NOTES ON PSITHYRUS. 



35 



However, as will be seen from the following incident, a battle 

 between a Ps. laboriosus queen and B. impaticns workers may have 

 quite a different ending under somewhat different conditions. On 

 July 24, 19 workers of colony No. 8 (B. impaticns}, which had 

 been transferred to one of the Bussey buildings on the preceding 

 day, were caught at the old nest site and placed in a small glass 

 jar. A few minutes later a Ps. laboriosus queen was discovered 

 on some comb which had been left in the empty nest cavity of 

 colony No. 9 (B. fcrvidus). Just to see what would happen, the 

 Psithyrus was also placed in the jar. All of the inmates, including 

 the Psithyrus, were ill at ease and tried to escape, but one or two 

 of the impaticns workers nevertheless attacked the PsitJiynis queen 

 as soon as they came in contact with her. The latter now went on 

 the warpath herself. She quickly seized one impaticns worker 

 after another, whether attacked by them or not, rolled them below 

 her abdomen and stung them to death. This done, she seemed to 

 feel quite at home in the jar and began to lap up the honey which 

 was oozing out from the bodies of her victims. From what has 

 been said before, it is evident that this encounter would have ended 

 quite differently if it had taken place in the nest of the impaticns 

 workers. This, as well as some of his own observations (e.g., '12, 

 p. 277), disproves Sladen's ('12, p. 253) claim, already referred 

 to, that the B. lapidarius workers, which were mauled by a Ps. 

 rupestris, did not get. hurt because they were too small. 



During the summer of 1905 Wagner ('07, pp. 77, 78) discovered 

 several nests of Bremus muse o rum Linnseus at some distance above 

 ground, and concluded that the nest-building instinct of this species, 

 which normally builds on the ground, is in a process of transforma- 

 tion. The cause for this change he ascribes to natural selection 

 brought about by the fact that the colonies of this species are 

 destroyed, in large number, by various species of PsitJiynis. It is 

 improbable, however, that we are here dealing with a change in 

 instinct. Hoffer ('88, p. 95) records that in the spring of 1886 



Bremus queens, both of which he found uninjured. However, judging from 

 the non-aggressive attitude of the queens, and the belligerent behavior of the 

 workers of Bremus impatiens, the writer would suggest that the two Psithyrus 

 queens were stung to death by the Bremus workers, which, according to 

 Prison, were present in both nests. 



