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x OBSERVATIONS ON PS/ITHYRUS 257 
triumphed, as she always does in nature, had not 
something happened to weaken her power and 
increase that of the workers. That something, | 
believe, was my adding workers from the queen- 
less nest. Many of these workers contained eggs, 
and it was over these that the Pszthyrus 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 Pszthyrus 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. 
latrerllellus, a species that is not preyed upon by 
any species of Pszthyrus, I have never seen the 
queen’s eggs molested by the workers. 
On July 20, 1911, I took a nest of B. terrestris 
victimised by 7s. vestalis and transferred it to my 
humble-bee house. There were 49 workers, mostly 
small, 3 vestazzs males that had emerged within 24 
hours, the old ves¢alzs queen, a long-dead ¢errestris 
queen and the remains of another, 67 vesta/zs female 
cocoons, 103 vestafzs male cocoons, and a quantity of 
larve and eggs. One of the egg-cells contained 18 
vestalis eggs. The brood had the same smell as 
that of the ¢evrestrzs brood in my other nests except 
that it was rather stronger; the ¢errestrzs workers 
seemed exceedingly fond of it, and when I brought 
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