1968] 
Leuthold — Cremcitogaster 
347 
ing stimuli released on the pathway temporarily increase the activity 
of the recruited ants but their effect fades if the stimuli are not 
renewed (see “Behavior”). This is the case when the recruiter turns 
back again to the food before reaching the nest. If, however, the 
alerting behavior is performed in front of the nest entrance or even 
within the nest twigs, the colony activity increases significantly (Fig. 
io). Excited workers leave the nest in large numbers and start 
running over the bridge. In the meantime other foragers which had 
found the access to the food come back onto the main bridge. They 
strengthen the new trail. The returning ants often accumulate at 
the joint from the new bridge to the old pathway because of intensive 
trail-laying. More new ants again are attracted towards this cluster 
and follow the fresh trail. All returning foragers in this stage alert 
encountering ants. The excitement and colony activity increase 
exponentially since the more recruiters on the path the stronger the 
recruitment effect becomes. All ants who find the food directly turn 
Table 1. Food recruitment experiment. (Arrangement see: “Methods”). 
Phase without re- 
cruitment. (AH 
ants were removed 
from side bridge). 
Phase of 
recruitment 
54 min 
per 1 min 
68 min 
per 1 min 
Running frequency 
on the main bridge 
(passing ants both 
ways) 
162 
3 
1096 
16 
Actual number of 
newcomers* to the 
side bridge 
7 
0.13 
167 
2.46 
Calculated number 
of newcomers, sup- 
posed without any 
recruitment stimulus 
7 
0.13 
8.8 or 5.3% 
of the 
actual 
number 
0.13 
Calculated number 
of newcomers pro- 
portional to the 
increase of running 
frequency on the 
main bridge 
7 
0.13 
47 or 28% 
of the 
actual 
number 
0.69 
^Supposing repeated foraging of each food finder, the number of new- 
comers during a 2 min period was obtained by the number of ants 
going to the food minus the number of returners during the preceding 
2 min period. 
