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Show 198 INSTINCT. [CHAP. VII. bours with surpr1~1n9 courage. Now I was curious to ascertain whether :B. sanguinea could distinguish the pupre of F. fusca, which they habitually n1ake into slaves, from those of the little and furious F. flava, which they rarely capture, and it was evident that they did at once distinguish thmn: for we have seen that they eagerly and instantly seized the pupre of F. fusca, whereas they were 1nuch terrified when they can1e across the pupre, or oven the earth from the nest of F. flava, and quickly ran away· but' in about a quarter of an hour, shortly after all th~ little yellow ants had crawled away, they took heart and carried off the pupre. . One evening I visited another community of F. sangunlea, and found a nu1nber of these ants entering their ~1est, carrying t~1e d~ad bodies of F. fusca (showing that It was not a m1gration) and nu1nerous pupre. I traced the returning file ?urthened with booty, for about forty yard.s, t? !1 very tlnck clurr;p of heath, whence I saw the last Ind1v1dual of F. sangun1ea emerge, carrying a pu.pre; but I was not able to iind the desolated nest in the thick heath. The nest, however, must have been close at hand for two or three individuals of F. fusca were rushing about in the greatest agitation, and one was perched mo- . tionless with its own pupa in its mouth on the top of a spray of heath over its ravaged home. . . Such are. the facts though they did not need confirmation by me, 1~ regard to the wonderful instinct of making slaves. Let 1t be observed what a contrast the instinctive habits of F. sanguinea present with those of the F. rufescens. The latter does not build its own nest does not determine its own migrations, does not collect food for itself or its young a:nd cannot even feed itself:. it is absolutely dependent on Its numerous slaves. Formica sanguinea, on the other hand, possesses much fewer slaves, and in the early ~art of the summer extremely few. The masters determine when and where a nevv nest shall be for1ned and when they migrate, the masters carry the slaves~ Both in Switzerland and England the slaves seem to have the exclusive care of the larvre, and the masters alone go on slave-making expeditions. In Switzerland the slaves CHAP. VII.] CELLS OF THE ITIVE-BEE. 199 and n1asters work together, making and bringing Inaterials for the nest : both, but chiefly the slaves, tend, and milk as it m3y be called, their aphides ; and thus both collect food for the com1nunity. In England the masters alone usually leave the nest to collect building materials and food for themselves, their slaves and larvre. So that the masters in this country receive much less service from their slaves than they do in Switzerland. By what steps the instinct of F. sanguinea . ori~inated I ·will not pretend to conjecture. But as ants, whiCh are not slave-makers, will, as I have seen, carry off pupre of other species, if scattered near their nests, it is possible that pupre originally stored as food might become developed ; and the ants thus unintentionally reared would then follow their proper instincts, and do what work they could. If their presence proved useful to the species which had seized them-if it were more advantageous to this species to capture workers than to procreate them-the habit of collecting pupre originally for food might by natural selection be strengthened and rendered permanent for the very different purpose of raising slaves. When the instinct was once acquired, if carried out to a much less extent even than in. our British F. sanguinea, which, as we have seen, is less aided by its slaves than the same species in Switzerland, I can see no difficulty in natural selection increasing and modifying the instinct-always supposing each modification to be of use to the speciesuntil an ant was formed as abjectly dependent on its slaves as is the Formica rufescens. Cell-making instinct of the Hive-Bee.-I will not here enter on minute details on this subject, but will merely give an outline of the conclusions at which I have arrived. He must be a dull man who can examine the exquisite structure of a comb, so beautifully adapted to its end, without enthusiastic admiration. We hear from mathematicians that · bees have practically solved a recondite problem, and have made their cells of the proper shape to hold the greatest possible amount of honey, with· the least possible consumption of precious wax in their con- -struction. It has been remarked that a skilful workman, |