180 
Psyche 
[Vol. 93 
CANOPY UNITS 
Figure 1. Habitat choice by Acromyrmex versicolor queens. “Canopy units” 
represent distance of a starting nest from the base of tree divided by distance from 
tree base to outer extent of canopy along that transect. 
contained 3 queens from one site only, and the last contained a 
solitary foundress. 
Discussion 
The distinct habitat choice of A. versicolor queens (Fig. 1) seems 
a likely response to high soil temperatures in sunlit areas during the 
mid-late summer flight season of this species. Queens initiating nests 
in open areas will likely experience lethal temperatures even 5 cm 
below the soil surface. We routinely found queens at this depth 2-3 
days following the mating flight. These nests, however, were located 
under trees where potentially lethal temperatures were never 
recorded. Acromyrmex versicolor queen death after 2 hours of 
exposure to temperatures 40-43° C is consistent with upper temper- 
ature tolerances of foragers of this species of 42-43° C (Gamboa 
1976). 
Queens of several other ant species display varying degrees of 
habitat choice. Queens of Lasius niger and Lasius flavus both prefer 
bare, sunlit soil where they establish colonies more successfully than 
