l62 HYMENOPTERA 



obtaining possession of it ; the legitimate owners disappear, leav- 

 ing the Tomognathus in possession of their larvae and pupae ; 

 these complete their development only to find themselves the 

 slaves of Tomognathus. The subsequent relations of the two 

 ants are friendly, the slaves even preventing their masters from 

 wandering from the nest when they wish to do so. If an estab- 

 lished mixed community of this nature is in want of additional 

 servitors, the Tomogncdlius secure a supply by raids after the 

 fashion of the Amazon-ant, bringing back to their abode larvae 

 and pupae of Leptotlwrax to be developed as slaves. It was for- 

 merly supposed that the Tomognathus continued its species by 

 perpetual parthenogenesis of the workers, for neither males nor 

 females could be found. Adlerz l has, however, now discovered the 

 sexual individuals. The male is an ordinary winged ant, and is 

 so like that sex of the Leptothorax, that Adlerz had failed to 

 distinguish the two before he reared them. The females are 

 apterous, and in fact like the workers. It would perhaps be 

 more correct to say that the workers of this species vary greatly 

 but never become winged ; some of them have ocelli and a struc- 

 ture of the thorax more or less similar to that of winged females, 

 though none have been found with wings. Certain of these 

 females possess a receptaculum seminis, and Adlerz treats this as 

 the true distinction between female and worker. In accordance 

 with this view the female of Tomognathus may be described as a 

 worker -like individual possessing a receptaculum seminis, and 

 having more or less of the external structures of winged females, 

 though never being actually winged. It is probable that other 

 workers reproduce parthenogenetically. The males of this species 

 will not unite with females from the same nest, thus differing 

 from many other ants, in which union between individuals of the 

 same nest is the rule. Finally, to complete this curious history, 

 we should remark that the larvae of the Tomognathus are so 

 similar to those of the Leptothorax that Adlerz is quite unable to 

 distinguish the two. 



Strongylognathus testaceus and S. huberi live in association with 

 Tetramorium caespitum, and are cared for by these latter ants ; it 

 is notable that as in the case of the slave-making Polyergus 

 rufescens the mandibles of the Strongylognathus are cylindrical 

 and pointed, and therefore unsuitable for industrial occupations. 

 1 Bih. Svenska Ak. xxi. 1896, Afd. iv. No. 4. 



