PSYCHE 
VOL. XXXII. APRIL 1925 
No. 2 
GROWTH OF ANT MOUNDS. 
By E. A. Andrews. 
Johns Hopkins University. 
It is well known that many sorts of ants dig into the ground 
and carrying out mouthfuls of earth soon make conspicuous ant 
hills above their subterranean dwellings. In some, these mounds 
are of considerable size and of long duration and serve as nests 
or places for rearing the young. 
The best known mound builder in America is the rather large 
red and black Formica exsectoides, the mound builder of the Alle- 
ghanies, whose mounds are seen here and there in Nova Scotia, 
Ontario, Maine, New Hampshire, Massachusetts, Connecticut, 
New York, New Jersey, Pennsylvania, Maryland, North Caro- 
lina, Georgia, Wisconsin, Illinois, and Colorado. As one of these 
mounds may contain more than a ton of earth it becomes of 
interest to find out how long the ants must labor to accumulate 
so relatively vast masses of material. One of these ants, alive, 
weighed 10 milligrams. 
When the Rev. H. McCook in 1876 studied the “ant city” 
of local fame near Holidaysburg in Pennsylvania where this ant, 
which he called the wood or fallow ant (locally called pismires) 
had built up as many as 1700 mounds, he soon decided, from the 
occurrence of the very largest mounds on old charcoal hearths, 
that even the mounds that might contain 300 cu. ft. of earth 
were not of any very great age. He also recorded that a field 
plowed in September 1875 showed new mounds in February 1877; 
one ten inches high and 35 in diameter; a second 14 by 48. As 
the work of the ants stops in November these mounds were 
made, he thinks, in a little over one season of work. Again in a 
corn field in July 1876 were two new mounds, each made in two 
months, or one third of a working year, and each measured 8 
inches in height and 18 in diameter. The first hill was, he 
