Nature Bulletin No. 17  June 2, 1945
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Superintendent of Conservation

****:ANT SANCTUARY

Cook County has an Ant Sanctuary! Out in the Palos, adjoining the 
forest preserve south of Sag Village, is a tract purchased a few years 
ago by the YMCA of Chicago for a camping center. It is rolling and 
mostly wooded with oaks, although there are a few small clearings 
including some open meadows in the low ground. bordering the oak 
woods at the edges of the clearings, and in the meadows, there are over 
400 peculiar cone-shaped mounds, some of them seven feet in diameter 
and three feet high.

These are anthills housing huge colonies of a rare species of ant, 
Formica ulkei. The worker-ants are about one-fourth of an inch long 
with black or deep-brown heads and pale reddish-brown bodies. They 
have long legs, are very active, and bite viciously.

An observer watched the ants from one of these mounds going back and 
forth between the mound and an oak tree in a stream about 3 inches 
wide. Going up the tree, they went out to the leaves to "milk" the 
honeydew from a species of aphids or plant lice covering the under side 
of each leaf. The aphids feed on the sap in the leaves and secrete this 
honeydew.

Heavily laden, the ants returned to the mound over the same trail. 
Others were bringing in grasshoppers, caterpillars and small insects.

At the urgent request of scientists, the YMCA has placed small signs 
beside many of the mounds, stating that this is a sanctuary for this rare 
ant of special scientific interest, and requesting that the mounds be left 
undisturbed.