THE DEGENERATE SLAVE-MAKERS. 491 



forays on alien colonies of Tetramorium. When the latter are brought 

 near a mixed colony and a conflict ensues, the testaceus endeavor to 

 kill the strange workers, but are too feeble to pierce their armor, 

 and, if the mixed colony is victorious, this is due to the efforts 

 of the host workers. The tcstaceus, though able to excavate and 

 to feed independently, contribute little or nothing to the structure 

 of the nest and probably obtain most of their food from the tongues 

 of the Tetramorium. The broods of both species are cared for by the 

 host, since the parasites have ceased to interest themselves in the educa- 

 tion of their own young. Unlike many parasitic ants, S. testaceus is 

 often found in vigorous and populous colonies of the host species. The 

 flourishing condition of such colonies, a number of which were shown 

 me by Air. Viehmeyer in the heaths near Dresden, must be due either 

 to the retention of the Tetrainorium queen or to the adoption of the 

 Strongylognathus queen at a very late stage in the development of the 

 colony. That we must accept the former alternative is proved by the 

 following observations : In Bohemia, Wasmann found a large mixed 

 colony which contained 15,000-20,000 Tetramorium, some thousand 

 Strongylognathus and pupae of both species. About 70 per cent, of 

 the pupae were males and females of the parasitic species, the remainder 

 were worker pupae, and there were two large male pupae of the host. 

 This nest contained a fertile queen of Tetrainorium and one of Strongy- 

 lognathus, living side by side. During June, 1907, Professor Forel and 

 I were able to confirm this discovery. We found a similar testaceus- 

 Strongylognathus colony on the Petit Saleve, near Geneva. This colony, 

 though much smaller than the one described by Wasmann, contained a 

 fertile Tetramorium queen. The diminutive Strongylognathus queen 

 was not found, but must have been present, as there were in the nest 

 young worker pupae in addition to the imagines of this species. Was- 

 mann is inclined to believe that these mixed colonies arise through the 

 alliance of a testaceus and a Tetramorium queen, but it is more probable 

 that the former enters a colony of the latter after it has been estab- 

 lished and become rather populous, since the founding of colonies even 

 by pairs of queens of the same species is an extremely rare occurrence 

 (see p. 190). Although the host and parasitic queens come to live side 

 by side in the mixed colonies, the offspring of the latter are exclusively 

 workers, the two male pupae found by Wasmann being the only known 

 exception to this rule. Forel (ipoorf) explains this absence of the male 

 and female offspring of the host queen as the result of a regulatory 

 instinct : " The females and males of Strongylognathus are smaller and 

 less troublesome to nourish. This is evidently sufficient to induce the 

 Tetramorium workers to rear them in the place of their own enormous 



