6o 
Psyche 
[March 
taneously on top of the nest and left there for 20-22 hours. Because 
the cardboard covering the hole on top of the stopper was the only 
material the ants could remove in attempting to reach the trapped 
workers, all their digging activity was directed towards these areas. 
After each test, the pieces of cardboard were therefore removed and 
the “damage” done to them by the digging ants examined. The 
following scoring system was used to quantify the findings: 
0 : No visible chewing marks on the surface of the cardboard 
1 : Superficial chewing marks 
2 : Heavy chewing marks 
3 : Only a transparent film of cardboard remains at the site of 
digging 
4 : The diameter of the hole dug is < i mm 
5 : The diameter of the hole dug is > i mm 
6 : The diameter of the hole dug is > 2 mm 
7 : The diameter of the hole dug is > 3 mm 
If the ants worked on more than one place, the different scores were 
added. Each test was repeated at least five times. 
Results 
Fifteen to thirty minutes after the bottles were placed on top of 
the nest, some workers could be observed palpating the surface of 
the cardboard-seal on the test-tube with their antennae. Others just 
rested on this place for a few minutes, their antennae slightly raised. 
Suddenly, a single ant started to work on the cardboard with its 
mandibles, rather hesitating at first, but gradually with more vigor. 
When one individual became involved in such activity, it soon was 
joined by at least another ant, and occasionally I noticed up to ten 
workers chewing at the same spot. The digging ants sometimes were 
replaced by other nestmates after various times, or they continued 
working until a hole was punctured. Very often, however, they 
abandoned this behavior before an opening was created, leaving only 
chewing-marks of different intensities. 
Table 1. Result of the digging behavior released by trapped 
workers, females, males or brood (larvae and pupae approx. 1:1). 
The mean activity is based on eight repetitions. 
Average digging 
Trapped individuals 
response 
Range 
200 workers 
5-6 
5-6 
15 winged females 
5.0 
2-8 
20 winged males 
4.6 
2-6 
200 larvae & pupae 
4.6 
2-6 
Control 
0.4 
o -3 
