mes) 7 ioe s LE USURPER-BEE’ 61 
poor orphans she creates to become her willing 
slaves. 
The following are the details of the life-history 
of Pstthyrus rupestris and Ps. vestalis as | have 
observed them :— 
The queens hibernate solitarily in the ground 
like the Boméus queens, but they do not quit their 
winter quarters until after the Bomdbus queens have 
emerged, and most of them are already engaged in 
rearing their first batch of workers. 
Psithyrius rupestris much resembles her victim, 
the /aprdartus queen, in appearance, being about 
the same size, and, like her, having a black coat 
with a red tail; but her wings are dark brown, not 
clearly transparent as in /afzdarius, and her flight 
is feeble, producing a lower note than that of the 
lapidartus queen, the rate of wing vibration being 
slower. Ps. vestalis also rather resembles her 
victim, B. ¢errestrzs, in her yellow band and whitish 
tail, but is likewise distinguishable by her smoky 
wings and soft low-sounding flight. 
But the most remarkable feature about the 
Psithyrus queens is their exceedingly thick and 
hard skin, covering them like a coat of mail and 
protecting them from the stings of the Bomdz. The 
segments of the abdomen, in particular, are very 
hard and lap tightly and closely over one another, 
there being no wax-yielding membrane between 
the dorsal segments, so that it is very difficult for 
an adversary to force her sting between them. 
Their coats are thin, perhaps as a compensation 
