794 THE AMERICAN NATURALIST. [VoL. XXXV. 
number of its workers by importing and employing foreign labor. 
This may result naturally from the fact that in weak colonies 
on an average a larger percentage of the stolen pupæ are per- 
mitted to develop into slaves. In populous sanguinea colonies, 
on the other hand, a considerable portion of the prey is de- 
voured even when thereis plenty of other insect food within 
reach. ; 
The relations implied by the terms “slave” and * master" 
do not adequately express the conditions existing in these 
mixed nests, since sanguinea works side by side with its auxil- 
iaries, which are neither a mere luxury nor an absolute neces- 
sity. Still, although sanguinea is capable of excavating and 
maintaining its own nest, the auxiliaries appear to be more 
enthusiastic and skillful workers in the earth. And although 
sanguinea looks after its own brood and the hatching of the 
cocoons of the auxiliary species, it must, nevertheless, derive 
some advantage from the assistance of its slaves. The latter, 
moreover, bring into the nest a good deal of food from the 
aphides, which they assiduously attend. 
F. sanguinea, on moving to a new nest, usually carries its 
slaves, and is rarely carried by them. This is probably due to 
the fact that the sanguinea are of a more excitable tempera- 
ment and therefore have a greater tendency to take the initia- 
tive in a change of dwelling than their more stolid auxiliaries. 
Continental authorities uniformly maintain that the n 
guinea-fusca nests contain only workers of the auxiliary species. 
In England, however, Rev. T. D. Morice (00, p. 98) recently 
found a nest which contained also fusca males and queens in 
addition to the workers of this species. This very exceptional 
condition would seem to have arisen either from the failure of 
the sanguinea to consume all the pupz of the fertile sexes of 
fusca, or less probably from the formation of an alliance colony 
between fertile queens of sanguinea and fusca. 
Polyergus rufescens Latr. — The * amazon," as the paragon 
of dulotic ants, has been observed with great care by à num 
ber of investigators, among whom Pierre Huber (10) and Forel 
(74) hold the first place, It is a rather large, brown-red ant, 
allied to Formica, but characterized by the possession of slender, 
