Page:Popular Science Monthly Volume 71.djvu/560

554 of workers, as in the case of most ants. Santschi has recently made the illuminating discovery that the queen Bothriomyrmex, after entering the nest of Tapinoma, actually decapitates the queen of the host species and is adopted in her stead. In the other cases the disappearance of the host queen has not been accounted for. In the case of F. incerta it is conceivable that she may be ejected from the colony or be killed by her own workers as in the colonies of the Algerian Monomorium salamonis infested with Wheeleriella, a case to be considered presently. For the consocians type of social parasitism Santschi has suggested the name "tutelary" parasitism, because the young of this species are reared by workers older than the parasitic queen.

3. Slavery, or Dulosis.—In this case, as I have shown for the American F. sanguinea the female enters a Formica colony belonging to some variety of the F. fusca or schaufussi group, kills or puts to flight the workers that attack her and hastily appropriates a number of worker larvæ or cocoons. These she carefully guards till they hatch, when she is surrounded by a loyal brood—of an alien species, to be sure, but nevertheless both able and inclined to bring up her brood when it appears. This is "pupillary" parasitism, to use Santschi's term, since the nurses, or host ants, are younger than the parasitic queen. In this case the queen of the host species is probably put to flight at the time the sanguinea queen enters the nest. Polyergus rufescens colonies are, perhaps, founded in the same manner, but unequivocal observations on the queens of this species are still lacking. Not only is slavery, at least as manifested in sanguinea, distinguished from the other forms of social parasitism by the aggressive behavior of the queen, but also by a peculiarity of her own workers. These inherit from their mother the instinct to enter nests of the host species, and appropriate the young, but these queen instincts are intimately associated with the feeding instincts of the workers, as the latter forage in companies like so many nondulotic ants and consume many of the captured pupæ. Hence the futility of all attempts, like those of Darwin and Wasmann, to understand slavery from a study of the behavior of the workers alone.

Wasmann and Santschi believe that slavery has arisen from temporary parasitism, but although I myself first advanced this opinion, I have been compelled to abandon it. "Wasmann found that a colony of Formica truncicola, which he has shown to be a temporary social