232 



The Irish Naturalist, 



Septembef, 



(figs. A, B). Bombus and Psithyi'us are not very widely 

 separated from each other ; indeed, they are probably more 

 nearly akin than any two genera which stand in the relation- 

 ship of host and guest. Yet the armature in these two bees 

 shows a marked distinction as compared with the slight com- 

 parative differences in our two wasps. Compare the large 

 terminal segment of the stipes and the short falcate sagitta 

 in Psithyriis with the corresponding parts in Bombus. 



A B 



*L«- 



Fig. A. Male armature oi Bombus lapidariiis, Linn. \st. stipes. 

 B. „ „ rsithyriis rupestris, P'ab, ] sa. sagitta. 



After Saunders. Magnified lo times. 



On any view as to their habits, the structure of Vespa rufa 



and V. aitstriaca^ and the fact that each form varies in the 



direction of the other, show that they must have diverged 



from a common stock in comparatively very recent times. 



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 regarded as races of one and the same species. Unless 



something altogether abnormal happened in the development 



of the individuals inhabiting one nest, we are forced to that 



conclusion. For, during the period when the only old queen 



in the nest was an austriaca, there emerged from the cells 



males of both forms, including specimens of 7'uja varying 



tow^ards austriaca, young queens of ausiriaca, and a worker of 



rtifa ; and it is especially noteworthy that the latest wasps to 



emerge, long after the nest was full of aust?daca queens and 



drones, were examples of 7iifa. The ru/a males which 



hatched out might possibl}' have been the offspring, produced 



