Page:Popular Science Monthly Volume 19.djvu/524

consequent value which they set upon them, induce the animals, when supplies are scarce, to plunder one another's nests, prolonged warfare being the result. Thus Moggridge says: "By far the most savage and prolonged contests which I have witnessed were those in which the combatants belonged to two different colonies of the same species. . . . The most singular contests are those which are waged for seeds by A. barbara, when one colony plunders the stores of an adjacent nest belonging to the same species; the weaker nest making prolonged, though, for the most part, inefficient attempts to recover their property." In one case the predatory war lasted for forty-six days, during which time it became evident that the attacking nest was the stronger, for

streams of ants laden with seeds arrived safely at the upper nest, while close observation showed that very few seeds were successfully carried on the reverse journey into the lower or plundered nest. Thus, when I fixed my attention on one of these robbed ants surreptitiously making its exit with the seed from the thieves' nest, and having overcome the oppositions and dangers met with on its way, reaching, after a journey which took six minutes to accomplish, the entrance to its own home, I saw that it was violently deprived of its burden by a guard of ants stationed there apparently for the purpose, one of whom instantly started off and carried the seed all the way back again to the upper nest. . . . After the 4th of March I never saw any acts of hostility between these nests, though the robbed nest was not abandoned. In another case of the same kind, however, where the struggle lasted thirty-two days, the robbed nest was at length completely abandoned.

Lastly, McCook records the history of an interesting engagement which he witnessed between two nests of Tetramorium cæspitum in the streets of Philadelphia, and which lasted for nearly three weeks. Although all the combatants belonged to the same species, friends were always distinguished from foes, however great the confusion of the fight. This fact is always observable in the case of battles between nests of the same species, and McCook thinks that the distinction appears to be effected in some way by contact of antennæ.

Keeping Pets.—Many species of ants display the curious habit of harboring in their nests sundry kinds of other insects, which, so far as observation extends, are of no benefit to the ants, and which have therefore been regarded by observers as mere domestic pets. These pets are, for the most part, species which occur nowhere else except in ants' nests, and each species of pet is peculiar to certain species of ant. Beetles and crickets seem to be the more favorite kinds of insects, and these live on the best terms with their hosts, playing round the nests in fine weather, and retiring into them in stormy weather, while allowing the ants to carry them from place to place during migrations. It is evident, therefore, that ants not only tolerate these insects, but foster them; and, as it seems absurd to credit the ants with any mere fancy or caprice, such as that of keeping pets, it is per-