o THE HUMBLE-BEE 



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produced, although in a nest containing Ps. vestalis 

 I have seen the terrestris workers lay their eggs. 

 In this same nest, however, I saw the Psithyrus 

 queen calmly eating the workers' eggs, and I think 

 that this is probably the way in which she always 

 disposes of them. 



The Psithyrus queen pays close attention to her 

 new-laid eggs for several hours, giving the workers 

 no chance to molest them, but the workers soon get 

 reconciled to them, and henceforth they feed and 

 tend the Psithyrus brood with as much devotion as 

 if it were of their own species : indeed, they seem 

 sometimes to show a greater fondness for it. H offer 

 found that the larvae of Psithyrus campestris died 

 in a case where the Psithyrus queen disappeared 

 while they were still very young, and concluded 

 that the Psithyrus contributes something essential 

 to the nourishment of her larvae when they are 

 young. I have seen a queen of Ps. distinctus, a 

 species closely allied to Ps. vestalis, feeding her 

 young larvae ; but some later larvae of this queen 

 developed into fair-sized queens, although I removed 

 her when they were very small, namely, twenty-five 

 days before the queens emerged. 



The hard, convex, narrow and naked underside 

 of the abdomen of the Psithyrus queen is unsuited 

 for incubating, and I have never seen her spreading 

 herself over the brood. 



On July 14, 191 1, I took a nest of B. hortorum 

 containing its parasite Psithyrus barbutellus. There 

 were 49 hortorum workers, many with shiny 



