1967] 
Talbot — Polyergus 
305 
6:55 PM. Four morning raids were seen at the Lawn Nest in 1959, 
but this seemed unusual and no others have been observed. Within 
a colony, raid time also varied widely: from 3:06 PM to 5:16 PM 
for 0-26 and from 3:50 PM to 6:25 PM for the Lawn Colony. 
Second raids could start as late as 6:45 PM for 0-26 and 7:30 PM 
for the Lawn Colony. The latest ended at 8:14 PM. 
Colonies in fully exposed places where the sun was bright and the 
temperature high for longer time started their raids late. The 0-26 
raids were early because nearby trees began shading the nest while 
the sun was still high in the sky, thus reducing the temperature to 
that tolerated by the ants. Single individuals could run rapidly into 
the shade of nearby dense grass at almost any time of day, but the 
raiding group could not form until they could circle on the soil sur- 
rounding the nest entrance. The upper limit of tolerance for Polyer- 
gus was about 91 °F for air temperature 10 inches above the surface 
and 98 °F on the surface. (F. p. nitidiventris workers could forage 
normally at these temperatures.) 
Frequently during the morning or midafternoon an ant or two 
would stand at the entrance or move off to explore in the grasses. 
Then, in late afternoon, as the sun slanted low, or the nest was 
shaded so that both light and temperature dropped, ants began to 
come out one or 2 at a time. Sometimes the number increased grad- 
ually to full quota, but usually there would be a sudden outpouring 
which seemed to be in response to an incoming scout. Thus, the 
starting time of a raid was influenced by time and temperature and 
perhaps reduced light but seemed more directly dependent on the re- 
turn of an ant which had laid an odor trail. This seemed quite clear 
for the late raid which began at 5:16 PM. The ants had begun 
coming out at 4:10 PM when temperature was reduced to 9i°F.* 
From then on 20 to 50 kept exploring the edges of the nest but 
seemingly could find no direction to start out. Then suddenly at 
5:08 PM more ants poured out, covered the nest, and explored into 
the grasses until they had organized a raiding party which left at 
5:16 PM. It had seemed that weather conditions had been right, and 
the ants had been ready to start for about an hour before an odor 
trail was found. 
Even at favorable temperatures the ants did not raid until mid- 
afternoon. The earliest raid seen began at 3:06 PM at 8i°F (83°F 
on the ground). At 2:30 PM, when the watch began, there were 
^Temperatures are those 10 inches above the nest soil unless otherwise 
stated. 
