1958 ] 
Wilson — Chemical Releaser 
49 
employed by vertebrate ethologists (Tinbergen, 1951). It 
arises out of what can properly be called a conflict situation, 
during which workers become highly excited but encounter 
no object against which aggressiveness can be released. 
However, it should be noted that such behavior may well 
be functional under certain conditions. Experiments with 
substitute chemical agents, described in the next section, 
show that the digging becomes directional when the stimu- 
lus is confined to a single locus. It is probable that a worker 
buried by a cave-in will release mandibular-gland secre- 
tion ; this becomes virtually certain if the cave-in is caused 
by the intrusion of some larger animal. As a result, it 
can be predicted that excavation following a major dis- 
turbance of the nest will tend to be directed toward those 
parts of the nest where workers are trapped. This hypothes- 
is remains to be proven experimentally. 
The Effects of Alien Chemical Stimuli 
Apparently a wide variety of relatively volatile chemical 
agents are capable of inducing behavior patterns similar 
or identical to those released by the mandibular gland 
secretion. When groups of workers were allowed to come 
into direct contact with small amounts of formic acid, 
ethylamine, w-butyric acid or n - caproic acid absorbed in 
one- centimeter-square pieces of filter paper, they respond- 
ed immediately with alarm behavior and in time with 
digging behavior. Further, the digging was concentrated 
around the paper squares- The ants made no attempt to 
remove the squares but instead tended to dig shallow 
trenches around them. When triethanolamine, ammonium 
sulfide, phenol, and oleic acid were tested in the same 
way, the ants either showed no reaction or (in the case 
of oleic acid) removed the paper square to the refuse pile 
of the foraging arena. When ethylamine and w-butyric acid 
were allowed to evaporate in the near vicinity of resting 
ants, so that these substances could be detected only by 
olfaction, the ants again responded with alarm and digging 
behavior. But in this case the intensity of the behavior 
was distinctly less than that following direct contact with 
the absorbed chemicals. It was also significantly less than 
