1968] 
Leuthold — Crematogaster 
341 
still alerts encountered nestmates all the way along. After many 
occurrences, however, the act of alerting typically decreases in in- 
tensity. As soon as the food finder reaches the side turn again, it 
changes from a rather fast run into trail-laying behavior. The ant 
either goes back to the food and returns again or turns nestward 
when only partway on the food bridge. If the movable side bridge 
is disconnected from the main path so that only the first food finder 
but no other newcomer ant can cross the connection, the recruiter 
then repeats its back-and-forth travel indefinitely (Fig. 4). Trail- 
laying behavior is always more intensive when the ant is moving 
away from the food. After an average of three return passages the 
trail is strong enough to lead a newcomer with accuracy to the food 
(Leuthold 1968). At the turn and the connecting joint from the 
old bridge to the new one, however, the pheromone marks from one 
run usually are strong enough to deflect new ants onto the base of the 
side bridge. Once they set foot on the side bridge they find the food 
mostly by random searching. 
THE ORGANIZATION OF MASS-FORAGING 
When a new food source is joined to the main passage bridge of 
a starved Crematogaster colony, as described in “Methods”, the 
maximum number of foraging workers at the food is usually reached 
after 10 to 90 minutes. Many factors are involved in raising the 
degree of mass-foraging, as follows. On an old, regularly frequented 
trail there is a low percentage of workers deviating from the trail. 
This is an important aspect leading to the discovery of new food 
sources. The percentage of deviating workers is fairly constant over 
Fig. 5. Food recruitment experiment (arrangement: see “Methods”). 
In the first phase of 32 min all newcomers were removed from the food. 
In the second phase, however, foragers were allowed to return and recruit 
nestmates. 
A. Number of passages in both ways per min on the main bridge between 
food bridge and nest. 
B. Percentage of ants deviating from the main bridge to the food bridge. 
C. Number of newcomers to the food per min (Circles: actual number. 
Curve: moving average as in A). The number of newcomers 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, 
supposing repeated foraging of each food finder. 
D. Number of passages per minute towards the food during the recruit- 
ment phase, averaged to linear rise. 
E. Diagram (C) averaged to linear rise. 
F. Average number of newcomers calculated proportionally to the in- 
crease of passages in (A) makes only 25% of the actual number in 
(E). 
