No. 415.] NESTS OF AMERICAN ANTS. 523 
7. Pheidole carbonaria Pergande, subsp. calens Forel. 
At Aguas Calientes, Mexico, I observed several nests of this 
small, timid Pheidole on the slopes or about the bases of the 
beautiful gravel cones of the typical Pogonomyrmex barbatus, 
and its variety, molifactens. The Pheidole was not found else- 
where in the vicinity, but my stay was too brief to enable me to 
assert that this ant really exhibits a more definite association 
with Pogonomyrmex than that of Forelius and Dorymyrmex. 
From the appearance of its soldiers, Phetdole carbonaria would 
seem to be a seed-storing species like our Texan Pheidole kingi 
André, var. instabilis Emery, and the Northern Pheidole pilifera 
Roger (= pennsylvanica Roger). If this is true, the Mexican 
insect may be a thief-ant feeding on the seed stored by the 
agriculturals in their large chambers, which are often suffi- 
ciently near the surface of the mounds to be invaded by small 
ants. 
8. Formica sanguinea Latr. 
McCook (82, p. 152) found colonies of Formica sanguinea, 
with their slaves, within the clearings of three different nests 
of Pogonomyrmex occidentalis in Colorado. These and several 
other ants appeared to be tolerated in this situation by the 
occident ants. Such observations show that the association of 
ants with the Pogonomyrmex cannot be in all cases prompted 
by a desire for greater protection, since F. sanguinea is a 
bold, predaceous species, quite capable of making its way 
independently. It also shows that the formicary precincts of 
the agricultural ants may be open to some intruders of con- 
Siderable size. Experience has taught me that it is not an 
easy matter to determine the attitude of these ants towards 
other animals. This is evident from the following jottings 
from my notebook : Pogonomyrmex barbatus sometimes permits 
the leaf-cutting ants (Atta fervens) to wear a groove-like path 
diagonally across its disk. It will also allow large tenebrionid 
beetles ( EZeodes tricostatus), often to the number of six or eight, 
to stalk about for hours unmolested on its nest, and to feed on 
the refuse vegetable matter accumulated within the confines of 
