122 
Psyche 
[June 
Materials and Methods 
This study was conducted from April 30-May 31, 1976 at two 
locations separated by about 0.7 km in the floodplain of the Salt 
River about 4 km south of Saguaro Lake, north of Mesa, Arizona. 
Both emergence sites were open areas with well-packed soil 
ranging from sand to clay in composition. These areas had a 
sparse covering of grasses with scattered shrubs ( Ambrosia del- 
toidea) and were bordered by mesquite (Prosopis sp.) and palo 
verde ( Cercidium spp.) trees. 
In order to follow the history of individual males, bees were 
captured with an insect net and given an identifying color com- 
bination of enamel paint marks on the dorsum of their thorax. 
Marking did not appear to disrupt the behavior of the bees seri- 
ously as most individuals quickly resumed their activities prior 
to capture. Six samples of patrolling males (N = 153) were col- 
lected and marked at Site 1 between April 30-May 15. Three 
samples totalling 76 males were taken at Site 2 from May 19- 
May 23. In addition, 47 hovering males were marked at Site 1 
from May 1-17 as well as 20 copulating males; at Site 2, 41 copu- 
lating males were captured and marked (all copulating males were 
believed to have been patrolling prior to copulation). 
Data on marked bees was gathered by censusing the study site 
on a daily basis from 30 April to 31 May with four exceptions (on 
two of the four days there was little or no male activity because 
it had rained heavily the night before). During the period from 
0800-1030 my assistants and I tried to recapture as many marked 
males as possible; sometimes when a male was seen on the ground 
digging it was not necessary to capture the bee in order to identify 
it. A map was made of Site 1 and the points where several bees 
were captured and recaptured were recorded on the map. In other 
cases, the distance between successive sightings of a male were 
paced off to collect information on the approximate length of 
movements by known individuals. 
Results 
Home ranges of patrolling males 
In large emergence sites dozens to hundreds of males may be 
present in the period from 0800-1030 cruising rapidly within a 
few cm of the ground. The patrolling males are not distributed 
