THE COMPOUND NESTS. 



435 



x 



sions the inquilines seize them by their mandibles, antennae or legs and 

 try to force them to withdraw. Then the broken walls are rebuilt by 

 the inquilines and new entrances are made into the Mynnica galleries 

 at other points. When colonies of both species, together with their 

 brood, are placed in nests containing no earth, the Leptothora.v collect 

 all their young in a pile and act towards any Myrmica that approaches 

 them as they do when their earthen cells are invaded. For days the 

 little ants struggle to maintain the integrity of their exposed nursery 

 and even build around it ramparts of sugar or other substances which 

 they may find in the nest, but the intrusions of the Mynnica become so 

 frequent and insistent that they finally give up and allow their larvae and 

 pupae to become mingled with those of their host. As soon as this occurs 

 the ants no longer form a compound nest, but a mixed colony. While 

 the two species are living 

 together the Leptothora.v 

 never approach the food 

 dish or feed independently, 

 but if a colony of this 

 species is isolated the 

 workers begin to visit the 

 food and feed, rather awk- 

 wardly at first, but even- 

 tually quite like ordinary 

 ants. This indicates that 

 the symbiosis between the 

 two species must be of 

 comparatively recent de- 

 velopment. In natural 

 colonies the feeding of the 

 inquilines does not seem to 

 constitute a serious drain 

 on the hosts, as the latter, 

 even when supporting a 

 few hundred of the little 

 satellites, are nevertheless 



FIG. 261. Lefitothora.v emersoni and Myr- 

 mica canadensis. (Original.) The two largest 

 ants are workers of M. canadensis ; in the lower 

 middle portion of the figure a worker L. emer- 

 soni; in the vertical row to the right, a male, 

 dealated female, ergatoid female and worker of 

 this species. 



able 



to bring up a great number of 

 workers, males and females of their own species. Although the 

 Leptotlwra.r may be said to be truly parasitic, they have lost none 

 of their essential instincts, such as those of excavating the nest 

 and rearing their young. Only their feeding habits have become 

 peculiarly modified, without, however, completely supplanting the 

 ability to eat independently. Nevertheless the opulent trophic con- 

 ditions among which the inquilines live have begun to tell on the 



