170 
Psyche 
[September 
( Spirea alba Du Roi) and some not very flourishing berries: red 
raspberry ( Rubus idaeus L.), creeping blackberry ( Rubus fiagellaris 
Willd.) and common blackberry ( Rubus sp.). Just back of the nest 
more vigorous Spirea alba made an almost complete wood-field 
fringe and extended back into the wood for 6 to 14 feet, forming 
a shrub layer until the more moist ground near the swamp was 
taken over by a thick growth of sensitive fern ( Onoclea sensibilis L.). 
The visible parts of the nest consisted of a series of inconspicuous 
low grass-thatch mounds strung along parallel to the woods edge 
behind and to the road in front. In 1969 there had been seven major 
mounds along 30 feet, but in 1970 those of the northeast half of 
the line had been abandoned and the ants occupied 10 mounds along 
the south-west 15 feet. A main cluster, lying near the center of the 
line, was composed of five, which rose into peaks of three to six 
inches and intercommunicated by low thatch structures barely above 
ground level. This made a conglomerate which stretched out into 
a very irregular shape, which was four feet at its longest extension. 
The five other mounds had no above-ground thatch connections. 
Three of these extended to the north-east of the main group and 
were 16, 33 and 38 inches from it. A fourth was 9 feet to the 
south-west and the last was five feet back from the main group and 
lay at the base of a poplar tree at woods edge. The mounds varied 
in diameter from 8 X 10 inches to 18 X 21 inches and in height 
from two to six inches. 
Structure of the mounds. The mounds were built of grass 
thatch with bits of poplar and spirea leaves intermingled. Live 
grasses growing through them gave some reinforcement but major 
support was furnished by spirea and berry stems. Superficially they 
looked much like enlarged igloo mounds of Dolichoderus mariae 
but inside there was no large central chamber. Instead, the grasses 
formed floor and ceiling for two or three stories of chambers and 
galleries. These provided a surprisingly dry place for pupae to 
mature. Concealed runways at the bottom of the mounds extended 
out just under the compressed leaf layer and were cut into the 
ground for about one-fourth of an inch. They ran to other mounds 
and to foraging areas. In addition there were galleries and chambers 
cut beneath the ground surface down among the plant roots for 
three or more inches. Thus part of the nest was underground and 
the mounds served primarily for hastening the maturing of brood. 
The mound set back at the base of the poplar tree at woods edge 
had a special significance. It was large, 20 X 21 inches across, and 
was built up partly of soil. On September 24, 1971, considerable 
