i PERPE-BISTORY OF ZOULCS 57 
clusion that the original queen tolerates the intruder 
only so long as the latter has no eggs to lay, the 
two mothers being unable to endure one another's 
presence. 
Each queen that attaches herself to the nest of 
another means one less colony started, and it is 
hard to see of what advantage this habit can be to 
the species except the survival of the best fighters. 
One would suppose that the attachment of one or 
more queens to a nest might be a safeguard against 
the perishing of the young, should their mother get 
lost, but my observations show that the satellite is 
not sufficiently settled in life to assume the care of 
the brood until she is about to lay eggs. It is, in 
fact, the imminence of motherhood that makes her 
look after the brood, although success in a duel 
rouses her to do so. 
I have discovered one very interesting exception 
to the rule that only the queens of the same species 
prey upon one another. 
On June 15, 1894, I found a nest containing a 
terrestris queen with ten workers, all of which were 
of the closely allied species /ucorum, and a dead 
lucorum queen, evidently the mother of the workers. 
On the same day | found another nest containing 
about twenty workers, all Zucorum, with a terrestris 
queen and the decaying remains of two ducorum 
queens. These, and several similar cases met with 
in later years, leave no doubt that the ¢errestras 
queens frequently enter the Zwcorwm nests, kill the 
lucorum queens, and get the Zucorum workers to 
