1967] 
Talbot — Polyergus 
303 
figuration of the surroundings, which results in the ability to come 
home directly after a nest is found. 
Experiments made in 1966 and 1967 seem to verify the odor-trail 
theory. On August 16, 1966, 10 Polyergus workers from nest 0-26 
were crushed in dichloromethane to extract pheromones. Next day 
the colony was visited at 3 130 PM when early preraid activities were 
beginning, with a dozen Polyergus circling about the nest area and 
surrounding grasses. A pheromone trail, laid down with a small 
brush, was extended from the nest for 3 feet. Instantly ants began 
to follow the brush; and by the time the trail was complete, 50 ants 
were upon it. More came from the nest, and in 5 minutes there were 
about 75. Each ant ran forward and backward and from side to side, 
crossing and recrossing the odor trail, just as they did on their own 
raiding trails. At trail’s end they ran forward and to each side, as 
they did when one of their own trails ended without leading to a nest. 
Then, finding nothing, they began to return home ; and in 25 minutes 
all but 10 had abandoned the trail. There had been no outpouring of 
ants from the nest (the odor trail began at nest edge), and ants did 
not mass in a typical raiding formation. But each ant, going singly 
on the trail, had acted in characteristic fashion. 
The same pheromone solution was then taken to another colony 
(M-26), which had ants out in preraiding activity at 4:23 PM. A 
trail 6 feet long was made; and again ants followed the brush im- 
mediately, moving back and forth and from side to side along the 
trail. In this case about 100 ants were attracted. Again they came 
along the trail singly, explored a little beyond it, and returned when 
no nest was found. 
On August 20, 1966, a trail was attempted under conditions when 
no ants would normally be out. A dichloromethane solution of 10 
crushed ants from M-26 was used. The Polyergus colony was visited 
when it was still in hot, bright sun. No Polyergus were in sight 
until the nest was shaded. Within 10 minutes about 25 Polygerus 
were running about, keeping in the shade. A short trail, stretching 
12 inches out onto the hot soil, induced those crossing it to follow; 
but they came back almost immediately. Subsequent trails were ex- 
tended out in different directions for 4, 7, and 1 1 feet. In each case 
ants followed these trails, although the soil was still hot enough to 
prevent ordinary raids. 
It was found that dabs of solution worked as well as a continuous 
line, since ants found them readily as they zigzaged back and forth. 
Putting the brush into the nest entrance caused 25 to 30 ants to come 
