1958] 
Wilson — Chemical Releaser 
43 
Description of Alarm Behavior 
When workers of Pogonomyrex badius are disturbed by 
alien mechanical or chemical stimuli, they show the follow- 
ing characteristic alarm response. Low intensity : rate of 
locomotion increases, with the ant moving in wide, poorly 
defined loops and circles; the head and antennae are 
periodically lifted high and the antennae waved about; the 
gaster may be periodically lowered so that its long axis 
is approximately perpendicular to the ground surface. High 
intensity : rate of locomotion increases still more, with the 
ant tending to move in tighter and more geometrical circling 
patterns; the head and antennae are periodically raised a 
moderate distance, but not as high as during lower in- 
tensity alarm; the mandibles are held partly open; the 
gaster may be periodically bent downward. 
These two states of activity are not discontinuous but 
merely represent points on a gradient of intensity that is 
a function of the magnitude of the stimulus applied. Es- 
sentially the same pattern of behavior is exhibited both 
inside the artificial nest and outside it in the near vicinity 
of the nest entrance. Under laboratory conditions, the in- 
tensity of response outside the nest is inversely related to 
the distance of the locus of stimulation from the nest en- 
trance. At the outer limits of the foraging arena, approxi- 
mately one meter from the nest entrance, high-intensity 
responses have been difficult to induce, and workers have 
frequently shown instead a simple escape reaction. 
A highly excited worker is a potential cause of a wave 
of alarm behavior among other workers- Under natural 
conditions a single worker exhibiting high-intensity alarm 
just outside the nest entrance can initiate general excite- 
ment that spreads centrifugally over the entire surface of 
the nest crater, along a radius of fifty centimeters or 
more. As the first worker commences a circling movement, 
it encounters other workers, which are stimulated to take 
up smiilar movement, in turn exciting other workers, and 
so forth. The wave of excitement seems to diminish in 
intensity away from the original stimulus in a roughly 
logarithmic fashion. 
These results can be closely duplicated in laboratory 
