1979] 
Chadab — Warning Cues for Social Wasps 
117 
As soon as army ants approached within several centimeters of a 
P. exigua nest, wasps rushed to the lower nest surface and adjacent 
leaf. One to several wasps fanned their wings intermittently, and 
simultaneously produced a buzzing sound. Within seconds other 
wasps joined in the sound production, and the initial disorganized 
fanning and buzzing became regular, synchronous pulses. This com¬ 
plex synchronized behavior is termed “group fanning.” The buzzing 
was most likely produced by the vibration of the thoracic skeleton 
by the indirect flight muscles. Fanning without sound production is 
a generalized behavior pattern, but fanning with buzzing was 
observed only in alarm situations. 
Not all the wasps in the colony participated in the alarm: the 
number varied from several to 20 or more, depending in part on the 
strength of the alarm stimulus. Each buzz was about 0.9 sec long, 
followed by a 1.3 sec pause, and during its production the tip of the 
wasp’s gaster was pressed to the substrate with head and front legs 
lifted (Figs. 1, 2). Between pules the body returned to the normal 
Fig. 2 Protopolybia exigua participating in group alarm: front legs raised, wings 
fanning, and gaster pressed to substrate. A few wasps may begin the alarm; others 
join in. 
