66 THE HUMBLE-BEE MI 
a box for observation. Aupestris queens were 
particularly plentiful that season, and one was 
first seen in the /afzdarius nest when only eight 
workers had emerged. The next day when I 
looked into the box this rapestris was out, but on 
the following day I was surprised to see two 
vrupestrts on the comb, apparently living on good 
terms with the /apzdarius 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 vupestris 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 /apidarius 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 Pszthyrus in the nest, I found the queen 
and three workers lying dead outside the nest, and 
the Psz¢thyrus 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 Pszthyrus 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 Pszthyrus causing jealousy 
and a duel, the two queens, as in the case of 
rival Bomdbus queens, being unable to tolerate one 
