No. 432.] FORMICA CINEREA MAYR. 949 
occurs most commonly, however, in such peculiar situations 
that there is little difficulty in understanding why it has been 
so long overlooked. The formicaries are so large and populous 
that it can hardly be regarded as an imported species unless 
it resembles some of the European weeds which have found 
the American soil so very favorable to their growth and 
expansion, 
The following account of the localities in which I have taken 
F. cinerea, together with some notes on the structure of its 
formicaries, may prove to be of interest to students of insect 
distribution in general and of our American Formicida in par- 
ticular. There are three of these localities some ten miles 
apart, in different directions and at least three to five miles 
from the town of Rockford, and in each of these localities, 
which are. all open and exposed to the full heat of the sun, the 
nests are of a different type. August 20, I found a single 
nest, the first I had seen, under a small log in a meadow. 
This nest was not very populous and contained neither larvae 
nor pupa. It consisted of several inosculating galleries of the 
type usually made by species of Formica and extended down at 
least to a distance of 20 cm. into the black, waxy soil. The ants 
were timid, like the inhabitants of all small nests of Formica, 
and made no attempt to attack me. August 22, I found two 
very large nests side by side at the edge of a turnpike not far 
from a meadow. Each of these covered an area of somewhat 
more than a square meter, and each consisted of a flat mound 
of earth about 10 cm. high, strewn with little straws and sticks 
brought together by the ants. This débris concealed numerous 
openings from which the ants rushed forth as soon as the nest 
was disturbed. Excavation was difficult on account of the 
hardness of the soil, but it was easy to make out that the 
formicary consisted of a honeycomb of galleries 1-2 cm. in 
diameter and extended down into the soil to a depth of more 
than 30 cm. It was filled with worker larve and pupæ, 
together with thousands of ants, which attacked me furiously, 
using their jaws and formic acid batteries to good purpose. 
August 25, I discovered a locality where there are hundreds of 
cinerea nests. This is a meadow about a mile and a half long 
