some of their larvæ and pupæ. Under these circumstances it occasionally happens that the pupæ come to maturity in the nests of the horse ant, and nests are sometimes, though rarely, found in which with the legitimate owners there are a few F. fuscas. With the horse ant this is, however, a very rare and exceptional phenomenon; but with an allied species, F. sanguinea, a species which exists in our southern counties and throughout Europe, it has become an established habit. The F. sanguineas make periodical expeditions, attack neighboring nests of F. fusca, and carry off the pupæ. When the latter come to maturity, they find themselves in a nest consisting partly of F. sanguineas, partly of F. fuscas—the results of previous expeditions. They adapt themselves to circumstances, assist in the ordinary household duties, and, having no young of their own species, feed and tend those of the F. sanguinea. But though the F. sanguineas are thus aided by the F. fuscas, they have not themselves lost the instinct of working. It seems not improbable that there is some division of functions between the two species, but we have as yet no distinct knowledge on this point, and at any rate the F. sanguineas can "do" for themselves, and carry on a nest, if necessary, without slaves.
In another species, however, Polyergus rufescens, which is not British, this is not the case. They present a striking lesson of the degrading tendency of slavery, for they have become entirely dependent on their slaves. Even their bodily structure has undergone a change: their mandibles have lost their teeth, and have become mere nippers—deadly weapons, indeed, but useless except in war. They have lost the greater part of their instincts: their art, that is, the power of building; their domestic habits, for they take no care of their own young, all this being done by the slaves; their industry—they take no part in providing the daily supplies; if the colony changes the situation of its nest, the masters are all carried by the slaves to the new one; nay, they have even lost the habit of feeding. Huber placed thirty of them, with some larvæ and pupæ, and a supply of honey, in a box.
This observation has been fully confirmed by other naturalists. However small the prison, however large the quantity of food, these
- Huber, "Natural History of Ants."