1934 ] 
Three New North American Ants 
199 
small sage brush plant around the stem and lower branches 
of which the rather flat mound had been constructed. On 
the surface of the mound were numerous clusters of ants. 
Examination showed that these consisted of two or three 
microgyna workers industriously engaged in dragging away 
a worker of puberula. In no case did I see any dead raiders. 
Nevertheless the activities of the microgyna workers were 
effective if not lethal for, when their nest was opened, not a 
single raider was found inside. 
Several interesting deductions may be drawn from the 
above data. In the first place it seems obvious that the 
rasilis workers present in the original puberula colony were 
obtained as the result of some unusual condition which en- 
abled the raiders to enter a nest from which they would 
have ordinarily been excluded. In the second place we may 
safely conclude that the infrequent occurrence of members 
of the microgyna group in the nests of slavemakers is due 
to the defensive activities of the former and not to any dis- 
crimination on the part of the slave makers. This is en- 
tirely in keeping with the idea advanced by Dr. W. M. 
Wheeler (5) that the type of slaves which appear in the nests 
of dulotic species will be determined by the abundance and 
degree of docility of the enslaved species. 
(2) The nest founding of Formica ulkei Emery. 
While collecting in the Black Hills of South Dakota in 
September 1933 the author secured numerous specimens of 
F. ulkei Emery in the type locality, Hill City. Among these 
was a single female which had been adopted by a small 
colony of Formica fusca. It may be recalled that in his mon- 
ograph of the genus Formica Dr. Wheeler postulated fusca 
as the temporary host of ulkei (6). The nest in which the 
female just mentioned was taken was a small one consisting 
of not more than three dozen fusca workers most of which 
were minims. It seems likely, therefore, that the nest-found- 
ing activities of ulkei differ in no essential respects from 
those of exsectoides, the female securing adoption by a de- 
pauperate queenless colony of the host species. It may be 
