462 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



psychic development. The frequent appearance of a wingless female 

 form, so-called ergatoid queens (fig. 8a), points, furthermore, toward 

 the beginning of inbreeding, although the normal female form is still 

 always more numerous than the ergatoid. 



With the genus Polyergus the development of dulosis within the 

 subfamily of Camponotinse is concluded. Let us therefore now turn 

 to the Myrmicinse. An entirely isolated position is occupied by the 

 European and North American genus Harpagoxenus (Tomognathus). 

 Very likely it is to be phylogenetically derived from the genus of its 

 auxiliary ant Leptothorax; the males are hardly distinguished from 

 those of the latter. The European Harpagoxenus suhlsevis (fig. 9a), 

 which formerly was considered to be a strictly boreal form, has also 

 been found in Saxony by Viehmeyer; he also there discovered winged, 

 normal females, besides the already known ergatoid female form (fig. 

 9a), which appears to be the only one in Scandinavia. Probably 

 Harpagoxenus originally arose through a mutation of female forms 

 in a parent species belonging to Leptothorax. This does not exclude 

 the possibility that it later may have lived in compound nests 

 together with its present-day auxiliary ant (Wasmann and Vieh- 

 meyer), before it arrived at dulosis. 



Another line of development of the slavery instinct among the 

 myrmicines is formed by the genus Strongylognathus, which probably 

 must be derived from the genus of its auxiliary ant Tetramorium. 

 The southern species of this Mediterranean genus are still powerful 

 and populous slave raiders, which are able to procure the pupae of 

 the species of their auxiliaries (Tetramorium ccBspitum) by force. The 

 northern species, Strongylognathus testaceus (fig. 10), which occurs in 

 middle Europe as far as Holland, has, on the contrary, passed over 

 to permanent social parasitism in that its colonies harbor, besides 

 the workers, also a female of Tetramorium, which is furnished them 

 by the new auxiliaries. The workers of Strongylognathus testaceus 

 no longer undertake slave raids; they are likewise too small and too 

 few in numbers for this purpose. Probably it was the northern cli- 

 matic conditions which in this case externally caused the change 

 from dulosis to permanent social parasitism; for when a southern 

 slave-capturing ant penetrates northward, its slave raids, the execu- 

 tion of which is restricted to a certain optimum temperature, become 

 constantly rarer and finally cease altogether. In Strongylognathus 

 testaceus, in connection herewith, the size and the number of worker 

 individuals, have also sunk considerably, all indications of a parasitic 

 degeneration of the species. The sabre-shaped jaws of this small 

 ant are, as it were, no longer more than phylogenetic mementoes of 

 its brilliant dulotic past. The previous history of the genus Strongy- 

 lognathus up to that stage where the southern slave-making species 

 still stand to-day, is just as problematical as the future further devel- 



