Page:Popular Science Monthly Volume 71.djvu/563

Rh sublæis (parasitic on Leptothorax acervorum) and in North America by T. americanus (parasitic on L. curvispinosus). The former was supposed by Adlerz to have only ergatoid, or worker-like females, but Viehmeyer has recently found winged females as well, and I had previously shown that such individuals exist in our American form. The workers of both species resemble those of Polyergus and Strongylognathus in having blunted or obsolete domestic instincts. Adlerz's observations seem to indicate that the European Tomognathus may be dulotic, but they do not altogether preclude the possibility of permanent parasitism. As there are no observations on the behavior of the recently fecundated queens, it is impossible to decide whether the form of symbiosis exhibited by these ants arose from dulosis or from temporary parasitism or merely from a condition of xenobiosis like that of the North American Leptothorax emersoni or the European Formicoxenus nitidulus.

The accompanying diagram will serve to illustrate the phylogenetic relationships of the different types of colony formation among ants as formulated in the preceding paragraphs.

The foregoing discussion shows very clearly that a rational explanation of slavery among ants can be found only by recognizing the phenomenon as a form of parasitism. This conclusion is indeed forced upon us by a comparative study of the various allied forms of social symbiosis, of the ontogeny of the ant-colony, that is, of the way in which it is started and develops, and by a study of the instincts of the queen. We myrmecologists seem to have been hampered in reaching this conclusion by a knowledge of the habits of the queen honey-bee. This insect is peculiar in being permanently and exclusively in the adoptive