60 THE, HUMBLE-BEE 11 
upon the bounty of the Lomd:z. This view was 
upheld by Hoffer, who, in 1889, published a mono- 
graph on the Psz¢hyrz' in which he recorded ob- 
servations of his own in Styria supporting it. But 
my observations have shown that at least two of 
the species of Pszthyrus are deadly parasites upon 
the species of Bombus in whose nests they breed. 
In the years 1891 to 1894 I dug up many nests 
of Lombus Jlapidartus containing its parasite 
Psithyrus rupestris, and of B. terrestris containing 
its parasite Ps, ves¢talis, and I noticed that in every 
case the Pszthyrus female had taken the place of 
the mother of the colony, whose remains I gener- 
ally found lying under or near the nest. Investiga- 
tion showed that it is the practice of the Pszthyrus 
female to enter the nest of the Bomdbus, to sting 
the queen to death, and then to get the poor workers 
to rear her young instead of their own brothers 
and sisters.” 
The way in which the Pszthyrus queen proceeds 
in order to ensure the success of her atrocious work 
has all the appearance of a cunning plan, cleverly 
conceived and carried out by one who not only is 
a mistress of the crime of murder, but also knows 
how to commit it at the most advantageous time 
for herself and her future children, compelling the 
1 Die Schmarotzerhummeln Steiermarks, by E. Hoffer (Graz. Nat. Ver.), 
oe outline of the life-history of Psz¢hyrus here described was given in my 
privately published booklet Zhe Humble-bee, its Life-History and How to 
Domesticate It, in 1892. See also Amateur Naturalist, Croydon, of May 
1893, p. 38 ; and Hymenoptera Aculeata of the British Islands, by E. Saunders, 
1896, p. 354- 
