150 
Psyche 
[December 
Summary. 
The ant Formica exsectoides constructs mounds in wooded 
regions. Observations made near Baltimore Md. show that the 
distribution of mounds occupied by a large community of colonies 
varied through the years 1905-1926, older mounds being replaced 
by newer ones in adjacent territory. 
Individual mounds may persist many years or may be aban- 
doned from unknown causes; but in general there seems a cor- 
relation between mounds and forest growth; new mounds arise 
in new forested regions and old mounds become vacant in older 
forests. 
The history of a colony is coordinate with tree life, and in 
general will be briefer. It is inferred that the organic relation 
between tree and ant colony is sequential; the new ant family or 
colony obtaining food from younger trees (the growth of some of 
which they may prevent); the older colony having to contend 
against the greater shade and lesser food supply from the older 
trees, may be unable to continue existence except by migration 
into younger stages of forestation. 
The “ tree-ant- association ” is complicated by such birds 
as frequent certain stages of forest growth and do destroy such 
ants. 
