84 
Psyche 
[Vol. 94 
actively herded the homopterans. Whenever an aetalionid moved 
away from the feeding group, the wasp quickly flew over the aetali- 
onid and assumed a stiff posture with stilt legs and elevated wings 
(N = 12). The wasp sometimes buzzed its wings and the aetalionid 
soon returned to its own group. The same type of behavior was 
observed in the wasp when attending membracid nymphs. 
Parachartergus fraternus responded to any approaching animals, 
including ants, conspecific wasps, anole lizards, and even humans. 
The typical display involved a combination of the following 
behaviors: positioning antennae low to the dorsum, extending wings 
laterally, buzzing wings, chasing, making stinging movements, or 
biting. These activities appeared to be successful in preventing most 
ants from soliciting honeydew from the homopterans. On one occa- 
sion, a wasp flew at an approaching myrmicine ant and actually 
knocked it off the branch. Workers of C. sexguttatus were observed 
frequently (on average once every 20 seconds during three six- 
minute periods) to descend the branch and petiole to a point 
approximately 5 cm from the wasp-tended homopteran aggrega- 
tion, but the mere presence of P. fraternus seemed to deter the ants 
from approaching closer. Unlike P. fraternus, most attendant ant 
species did not actively interfere with other approaching ants. One 
exception was C. abdominalis, the major nocturnal attendant, 
which pursued and disrupted any approaching ant of a different 
species. 
Ants tended in groups of two or three, whereas P. fraternus 
always tended alone. P. fraternus also tended much larger groups of 
A. reticulatum (19 and 25 individuals) than did ants (1 and 3 indi- 
viduals). For smaller membracids, however, there was no such 
trend; ants managed to tend groups of four to 24 individuals, while 
P. fraternus tended 12 and 13 nymphs. In wasp-tended aggrega- 
tions, when a wasp was momentarily absent, ants were often quick 
to move in and collect honeydew. Upon the return of the wasp, 
however, ants always retreated. 
A specialized anal tube of A. reticulatum enabled us to assess 
honeydew delivery. In response to vigorous antennation on the dor- 
sal tip of the abdomen by wasps or ants, aetalionids protruded the 
anal tube and secreted droplets of honeydew often at a high rate. We 
counted up to 34 consecutive droplets taken from an adult aetalio- 
nid during a single feeding bout by P. fraternus. Aetalionid 
