32 
Psyche 
[September 
A total of 1 6 tandem trips away from the larger venustula nest 
were followed to completion. Two of these were abortive, breaking 
off less than 15 centimeters from the nest. Seven led outward for 
distances of approximately one to two meters from the nest, in four 
cases to food baits set at this distance. The remaining seven led for 
three to five meters before breaking up or ending at a food source, a 
very considerable distance for so small an ant. All of the movements 
formed a nearly straight line, with only occasional, momentary 
doubling back. Eleven of the tandem runs ended without achieving 
any obvious goal. Five, however, ended at food sources, either dead 
insects occurring naturally or baits set by the author and both workers 
thereafter commenced feeding. Considering the greatly dispersed 
state of acceptable food, this seemed to be a highly significant propor- 
tion of “hits”. Furthermore, almost all of the eleven fruitless runs 
were oriented in directions from which abundant food particles were 
being transported by other workers at the time. 
The hypothesis was now considered, that tandem running is a 
means whereby newcomer ants are recruited to new food sources. This 
implies that the leader ant has visited the food source at least once 
and is now returning, bringing a sister worker in tow. The hypothesis 
could not be tested directly under field conditions, since workers were 
too small to mark with ink or paint and could not otherwise be traced 
when they re-entered the nest. However, the following indirect ex- 
perimental evidence supports the hypothesis. 
Baits were placed at varying distances from the nest and tandem 
pairs leaving the nest were followed during the next 30 or 60 minutes. 
In one experiment a small piece of moistened sugar was placed 10 cm. 
from the main nest entrance. Two tandem pairs left in the observa- 
tion period ; one arrived at the sugar, the other proceeded to a dead 
homopteran lying naturally at a position about 4 meters away. In 
two additional experiments, small, freshly killed moths were placed 
at positions 15 cm. and between one and two meters from the nest. 
Three tandem pairs arrived at these baits, while 5 moved in other 
directions. Thus in all three experiments five pairs arrived at targets 
and commenced feeding, while five went in other directions. Even if 
it is assumed that the five that missed were not heading for other, 
natural food sources, an unlikely proposition, the results are highly 
significant. Judging from the movements of individual workers ap- 
proaching and passing baits in near-misses, the total angular sector 
through which individual (and tandem pairs) could move randomly 
outward and successfully hit the closest target was calculated as not 
