x OBSERVATIONS ON PSITHYRUS 257 



triumphed, as she always does in nature, had not 

 something happened to weaken her power and 

 increase that of the workers. That something, I 

 believe, was my adding workers from the queen- 

 less nest. Many of these workers contained eggs, 

 and it was over these that the Psithyrus had been 

 unable to maintain her authority. 



I think that the strange race-suicidal habit the 

 lapidarius workers have of attempting to devour 

 their mother's new-laid eggs is associated with the 

 parasitism of Psithyrus. It is natural to suppose 

 that workers that attempt to devour the eggs of 

 their Psithyrus step-mother perpetuate their egg- 

 devouring instinct through their sons that they 

 sometimes succeed in rearing. In support of this 

 view it is interesting to note that in nests of B. 

 latreillellus, a species that is not preyed upon by 

 any species of Psithyrus, I have never seen the 

 queen's eggs molested by the workers. 



On July 20, 191 1, I took a nest of B. terrestris 

 victimised by Ps. vestalis and transferred it to my 

 humble-bee house. There were 49 workers, mostly 

 small, 3 vestalis males that had emerged within 24 

 hours, the old vestalis queen, a long-dead terrestris 

 queen and the remains of another, 67 vestalis female 

 cocoons, 103 vestalis male cocoons, and a quantity of 

 larvae and eggs. One of the egg-cells contained 18 

 vestalis eggs. The brood had the same smell as 

 that of the terrestris brood in my other nests except 

 that it was rather stronger ; the terrestris workers 

 seemed exceedingly fond of it, and when I brought 



