WHEELER— THE PARASITIC ACULEATA. 27 



mecophiles, there remains the interesting problem as to the phylo- 

 genetic relations of the slave-makers, temporary and permanent 

 social parasites. Obviously the permanent parasites can be readily 

 conceived as developing either from temporary parasites or from 

 dulotic species. The fact that there are among the social bees and 

 wasps, as will be shown in the sequel, certain forms which agree in 

 all essential particulars with the permanent social parasites among 

 ants, although for obvious reasons they cannot have arisen from 

 dulotic forms, would seem to point to the origin of the permanent 

 from the temporary type of social parasitism. On the other hand, 

 Polycrgiis seems clearly to be in a stage transitional from dulotic 

 to permanent social parasitism, and a more advanced stage appears 

 to be represented by Strongylognathus testaceus which lives with 

 Tctramorium caspitum and produces workers which are few in 

 number and endowed with very feeble slave-making proclivities. 



It is more difficult to determine the phylogenetic relations of the 

 dulotic to the temporary parasites. Wasmann (1905), Emery 

 (1909), Viehmeyer (1909, 191 1), Brun (191 2) and I have dis- 

 cussed this matter in several papers. Wasmann holds that tem- 

 porary social parasitism, which I first discovered in various North 

 American species of Formica, arose from the pleometrosis of such 

 forms as Formica ritfa. In a single colony of this and other acer- 

 vicolous species the females may be very numerous and new nests 

 may be formed by daughter queens departing from the maternal 

 nest with contingents of workers, or recently fecundated queens 

 may secure adoption in other nests of their own species. At first 

 I was inclined to derive both dulosis and temporary social para- 

 sitism from such conditions, but Wasmann insisted on deriving 

 dulosis from temporary social parasitism, a view which Emery, 

 Viehmeyer, Brun and I have rejected as unsound on the principle 

 that parasitism may readily arise from predatism, but that the re- 

 verse development is biologically highly improbable. I am now 

 inclined to agree with Emery that pleometrosis and the adoption 

 of queen ants by workers of their own species are probably phe- 

 nomena sui generis which did not lead to social parasitism, that we 

 must assume a predatory stage not unlike that of F. sanguinea as 

 the starting point for dulosis and that temporary social parasitism 



