92 Bulletin American Museum of Naturayjiistory. [Vol. XXII, 



vicissitudes to which they are subjected during their development. 

 This is especially true of parasitic animals like the Cestodes, Meloid 

 beetles, etc. Similarly in ants, the larger the females the smaller the 

 number of them produced by a single colony, and the fewer the 

 vicissitudes they must encounter in founding their colonies. The 

 analogy holds good also in respect of parasitic species like F. 

 consocians. 



It is, I believe, admissible, as I have asserted in a former paper, to 

 extend the conclusions derived from a study of F. consocians to sev- 

 eral other species of Formica belonging to the rufa group and having 

 similarly diminutive or otherwise aberrant females. The species of 

 Formica which I have described under the names of microgyna, mon- 

 tigena, nevadensis, impexa, and nepticula all have diminutive females, 

 and small colonies of the two first mixed with F. suhsericea workers 

 have been actually observed. The females of F. areas, ciliata, dakotensis 

 and its var. wasmanni are aberrant in coloration and, though larger than 

 the females above mentioned, are nevertheless smaller than those of the 

 jusca and pallide-fulva groups. The very long yellow hairs of the fe- 

 male ciliata are especially remarkable and indicate that this insect must 

 be a genuine inquiline. Mixed colonies of wasmanni with suhsericea 

 have been observed by Muckermann. Even exsectoides and the vari- 

 ous varieties and subspecies of rufa, which have larger queens than 

 the preceding species, are in all probability temporary social parasites. 

 Several young colonies of exsectoides mixed with suhsericea have been 

 observed, and Wasmann has found, as I predicted, that the European 

 F. truncicola presents essentially the same conditions as consocians. 

 The behavior of F. integra, as shown in the above experiments, is 

 clearly suggestive of inquilinism. I have also added a Myrmicine ant, 

 Stenamma (Aphcsnogaster) tennesseense to this series of forms, since 

 there is evidence that its diminutive, very glabrous and bright red 

 females start their colonies with the aid of workers of 5. {A.) fulviim 

 or some one of its varieties. 



Questions concerning the phylogenetic origin of parasitic habits are 

 notoriously difficult to answer. The obstacles to an explanation of cer- 

 tain cases of social parasitism, however, like those seen in F. consocians , 

 truncicola, etc., seem to have less weight than in the case of ordinary, 

 or nonsocial parasitism. From the very nature of social organization 

 in ants, the female may be regarded, throughout a large portion of her 

 life, as a parasite on the workers of her own species. As a virgin she is 

 a parasite on the maternal colony, as a mother, on her own offspring ; 

 so that both by instinct and tradition she has a pronounced proclivity 



