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Psyche 
[December 
Fig. 6. Two experiments in which identical side bridges were joined to 
the main pathway, one bearing a trail, the other one blank. The deviation 
rate to the trail bridge is significantly higher than to the blank bridge 
(Student’s test p < 1%). 
periods in the range of hours and comprises less than 6% of all by- 
passers unless the colony is extremely starved or has been recently 
disturbed. During the period of recruitment the number of devia- 
tions from the pathway rises dramatically. Only 15% of all new- 
comers during the recruitment phase in the experiment of Fig. 5 can 
be accounted for by basic deviation and as little as 5.3% in the 
adequate experiment shown in Table 1. Hence the existence of a 
recruitment message is obvious. One of the main factors of mass- 
recruitment caused by the alerting of the food finders is the increase 
in running activity of the colony measured by the number of workers 
passing over the main bridge (Fig. 5 A, 7 A, 10B). The sum of 
deviations calculated proportionally to the increased running activity, 
however, yields only 25% of the actual number of newcomers in the 
experiment of Fig. 5F and 28% in the experiment presented in Table 
1. The increase of the deviation rate is represented in Fig. 5B. A 
second important factor for mass-recruitment is found to be the 
pheromone trail between main bridge and food which is built up in 
the beginning of the recruitment phase. To demonstrate the signifi- 
cance of a trail on a side bridge the following experimental situation 
was arranged : two identical side bridges, opposite each other, were 
joined to the main bridge, one bearing a good natural trail (from 
another ant colony), the other one blank. In a second experiment 
the arrangement of both bridges was interchanged in location. The 
basic deviation of ants onto the two kinds of bridges was counted 
during a period of 42 and 30 minutes respectively. All ants were re- 
moved from the bridges. In both experiments the number of new- 
comer ants was significantly higher (Student’s test p < 1%) on 
the trail bridge (Fig. 6. In the first experiment the deviation rate 
increased 3.7 times, in the second 7 times). Hence a trail on a side 
bridge is a powerful component that increases the deviation rate of 
ants from the old pathway. A trail has, however, only directing 
quality (true attractant: see “Introduction”). No alerting stimulus 
