at Radoboj, in Croatia; the rock is black with ants, all wonderfully preserved, with their claws and delicate antennae. Entomologists now