306 
Psyche 
[Vol. 92 
being carried upslope in a nuptial flight. The actual location of the 
mother colony was probably some tens of kilometers downslope, in 
the grassland-lower montane transition zone (sensu Marr, 1967), 
where deciduous trees are mixed with pines. The altitude of this 
zone ranges from 1700 to 1825 m as in the Front Range. 
Colonies of D. taschenbergi , consisting of thousands of individu- 
als, prefer to build their nests in sandy soil of partly open wooded 
areas or at the edge of woods. The entrance is usually covered with a 
low mound of thatch composed of either grass, twigs or needles 
(Creighton 1950, Smith 1979, Wheeler and Wheeler 1963). Such 
nests were observed in Quebec in mixed hardwoods with pines 
either on rocky grounds or on morainic and fluviatile sand deposits 
(Francoeur, unpublished data). Workers forage in typical files and 
actively collect sugary secretions of coccids and aphids on trees and 
bushes, or scavenge dead arthropods. Bradley and Hinks (1968) 
reported this ant attending aphids on jack pine in Manitoba. 
These ecological and ethological traits were likely the same at the 
time when the reported fossil was living. At about 8000 yr. BP, 
altitudinal tree limit has apparently already reached the Lake Isa- 
belle cirque basin, subsequent to deglaciation. The faunal evidence 
from insect fossil assemblages of this age from the Colorado Front 
Range suggests that climatic amelioration was well underway by 
this time, with mean July temperatures (an estimate of summer 
warmth) as warm or warmer than modern values (Elias, 1983, 1985). 
Acknowldgements 
We wish to thank Dr. W.M. Briggs for preparing the scanning 
electron micrograph of the fossil specimen and Dr. F.M. Carpenter 
for making a reverse lighting print. Funding for paleoecological 
research at Lake Isabelle was provided by a U.S. National Park 
Service Contract, #CX-1200-2-B048, and by a National Science 
Foundation, Long-Term Ecological Research Grant, BSR-80 12095. 
Mr. R. Loiselle mounted and took the micrograph of the recent 
specimen. Taxonomic study of ants was made possible through a 
research grant from the National Sciences and Engineering Re- 
search Council of Canada. 
