meas ha vROUS, THE USURPER-BEE 67 
another’s presence when they have eggs to lay. 
Whether the jealousy is mutual, whether the 
Psithyrus is the aggressor, or whether the Bomdus 
queen compasses her own destruction by first 
attacking the Pszthyrus, itis impossible to say. In 
the above case, only three hours before I discovered 
that the death of the queen had occurred, I looked 
into the nest and saw both queens on the comb, and 
there was nothing in their behaviour towards one 
another to indicate the approaching tragedy. On 
the whole, I think it probable that the Bomdéus queen 
starts the fight as soon as she discovers that the 
Psithyrus is about to lay, an unpardonable fault in a 
member of her household at this early stage. 
I believe that a Pszthyrus queen never commences 
laying as soon as she enters the nest of her host, and 
that egg-production is the result of living in luxury 
in the nest for some days. Indeed, there is every 
reason to suppose that if the colony when discovered 
by the Pszthyrus is in too early a stage, or too 
struggling a condition, the development of eggs 
in the Pszthyrus, and, consequently, the murder of 
the Loméus, are delayed until the requisite degree 
of prosperity is reached. 
The poor Sombus queen appears to have no 
chance of victory over the well-armed Pszthyrus. 
I have taken a great many nests of /apzdarzus and 
terrestris in all stages, but have seen no evidence 
to show that the Bomdbus queen ever succeeds in kill- 
ing the Pszthyrus, or that she ever escapes being 
destroyed by the latter. Here, however, my 
