178 
Psyche 
Methods 
[Vol. 93 
A major flight of A. versicolor occurred on 19 September 1985 on 
a study area in North Scottsdale, AZ 5.6 km north of Maricopa 
County along Pima Rd, approximately 3.2 km west of the McDow- 
ell Mountains. The habitat in this area is typical of the Sonoran 
Desert with Larrea tridentata and Franseria dumosa dominant 
shrubs and Olneya tesota and Cercidium microphyllum dominant 
trees along numerous shallow washes in the gravel/ sandy soil. A 
major storm front produced rain throughout the region the previous 
day; 2.6 cm of rain was recorded at the Arizona State Laboratory of 
Climatology located 32 km south of the study area. 
Habitat choice by A. versicolor queens was examined by running 
a transect 20 m long and 2 m wide from the base of 10 haphazardly 
chosen trees on the study area. Transect direction was chosen 
haphazardly. Distance of each starting nest from base of tree was 
recorded and standardized into “canopy units” by dividing by dis- 
tance from base of tree to outer canopy edge along each transect. 
This standardization was necessitated by variance in tree size and 
canopy extent. Distance to nearest neighboring tree was measured 
for 20 haphazardly chosen trees and converted to canopy units using 
the larger canopy extent of each pair. Number of queens per starting 
nest was determined by excavating 43 nests during this time. Addi- 
tionally, 21 starting nests were excavated on 22 September on a 
study area of similar habitat in South Mountain Park, Phoenix, 
AZ, 38.5 km southwest of the main study area. 
Effect of temperature in a starting nest on queen survivorship was 
determined by placing 18 queens (from the above excavated nests) 
in a large test tube plugged with cotton and containing a large ball 
of cotton saturated with water to prevent desiccation. Test tubes 
were placed in a darkened incubator at 20, 25,. . .45°C in random 
predetermined order; subsequently an additional tube was exposed 
to 42.5° C. To mimic late afternoon temperature exposures in the 
field, tubes remained at their given temperature for 2 hours. Queens 
incapable of righting themselves after 2 hours were considered dead. 
Likely temperatures in starting nests were determined by taking soil 
temperatures 5 and 10 cm below surface at the trunk base (0 canopy 
units), canopy edge (1 canopy unit) and in the open (> 1 canopy 
unit) on the main study area between 16:00 and 17:00 h on 24 
