1922] Unique Method of Defense of Bremus fervidus Fabricius 181 



colony No. 7 {B. fervidus) the preceeding evening, was found 

 sitting near the entrance of her nest and, like the Psithyrus 

 queen, was completely covered with a sticky liquid. Whenever 

 this worker attempted to enter the nest, she was immediately 

 attacked by her sisters and driven back. The reason for this 

 strange behavior and the source of the sticky liquid, which the 

 writer at first was unable to account for, were disclosed several 

 days later. 



On July 27th a captured Psithyrus laboriosus queen was 

 placed in a Bremus fervidus nest and the writer was surprised to 

 find that the workers, instead of creating a furore and killing the 

 Psithyrus, as do the workers of Bremus impatiens, remained 

 calm and resorted to a more peaceful, but equally effective, 

 method of expelling the intruder. About a dozen workers 

 gathered about the Psithyrus queen, and, after stealthily 

 approaching a little closer, each one placed a small drop of 

 liquid on the intruder with her mouth. The Psithyrus queen 

 did not seem to relish this performance and slowly left the comb, 

 apparently seeking to hide herself. A number of workers followed 

 her and from time to time added more liquid until she was as 

 wet as the Psithyrus queen and Bremus worker referred to above. 

 The experiment was repeated with other fervidus colonies and 

 was later (September 13th) demonstrated before the Cambridge 

 Entomological Club. The members of the club were also shown 

 the. very different behavior of a Bremus impatiens colony under 

 these conditions. 



J'rom July 27th to September 24th a large number of other 

 experiments were carried out in order to determine how colonies 

 of Bremus fervidus react to other intruders. These experiments 

 may be summed up briefly as follow"s: 



Experiment 1. Introduced: Young queen of Psithyrus 

 ashtoni Cresson. 



Result: Daubed with liquid like Psithyrus laboriosus. No 

 attempts to sting her. 



Experiments 2, 3, 4 o,nd 5. Introduced (separately) : 



