38 
Psyche 
[Vol. 88 
year. Pogonomyrmex rugosus spreads reproduction out over the 
year to a greater extent than does P. montanus. Pogonomyrmex 
montanus produces relatively more sexuals than does P. rugosus or 
P. subnitidus and in general the production is much higher. 
Mating flights. 
The mating flights occur either in the morning (P. subnitidus ) or 
the afternoon (P. montanus and P. rugosus ). Reproductives of P. 
montanus first appeared on the nest surface on 10 August 1978. The 
reproductives emerged from the nest entrance, scurried over the 
mound for a few seconds and then returned to the nest. They may 
have been evaluating environmental conditions to determine when it 
was optimal for the mating flight. This behavior was found in all 
three species. A small flight occurred on 29 August 1978 between 
15:30 and 16:20, a second larger flight occurred on 9 September 
1978 between 13:20 and 14:10. The nests of P. montanus normally 
have a single entrance-exit hole. During the large flight on 9 
September 1978 the nests had 2.7 ± 0.3SE (12) exit holes per nest 
(range = 2 to 4). These supplemental exit holes allowed the 
reproductives to exit the nest more rapidly. I did not observe this 
behavior in the other two species. Reproductives of P. subnitidus 
were seen on the nest surface as early as 23 July 1980. The flights 
occurred on 6, 7, and 8 August 1980 between 8:00 and 9:30. In P. 
rugosus , reproductives first appeared on the nest surfaces on 1 
August 1979. A large mating swarm was observed on 24 October 
1979 between 14:00 and 15:00. 
During the time the reproductives left the nest, the surfaces of the 
nests swarmed with workers. Apparently most or all of these 
workers were foragers as they were lighter in weight than the other 
ants in the nest (MacKay, unpubl.). The reproductives often had 
considerable difficulty becoming airborne, especially the females, 
which usually climbed up plant stems before flying. 
Large mating swarms were observed in P. rugosus and were 
similar to those described by Holldobler (1976b). The males waited 
on the tops of hills (over 100 m altitude above surrounding terrain) 
for the females. The males displayed considerable competition for 
females as was shown by Markl et al. (1977). As a result mating was 
a frenzied activity in which numerous males competed for single 
females by biting, pushing, and in general attempting to exclude 
