1926] Sequential Distribution of Formica exsectoides For el 145 
mounds are most permanent and successful in places exposed to 
the sun and less successful in deep shade. Thus the upgrowth of 
trees would eventually introduce an adverse element in the per- 
manence of the mound as being hostile to the optimum tem- 
perature needed. 
Attempts to establish transplanted mounds both in city 
back-yard and in the old forest at Homewood, in 1906, 1916 and 
again in 1926 proved futile; some communities of this ant, 
Formica exsectoides planted at Homewood at various seasons of 
the year were decimated by birds, especially robins and flickers. 
Thus one influence of forestation upon this ant will be 
through the bird fauna of the forest; for where the robin is 
favored by the vegetation there can not be good stands of these 
ant dwellings and when the trees have grown so large as to 
furnish not only food but nesting sites for flickers, this ant cannot 
be expected to flourish; hence again the older forest will be 
inimical to Formica exsectoides. 
Some of the facts as to association of trees and ant mounds 
are represented more in detail in the second diagram-map which 
embraces only the middle western part of the whole area in- 
dicated in the first diagram-map. 
The area mapped in the second diagram is about four acres 
of sterile sandy iron soil from former iron ore pits, spread out in 
a flat with steep bank running down to the York Road on the 
west and roughly outlined to the east by abandoned wood 
roads. 
In 1905 this was largely a bare barren expanse with little 
vegetation, few trees and about fifteen ant mounds; but by 1920 
trees had come in over its eastern half and ant mounds had 
scattered all over it as roughly suggested in the first diagram. 
Both trees and mounds extended into the area from the east. 
The first map shows that in 1905 these four acres had many 
deserted mounds in the easterly part and some occupied mounds 
in the middle part, but that in 1920 the population was chiefly 
in the western part and made up of active mounds while many 
mounds in the middle region had disappeared. 
Along with this advance to the west and dying off to the 
east there was a fifteen year growth of trees which is indicated 
