STRIDULATION IN 
ACANTHOPHRYNUS CORONATUS (BUTLER) 
(AMBLYPYGI, TARANTULIDAE ) 
By William A. Shear 1 
In April, 1965, during a visit to the vicinity of San Bias, Nayarit, 
Mexico, I collected a living specimen of Acanthophrynus coronatus 
( Butler) , the largest known species of the amblypigid family 
Tarantulidae. The specimen lived in captivity for over a year, 
despite several escapes, and fed voraciously on moths and other 
soft-bodied insects. The usual predatory sequence consisted of re- 
peated light taps on the prey with the whip-like first legs, the left 
and right legs acting alternately, followed by a sudden lunge, too 
quick for the eye to follow in detail, with pedipalps spread wide. 
The prey was caught and impaled on the spines of the pedipalps, 
and tom to bits by alternating movements of the chelicerae. During 
these cheliceral movements, a faint sound could be heard. 
When prodded into its defensive posture, the specimen raised 
its body high off the substrate, spread its palps wide, rocked up and 
down, and rubbed its chelicerae together with reciprocating circular 
movements. A loud, rattling hiss resulted, sounding very much like 
the warning of a small rattlesnake. 
In May, 1966, the specimen molted for the first time in captivity, 
and failed to survive. Upon examination, the newly molted corpse 
proved to be that of a mature male. Recently, I examined the 
specimen in detail. The inner surface of each chelicera (Figs. 1, 2) 
bears a stridulating lyre consisting of a row of short, apically 
expanded spines (Fig. 4) and a plectrum of even heavier spines 
(Fig. 3). There are some differences in the arrangement and 
number of these spines between the right (Fig. 1) and left (Fig. 2) 
chelicerae of the specimen. 
I examined three other males of Acanthophrynus coronatus in the 
collection of the Museum of Comparative Zoology. All had the 
stridulating apparatus, though there were differences in specimens 
from different localities. Figure 5 shows the apparatus of a speci- 
men from San Marcos, Jalisco, Mexico, and Fig. 6 that of a specimen 
department of Biology, Concord College, Athens, W. Va. 24712. Work 
done while supported by a Richmond Fellowship at Harvard University, 
at the Museum of Comparative Zoology. 
Manuscript received by the editor July 15, 1970. 
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