64 THE HUMBLE-BEE 



in 



of workers has emerged, and this is the most 

 favourable time, for these early workers are less 

 hostile to strange queens than are the workers that 

 emerge later. If the Psithyrus fails to find the nest 

 until the workers have become numerous they set 

 upon her with great fury, and, after some time, gener- 

 ally succeed in killing her by stinging her in a 

 vulnerable spot, as for instance in the neck. On 

 June 20, 1894, I took a nest of B. terrestris in 

 an unusually forward stage for this date, there 

 being 50 workers, 6 males, 2 young queens, and a 

 quantity of male and queen cocoons. In the hole 

 were two dead Psithyrus vestalis females, both 

 perfectly denuded of hair, and 15 dead terrestris 

 workers. Evidently the Psithyri had been killed, 

 but only after severe fighting and heavy loss. Again, 

 on July 14, 191 1, I found the dead body of a Ps. 

 vesta/is, also absolutely hairless, lying in the grass 

 at the mouth of the tunnel of a strong terrestris 

 nest : the workers must have killed her and dragged 

 her to the surface. 



It is, therefore, necessary for the Psithyrus to find 

 the nest before many workers are out, but it would 

 not be to her advantage to kill the queen until the 

 latter has laid the greater number of the worker 

 eggs ; and, as a matter of fact, she does not do so. 



The Bombus queen, on first meeting the 

 Psithyrus in her nest, shows a certain amount 

 of agitation, and may advance to attack her, but, 

 her courage failing, she draws back. The Psithyrus, 

 however, treats the queen with good-natured in- 



