302 
Psyche 
[December 
MEANS OF LOCATING COLONIES TO BE RAIDED 
Polyergus raids were definitely not exploratory forays. There was 
no set pattern of pathways. The ants went directly to the nest to be 
raided (except that they might follow a, contour of the land), and a 
nest visited twice on different days might be approached by quite 
different routes. This suggested that individual ants do the scouting 
and locating of colonies. This was verified, to my satisfaction, during 
the study. Observations made on July 6, 1965, gave an especially 
clear picture. During that morning an occasional Polyergus worker 
appeared on the surface; but between 11:15 AM and 2:55 PM none 
came out, although the temperatures were not especially high (8i°- 
85°F 10 inches above the surface and 9i°-95°F on the surface). 
At 2:55 PM 3 workers emerged, moved huriedly across the bare 
soil and disappeared into the grasses. For the next 40 minutes there 
were one or 2 Polyergus on the nest area at all times, and at least 
10 of these slipped off into the grasses. Gradually more Polyergus 
joined those on the nest until there were 3 to 10 running about, and 
2 per minute left the nest until 4 PM. After that time most stayed 
on the nest and only a few left, but in the whole time from 2 :55 PM 
to 4:15 PM 52 ants were seen to depart. During this time none re- 
turned. Then at 4:15 PM a Polyergus was seen 3 feet from the 
nest, coming directly home. It went into the nest entrance, and 
within a few seconds a whole stream of ants began pouring out. They 
spread thickly over the nest area and within 5 minutes had started 
a raid to the west where the scout had come in. 
On other days the departure of scouts was less conspicuous, and 
seldom was one lucky enough to spot a scout coming in. But when- 
ever an ant came in hurriedly from the grass and went directly into 
the nest, there was an outpouring of ants. It was thus assumed that 
whenever a sudden emergence occurred it was in response to a mes- 
senger arriving with news of a located colony. If this was correct 
and if the scouting ant, which found a colony, laid down an odor 
trail on its way home, then the odor must have been quite long last- 
ing, for it sometimes took an ant 30 to 45 minutes to return from a 
raided nest. It seemed unlikely that a raiding group could be follow- 
ing anything but an odor trail, for it moved rapidly, did not maintain 
leaders, and usually stopped at exactly the right place. 
In contrast to raiding activity, which seemed mechanical and 
stereotyped, activities of workers while scouting for colonies must 
require a high degree of individual action and response to the con- 
