72 THE HUMBLE-BEE 



in 



prey on the Bombi. It is a remarkable fact that 

 the sting of the terrestris queen differs from that 

 of the lucorum queen and approaches that of 

 Psithyrus in being somewhat stouter and more 

 curved, and having its thickened basal portion more 

 parallel-sided when viewed sideways than in lucorum. 

 There is, however, no evidence to show that any 

 species of Psithyrus has sprung from the particular 

 species of Bombus on which it preys, such resem- 

 blances as it may show to it in coat-colour, etc., 

 being pretty clearly attributable to mimicry or 

 exposure to the same conditions of life, and not to 

 ancestry. 



The males of the Psithyri are very fond of 

 drowsing on flowers, especially on the heads of the 

 knap-weed ; they are even more fragrant than the 

 males of the Bombi. In their play, which is probably 

 amorous, they hover over meadows and grassy 

 slopes. I know two exposed grassy inclines, both 

 facing north-west and having no trees near, where, 

 every August, the males of Ps. rupestris may be 

 seen flying about, skimming the grass, sometimes in 

 considerable numbers. I have seen the males of 

 Ps. barbutellus hovering over the grass in the same 

 way in July, but in the vicinity of trees. 



I have dug up the hibernating queens of Ps. 

 rupestris, vesta/is, barbutellus, and campestris from 

 banks facing north-west, occupying little cavities in 

 the ground, about two inches below the surface, 

 exactly like the queens of B. lapidarius and other 

 Bombi. 



