1981] 
Edwards — Phidippus my s face us 
203 
For each sound sequence, both palpi become engaged nearly 
simultaneously by a backward movement in which the palpi appear 
to be dragged along the surface of the substrate for a distance of 
about 1 mm. Halfway through the backward movement, the cymbia 
are bent backward at an angle to the palpal tibiae (Fig. 3). At the 
end of the backward movement, the palpi remain stationary for a 
fraction of a second while the cymbia are rotated outward (left 
palpus clockwise, right palpus counter clockwise). The palpi are 
then returned to their most anterior position, apparently by lifting 
the palpi from the substrate and moving them forward. When the 
palpi are in their most anterior position, they are clearly off the 
substrate. A single cycle of palpal movement is approximately 0.8 
second (5 frames at 6 frames per second). 
Audiospectrograms indicate that 13-20 (x = 17, n = 8) paired 
stridulations are made consecutively, separated by pauses subequal 
in timing to the sound sequences (Fig. 4). Alternation of stridula- 
tions and pauses occurs at the rate of 1.5 sound sequences per 
second (at approximately 25° C). 
Fig. 3. Diagrammatic illustration of movement of left palpus (ectal view) by male 
P. mystaceus during stridulation. A. Anterior position. B. Backward movement, 
during which cymbium is bent backward, moving fan-shaped file across plectrum. C. 
Rotary movement, during which macrosetae are engaged in substrate and cymbium 
is rotated outward, moving linear file across plectrum. F = File cavity, T = Tibial 
apophysis. 
