6 
Psyche 
[March 
workers, a major and two minors, approached along the main trail 
and, on reaching the junctures of the new trails, departed down them 
for various distances. The major went all the way to the insect and 
prowled around it for several minutes before returning to the main 
trail. In two subsequent replications of the experiment, two of 
thirteen and one of five Camponotus workers passing along the main 
trail were deflected onto the Azteca side trails during the period of 
peak Azteca response to the baits. Such deviations from the main 
trail were never observed except at this time. It was concluded that 
the Camponotus respond to the Azteca communication. 
The following observation led to the further conclusion that the 
Camponotus were tracking the Azteca olfactorially rather than 
visually. Occasionally around midday the Azteca were unusually 
scarce on the main trail, while the Camponotus remained moderately 
common. Stretches of 30 to 50 cm. of the trail were often bare of 
Azteca, but many individual Camponotus followed the established 
track just as well. On close examination I found no alterations in 
the surface structure of the main trail, other than the postulated 
chemical one, that could have supplied the Camponotus with a clue. 
Although the Camponotus beebei utilize Azteca trails extensively, 
the following observation shows that they have maintained their own, 
private trail system. On a single occasion in February a line of seven 
Camponotus were seen moving along the main Azteca trail. Four of 
the workers ran in a tight group directly behind the leader, frequently 
advancing enough to touch the abdomen of the ant ahead. When the 
leader was touched, it dashed forward at a faster pace over a short 
distance. This part of the behavior was typical of communication by 
“tandem running”, which I have described earlier in a paper on the 
genera Cardicondyla and Camponotus (Wilson, 1959). The re- 
maining two workers followed at a greater distance, tracing each 
twist and turn taken by the leader. During the next 15 minutes 
several other Camponotus workers passed the same way, again tracing 
parts of the route of the leader with close fidelity. After that time, 
new Camponotus workers continued to run on the Azteca trail but 
ignored the Camponotus trail. There could be no doubt that the 
lead ant had secreted an odor trail of the recruitment type (see 
Wilson, 1963). It was laid on top of the Azteca trunk trail, which 
for most of its length was about 10 centimeters wide. Equally 
interesting was the fact that only the Camponotus responded to it. 
The Azteca workers continued to pass along their own trail during 
the episode but failed to orient to the inner track followed so closely 
