206 
Psyche 
[Vol. 88 
appeared to be similar in timing to stridulation), but the palpi were 
not in contact with the petri dish, and no audible sound was 
produced. 
Discussion 
Known reproductive behavior of the males of species of Phidip- 
pus involves a male locating a female by visual or chemotactic 
means (Richman, in press), a visually-oriented courtship by the 
male consisting of a series of movements with the legs I and palpi 
(usually while advancing in a zigzag path), mounting of the female 
by the male, and mating. Typically the male is conspicuously 
marked with bright and/or contrasting colors both anteriorly and 
dorsally; the anterior patterns are displayed during courtship. 
Unlike most other species, both males and females of P. mystaceus 
are cryptically-colored gray spiders that live in trees (Specht and 
Dondale, 1960; Warren et al., 1967, as P. incertus; see Edwards, 
1977, for nomenclatorial comments); males have mostly anteriorly- 
oriented modifications (Fig. 5). While anterior modifications are 
probably used by each sex to identify the other (especially the 
female recognizing the male as a conspecific and potential mate) 
from distances of a few centimeters, visual identification at longer 
distances might be severely handicapped by cryptic coloration. A 
mechanism which increases the chance of one sex locating the other 
could be selected for under these circumstances. 
The role of acoustic or vibratory signals in the courtship of P. 
mystaceus may have co-evolved with cryptic coloration. As selec- 
tion for cryptic coloration increased in association with exploitation 
of a new microhabitat (most Phidippus species live in the herb- 
shrub zone), the role of visual communication might have been in 
part supplanted by sound during courtship. The use of sound, 
whether airborne or substrate-borne, would have several advantages 
over conventional visual courtship, if the sound extended the male’s 
communicatory distance from a few centimeters to over a meter (as 
it appears to do based on the audible component available to the 
human ear). Sound is transmitted well through solids, and consider- 
ing that in this case sound is produced on the substrate, vibrations 
through this medium may be most important for female-to-male 
orientation (as Rovner, 1967, showed to be the case for wolf 
spiders). By orienting toward the male upon perception of the 
