1959] 
Wilson — - Tandem running 
33 
greater than 30° and probably less than 20°. This angle was less 
than i° for the most remote targets. Thus the probability that pairs 
moving at random would hit one of the targets did not exceed 0.1 and 
was usually far less. The frequency of actual hits, 0.5, is highly sig- 
nificant. Furthermore, in each case of a hit, the pair at once broke 
apart and commenced feeding, indicating that recruitment was indeed 
the “goal” of their excursion. 
Although tandem running is apparently devoted in part or entirely 
to the communication of food finds, it is employed only by a fraction 
of workers engaged in successful foraging. Less than 10% of workers 
running from the nest to food masses were coupled in tandem pairs. 
This is in contrast to the high degree of participation shown by trail- 
laying ant species such as Solenopsis saevissima (Fr. Smith), in which 
more than 90% of workers returning from rich food sources con- 
tribute material to the trail. 
The nesting and foraging behavior of C. emery i Forel appears to 
be very similar to that of venustula. On two occasions, at Santurce 
and Luquillo, Puerto Rico, pairs of emeryi workers were seen engaged 
in tandem running, apparently identical in form to that of venustula. 
This aspect of the behavior of emeryi has not been analyzed further. 
Discussion 
The first mention of tandem running in the literature is evidently 
that of Hingston (1928). This author gives the following descrip- 
tion of foraging behavior in the Indian species Camponotus ( Orthono- 
tomyrmex) sericeus (Fabr.) : “This ant nests on the ground and 
goes up trees in search of food. Its plan of communication is very 
simple, and, being so simple, is highly instructive. All that happens is 
that one ant leads another to the place where spoil has been found. 
One ant discovers spoil. It returns to the nest, finds a comrade and 
leads it to the required place. The two go off over the ground. The 
leader keeps in front; the led ant follows. Number two keeps in num- 
ber one’s footsteps, and repeatedly touches its tail. The leader moves 
particularly slowly in order not to lose connection with its follower. 
If number two happens to get out of touch, then the leader halts and 
waits until number two regains its place.” In 1955, near Sydney, 
Australia, Mr. John Freeland showed me a pair of workers of an 
unidentified Camponotus engaged in tandem running quite similar to 
that in Cardiocondyla, although we did not guess the significance of 
the behavior at the time. Thus tandem running appears to be a wide- 
