1932 ] 
Distribution of Formica ulkei 
131 
Test-location 
Date 
Time 
Foot-candles 
Open margin 
.. 8-21-31 
9:45 A. M. 
2400 
Open margin 
. 8-26-31 
9:45 A. M. 
1750 
Forest clearing 
8-21-31 
9:55 A. M. 
2260 
Forest clearing .. 
8-26-31 
9:55 A. M. 
1665 
Shaded forest 
8-21-31 
10:05 A. M. 
44 
Shaded forest 
. 8-26-31 
10:05 A. M. 
18 
The data of the 
table indicate that both 
margins and 
forest clearings are receiving essentially similar sun-radia- 
tions, while the shaded forest floor receives very low foot- 
candle intensities. There is no difference between the open 
meadow and the open margin of the forest. Relating these 
data to the fact that active nests are abundantly found 
along the open forest margins, in the open, or in clearings 
and are not located in the shaded forest areas, the conclu- 
sion is suggested that light intensity plays a definitely posi- 
tive role in that a certain range of light intensity, i. e. of 
unobstructed sun, is favorable to mound building. 
Such a distribution of the nests with respect to light in 
the visible range, also connotes a correlation between nest 
location and temperature; the latter being, in part, an 
expression of sunlight. The relation of temperature to 
mound nests of Formica exsectoides which are essentially 
similar to those of Formica ulkei has been treated by An- 
drews (1927). This investigator found that the tempera- 
tures of the upper part of the mound were higher than 
those of the lower part, and that these internal tempera- 
tures vary daily being due to heat received from the sun. 
These observations are in accord with our own. Andrews 
(1926) has also noted that Formica exsectoides nests in- 
crease in sunny regions and decrease in shaded areas; a 
further indication of the role of sunlight and temperature 
in connection with ant mound distribution. 
The effect of soil moisture content on the nest distribu- 
tion becomes a limiting factor only in the region of the 
marshlands which exist in some of the lanes between the 
forested areas. Here the surrounding substratum, for some 
thirty feet about its center, is too moist to permit nest 
building. Apparently the greater soil moisture of the lower 
