1926 ] Sequential Distribution of Formica exsectoides Forel 143 
cones, when as much as half the mound has been taken away 
completely. 
Presumably the greater work on the south side is connected 
with temperature or some other result of insolation. In general 
the ants are very sluggish in cool weather and very increasingly 
swift and active with high temperatures and we know from 
horticultural experience that any mound of earth in these lati- 
tudes tends to be noticeably warmer on the southerly expanse 
and this difference in temperature might be the reason for greater 
work put on that more sunny side just as Forel has assumed that 
the early morning sun on some European mounds enables ants 
to get to work earlier and so succeed in rearing more young on 
the easterly slope of a mountain than on the westerly slope. 
On the other hand the connection between sunshine and 
mound building may be much more complex as is suggested by 
the remarkable facts brought out by the investigations of this 
ant, Formica exsectoides, by foresters in New England. It was 
observed from 1912 onward that plantations of forest trees were 
found to show dead regions about ant-mounds and after some 
false clues it became evident that the ants took active part in 
killing the trees. 
H. B. Pierson (Jour, of Forestry, XX, 1922) described the 
actual actions of the ants in biting and stinging the small trees 
not far above the ground, resulting in death of the whole tree. 
In other trees the ants killed the 'leaves. Mapping the dead trees 
indicated that the ants killed the trees with reference to the sun, 
the trees being damaged most greatly on the east, west and south 
of the mounds. “As soon as the shadow of a tree was east on 
the nest for any length of time, that tree was attacked.” 
Some attacks of these ants upon vegetation near the mounds 
were seen in the Timonium colonies as follows. About each 
mound there is a well cleared area or moat on which most all 
vegetation is checked and surface material carried off till the 
underlying pebble or gravel is often exposed very markedly. 
When the strongly encroaching Japanese honeysuckle is rampant 
all over the adjacent area, its leaves and shoot tips are nibbled 
by the ants as soon as they encroach onto the mound or even grow 
within a foot of it. External to this circumferential band of de- 
