184 
Psyche 
[June 
they were of a single size and color. The resultant increase in num- 
ber of foraging hours each day enables a colony to quickly raise a 
brood to maturity within the very short summer season in alpine 
tundra environments. 
TIME OF DAY 
Figure 2. The mean head width of each sample of foragers shown as a function 
of time of day the sample was taken. Each point is the mean of 20 individuals in a 
sample. The correlation coefficient, r = 0.848, is significant at p < 0.005. 
Literature Cited 
Gregg, R. E. 
1963. The Ants of Colorado. University of Colorado Press, Boulder. 
Mani, M. S. 
1962. Introduction to High Altitude Entomology. Methuen and Co., Ltd., 
London. 
Taussig, W. H. 
1962. An ecological study of Formica neorufibarbis gelida Wheeler in the alpine 
tundra of Colorado. Unpublished thesis. University of Colorado. 
