204 



THE HUMBLE-BEE 



VIII 



and is very helpful in distinguishing them from one 

 another. 



The coat is less dense than in the Bombus queens, 

 the hair being particularly scanty on the abdomen, 



Ps. rupestns P$- barbutellus 



Ps. vestalis Ps campes tris 





hwlf 



mm 



Ps. disimctus Ps. quodricolor 



Fig. 30. Tip of the abdomen (underside) of the queen of each of the British 

 species of Psitkyrus, showing the elevations on the 6th ventral segment. 



which in the middle looks almost bare ; also the 

 hairs are somewhat coarser than in Bombtts. 



Psitkyrus queens usually have their wings more 

 clouded than Bombus queens, and they may generally 

 be recognised in the field by their weaker flight with 

 its distinctly lower-pitched and softer hum. 



