Page:Popular Science Monthly Volume 71.djvu/561

Rh in all essential respects like F. consocians, would accept and rear fusca pupæ placed in the nest. This, however, is not dulosis. In order to establish his case he would have to prove that the truncicola workers can also make periodical forays on fusca for the sake of capturing their young, and there is no more evidence that truncicola can do this than there is of similar behavior on the part of consocians. Santschi, if I understand him correctly, believes that the sanguinea colony restricts its forays to the scattered fragments of the original fusca colony from which the queen secured her first supply of auxiliaries, and that the slave-making expeditions cease when these fragments are exhausted. This assumption seems to explain the fact that old sanguinea colonies are sometimes slaveless and pure, like the adult colonies of consocians, truncicola, etc. It is, however, rendered highly improbable by the fact that both in Europe and in North America sanguinea colonies not infrequently contain slaves of two or more different species or varieties. There is also some evidence that the same colony may have slaves of different species at different times. Professor Forel recently showed me near Morges, Switzerland, a colony of Polyergus which in 1904 contained only F. rufibarbis, but during the current year contained only F. glebaria. The similarity between old sanguinea colonies and adult colonies of temporary parasites like F. consocians, is more probably the result of two very different processes: in the former case of a languishing or lapsing of the slave-making instincts with age, in the latter, as I have shown, of a gradual extinction of the tutelary workers.

3. Permanent Social Parasitism.—This occurs in the following rare and monotypic Myrmicine ants: the European Anergates atratulus, parasitic on Tetramorium cæspitum, the Tunisian Wheeleriella santschii, parasitic on Monomorium salomonis, the North American Epœcus pergandei (on Monomorium minutum var. minimum), Sympheidole elecebra (on Pheidole ceres) and Epipheidole inquilina (on Ph. pilifera coloradensis). All these parasites are unique among ants in lacking a worker caste, so that they are compelled to live permanently with their respective host species. Santschi has recently shown that the justfecundated queen of Wheelenella enters a Monomorium colony and is adopted by the workers, which then actually proceed to kill their own queen. The same conditions probably obtain also in the other cases, as the parasitic queens are too feeble to assassinate the host queen after the manner of Bothriomyrmex. In Anergates the degeneration of the species as a result of permanent parasitism is extreme: the male is reduced to an apterous, pale and anæmic, sluggish, pupa-like creature which mates in the maternal nest with its own sisters (adelphogamy),