1972] 
Topoff , Lawson & Richards — Eciton 
359 
consisted of a circular chamber (5.0 cm in diameter, 1.4 cm high) 
which opened into a tunnel that was 7.9 cm long. The tunnel was 
the same height as the adjoining circular chamber, and was 1.2 cm 
wide. This width was chosen because it was approximately equal to 
the leg span of the intermediate-sized workers of E. hamatum and 
E. burchelli ( i.e., workers whose overall length was between 7.0 and 
9.0 mm). The curvature of the tunnel was equal to that of the 
trail. 
The circular chamber was divided approximately in half by a 
vertical partition attached to its lid. Each test ant entered the cham- 
ber through a hole in the lid, and the partition prevented it from 
contacting the trail during the 15 second period in which it was al- 
lowed to adapt to the chamber. At the end of this interval the lid 
with the partition was replaced with another lid without a partition, 
thus allowing the ant access to the trail. 
For each dilution of ether extract that was used, 60 intermediate- 
sized ants (30 callows and 30 mature adults) were selected at ran- 
dom from the mass of ants in the aquarium. The dilutions were 
prepared by adding different amounts of pure ether to the extract. 
Ants were tested individually, and as indices of trail following we 
recorded the number of ants following, the distance travelled on 
the trail (maximum distance = 580 mm), and the speed of travel 
along the trail. If an ant did not leave the runway at the end of 
one minute, a negative response was recorded. 
Results 
The results of comparing trail-following performances between 
callow and mature adult worker ants from three colonies of E . 
hamatum and one colony of E. burchelli are shown in Table 1. 
It is clear that when comparisons are made as to the relative ability 
of callow and mature adult ants to follow any portion of the trail, 
as well as comparisons of the number from both groups able to com- 
plete the trail, the differences are not significant in approximately 
two-thirds of the cases. The third measure of trail following we 
considered was the median distance (in mm) followed by callow 
and mature adult ants in each test series. Again, these differences 
were usually not significant. The only measure of trail-following 
performance that consistently illustrated the behavioral immaturity 
of the callows was their speed of running over the trail. At all 
dilutions on all nomadic and statary days in which tests were con- 
ducted, the running speed of the callows of both species was slower 
than that of the mature adult ants. 
