Pee a7 nc.5, bite USURPER-BEE 63 
she had lost the scent she returned at once to search 
again inside. 
The Psithyrus is much more likely to find a 
nest if the tunnel leading to it is short than if it 
is long. Most of the nests containing Pszthyri 
that I have dug up had tunnels not exceeding 
fifteen inches in length, and in none were they over 
two feet. It is probably to escape the Pszthyrus 
that /apzdarius and terrestris nests often have 
longer tunnels than those of any other species. 
In her wanderings the Pszthyrus may find and 
enter the nest of some other species of Bomdbus. 
Having succeeded in making herself acceptable to 
the inhabitants, she becomes a temporary lodger 
in this nest, making it her headquarters and re- 
turning to it for meals and also to pass the night. 
I once found a Ps. rupestris queen lodging in a weak 
nest of &. agrorum in the thatch of a cow-lodge ; 
another rupesty7s was a frequent visitor in a nest 
of B. derhamellus | had under observation in June 
1910, where she was supported by the queen only, 
no workers having yet emerged. I found a Ps. 
vestalis lodging with a LB. derhamellus queen on 
June 9, 1910. On June 10, I found a Ps. vestals 
in a nest of B. pratorum with the queen and 
seven workers; and on July 4, I discovered a Ps. 
vestalis in a nest of B. pratorum containing the 
queen and twenty workers. I have never found 
a Psithyrus lodging in a populous nest. 
The majority of the Pszthyrus queens discover 
the nests of their victims when only the first batch 
