A still more extraordinary instance of a slave-holding species of ant than the one just mentioned is _Anergates atratulus_, for in this there are no workers at all, only kings and queens, who are waited on, and their eggs and larvæ fed and tended, by the slave species—_Tetramorium_, in this case also—just as though these latter were their true-born subjects. Here too the slave species is only represented by workers. These male and female _Anergates_—a worker of the species has never been known—are both few in number and weak in themselves. When a pair of them (or a fertilised queen) go off to found a new colony, how do they, or how do their few weak descendants, impress a strong fierce species into their service, by whom the nest is built, and every other service performed? The question remains unanswered. Nobody knows. Several theories have been advanced, one by Sir John Lubbock, who supposes that the king and queen of _Anergates_ assassinate the queen of _Tetramorium_ and reign in her stead,[54] and another, more recently, by Wasmann, whose idea is that fertile queens of _Anergates_ are sometimes adopted by a colony of _Tetramoriums_ who have lost their own queen. This last is the newest suggestion, and is considered just at present, perhaps for that reason, the most probable. To me Sir John Lubbock’s view seems likelier to be correct, since it is more usual in nature for the weak to prey, as parasites, upon the strong, than for the strong to seek assistance of the weak. True, I can form no idea as to how the assassination of the rightful queen takes place, but Nature is full of resources, and will do much to promote a really worthy end.