unparalleled and inexplicable, for only workers of the _Tetramorium_ are found in company with the ♂ and ♀ _Anergates_; the community, in fact, consisting of males and females of one species and workers of another. The nests of _Anergates_ are so rare that only a few naturalists have been able to observe them (Schenk, von Hagens, and Forel may be specially mentioned), but in the spots where they occur, nests of the _Tetramorium_, containing all the forms of that species, are numerous, and it therefore seems probable that a young fertile female of the _Anergates_ may leave a nest in which it was born, enter a nest of the _Tetramorium_, and, destroying the queen thereof, substitute herself in the place of the victim; but if this be really the case, the larvae and pupae of the _Tetramorium_ must also be destroyed, for no young of the _Tetramorium_ are ever found in these strange associations. It is very difficult to believe that the _Tetramorium_ workers should be willing to accept as their queen a creature that commenced her acquaintance with them by destroying their own queen or queens and a number of their young sisters; especially as the _Tetramorium_ is a more powerful ant than the _Anergates_, and could readily dispose of the murderous intruder if it were disposed to do so. It is known, however, that colonies of _Tetramorium_ completely destitute of queens sometimes occur, and Wasmann has suggested that the female _Anergates_ may seek out one of these, and installing herself therein as a substitute, may be accepted by the orphaned colony. This plausible hypothesis has still to be verified. The genus _Cardiocondyla_ also exhibits the phenomenon of apterous, worker-like males, while in one species, _C. emeryi_, a winged male is also known to exist.