Dec.,i9i6 Bulletin of the Brooklyn Entomological Society 105 



well known to European entomologists, workers referable to it 

 with certainty have never been found. So the suspicion arose 

 that this species has no workers, but breeds as an inquiline in the 

 nest of some other species. This suggestion, first made by Mora- 

 witz (1864), was strongly supported by Schmiedeknecht (1881) 

 and Holmgren (1883). But it was not until 1898 that direct ob- 

 servations, made by Robson, supported the belief of inquiline rela- 

 tionship between V. austriaca and V. rufa. However, by far the 

 most important paper on the subject was published in 1903 by G. 

 H. Carpenter and D. R. Pack-Beresford. These authors not only 

 made a complete comparative study of the two forms, but they 

 attempted also to become more closely acquainted with the exact 

 nature of the relations existing between them. 



In resume, three different opinions may be held as regards the 

 relation existing between V. austriaca and V. rufa. 



1. The older opinion, recently renewed by R. du Buysson, sees 

 in V. austriaca merely a color- variation of F. rufa. The 5 and 

 (^ austriaca have then in the economy of the nest the same stand- 

 ing as the ordinary rufa $ and ^. This can hardly be accepted 

 any longer, as there are many structural characters separating 

 both forms and, furthermore, this does not explain why no 

 workers presenting the structural peculiarities of austriaca are 

 found. 



2. The inquiline theory as presented by Schmiedeknecht, Rob- 

 son and J. Perez (1910) : according to this, V. austriaca is a dis- 

 tinct species, whose $ and -^ play in the V. rufa nest the same 

 role as the Psithyrus $ and J^ in the Bombus nests. The 5 of 

 austriaca invades the nest of a V. rufa, lays its eggs in the cells 

 and the hatching larvae are fed by the rufa workers. 



3. The opinion of G. H. Carpenter and D. R. Pack-Beresford 

 is in some respects intermediate between the two preceding theo- 

 ries. They believe that V. austriaca and V. rufa must have di- 

 verged from a common stock in comparatively recent times. They 

 add further : " The observations that we have been able to make 

 on the nest containing both forms strongly incline us to the view 

 that, although their differences are apparently ' specific,' there is a 

 direct genetic relationship between them and that they may be re- 

 garded as races of one and the same species. . . . We conclude, 



