82 
Psyche 
[Vol. 95 
this species have an even more efficient mechanism for reaching 
Formica colonies. Instead of a mating flight, winged P. breviceps 
queens copulate during the slave raids. The queens stop running 
momentarily, attract males with a pheromone produced in the man- 
dibular glands, mate and shed their wings, and then promptly con- 
tinue with the raiding workers to the target nest. 
Preliminary Field Studies 
This study was conducted at the Southwestern Research Station, 
located 5 km west of Portal, Arizona. At an altitude of 1646 m, the 
ground in this habitat is covered with bunch grass and contains 
extensive leaf litter from alligator juniper, Arizona oak, and Chi- 
huahua pine. A total of six colonies were monitored during the 
period when sexual individuals were present (July 15- August 10, 
1987). During each day, three of the colonies were observed contin- 
uously from 1400 to 1800 hr (MST). 
Males and queens of P. breviceps appeared outside the nest 1-2 hr 
before raiding, along with the milling workers, and ran around the 
nest perimeter. The males flew off intermittently during milling, 
until the onset of raiding. But we only observed two instances of 
flight by Polyergus queens, as compared with over 100 queens (from 
the six colonies) that mated in slave-raid swarms with no prior 
flight. This contrasts markedly with the related species P. lucidus , in 
which queens fly off 5-30 min after the males’ departure (Marlin, 
1971; Talbot, 1968). The number of alate queens running in the raid 
swarms ranged from 8-29 (n = 9 observations, x = 18). Although 
we could detect no obvious behavioral display, some queens 
vibrated their wings while running. At varying distances from the 
home nest, the queens ceased running. This inactivity was imme- 
diately followed by the appearance of highly-aroused males. The 
males ran erratically in circles, either around the queen or slightly 
off to the side. They often mounted each other. When a male finally 
copulated with the queen, she immediately pulled off her wings and 
continued running in the slave-raid swarm towards the target 
Formica nest. 
Preliminary field tests showed that squashing a Polyergus queen 
near a raiding column attracted males. To determine the source of 
the chemical attractant, queens were collected from slave-raid 
swarms and frozen. Using microdissection scissors, we sectioned 
