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[Vol. 92 
Figure 1. Map of fossil locality near Lake Isabelle, Colorado Front Range. 
posterior half of head, and the blackish coloration are strongly 
congruent. Though partly obscured punctures, foveolae and faint 
striations are visible on genae and clypeus; the amount of sculptures 
varies on these parts in recent specimens. The presence of three 
ocelli identifies a gynomorph. 
In the Nearctic region, the four representatives of the ant genus 
Dolichoderus belonging to the subgenus Hypoclinea are found only 
in the eastern half of the continent, from southern Canada to the 
Gulf States in U.S. (Smith, 1979). They are mainly associated with 
the deciduous forest biome and the transition zones with the boreal 
coniferous forest. The known range of D. taschenbergi covers the 
northern half of that territory with sporadic occurrences in the west 
from southern Manitoba to South Dakota. One might predict the 
rare occurrence of this insect in northern Colorado, but it is not 
reported there by Gregg (1963). He considers the genus as extinct in 
that state and concludes that it was an element of the Pre-glacial 
tertiary ant fauna. The discovery of the fossil head of Post-glacial 
age suggests a rather recent extinction from Colorado, if at all. 
As noted in the discussion of fossil beetle taxa from the Lake 
Isabelle sites (Elias, 1985), it appears certain that a considerable 
percentage of the winged insects preserved in high altitude fossil- 
bearing deposits are derived from downslope regions, and were car- 
ried upslope by mind currents. The fossil specimen of the ant D. 
taschenbergi was probably deposited in the Lake Isabelle basin after 
