5 18 THE AMERICAN NATURALIST. [Vor. XXXV. 
mention, in passing, one very beautiful example. On March 9 
of the current year I found two double nests under large stones 
on opposite sides of a road near Austin, Texas. The ants 
were in both cases the huge black Ponerine Pachycondyla 
harpax and the fine honey-yellow Camponotus fumidus, var. 
Jestinatus (= Formica festinata Buckl). In each case the 
latter species had excavated its nicely finished galleries and 
chambers under the middle of the stone, while the former had 
extended its few broad and irregular burrows along the sur- 
face so as nearly to encircle the Camponotus nest. The con- 
trast between the color of these large ants, the one belonging 
to the most primitive, the other to the most specialized sub- 
family of the Formicide, was scarcely greater than that ex- 
hibited by their architecture. As soon as the nests were 
uncovered the Camponoti sniffed the presence of their black 
neighbors and hastily retreated into their galleries; while the 
Ponerinze seemed as oblivious of their fellow-tenants as the 
occupants of a Chicago apartment building. Similar nests of 
P. harpax and C. maculatus, subsp. sansabeanus, are not infre- 
quent in the neighborhood of Austin, but these, too, are 
merely accidental associations, as all three of the species men- 
tioned are nearly always found occupying single nests. 
The second class of plesiobiotic colonies, viz., those which 
have been considered by some authors as incipiently symbiotic, 
really represent very little advance on cases like those above 
described. I am convinced that the supposed regularity of 
these associations may be largely the result of hasty or inade- 
quate observation. In several instances the two species of 
ants are quite as often, or even more frequently, found in 
single nests. Usually one of the species is of diminutive size, 
and this has led observers to suppose that they were dealing 
with a small and feeble ant living under the wing of a formi- 
dable neighbor. It is, however, quite as probable that the two 
species occur together, because both affect the same natural 
conditions, such as soil, moisture, presence or absence of vege- 
tation, etc. This is noticeably the case with Pogonomyrmex 
and its various satellites, 
