66 THE HUMBLE-BEE 



in 



a box for observation. Rupestris queens were 

 particularly plentiful that season, and one was 

 first seen in the lapidarius nest when only eight 

 workers had emerged. The next day when I 

 looked into the box this rupestris was out, but on 

 the following day I was surprised to see two 

 rupestris on the comb, apparently living on good 

 terms with the lapidarius queen and her children. 

 After this I inspected the box at least twice every 

 day. On the first few occasions there were some- 

 times two rupestris females, and once three, to be 

 seen in the nest, but after two or three days only 

 one remained, and she was always at home. The 

 poor lapidarius queen was visibly depressed and 

 ill at ease in the dominating presence of the 

 Psithyrus. As time went on she grew nervous 

 and languid, and showed increasing fear and 

 suspicion of the unwelcome guest. Finally, at 

 11.30 a.m. on the tenth day after the first appear- 

 ance of a Psithyrus in the nest, I found the queen 

 and three workers lying dead outside the nest, and 

 the Psithyrus on the comb displaying more activity 

 and satisfaction than usual. Evidently the three 

 workers had sacrificed their lives in a futile attempt 

 to destroy their mother's murderess. The next day 

 the Psithyrus laid some eggs. 



Here we have evidence for supposing that the 

 death of the queen is brought about by the develop- 

 ment of eggs in the Psithyrus causing jealousy 

 and a duel, the two queens, as in the case of 

 rival Bovibus queens, being unable to tolerate one 



