328 ARACHNIDA-—ARANEAE ‘CHAP. 
chelicera and the inner surface of the femur of the pedipalp were 
finely striated at the point, where they were rubbed together when 
the palps were agitated, but though the appropriate motion was 
frequently given, he could 
hear no sound. 
Meanwhile the noise 
produced by a large Thera- 
phosid spider in Assam 
(Chilobrachys — stridulans) 
had attracted attention, 
and its stridulating appa- 
ratus was described in 1875 
by Wood-Mason.t The 
sound resembled that ob- 
tained by “drawing the 
back of a knife along 
i= the edge of a strong 
Fic. 184. — Chilobrachys stridulans in stridu- comb.” 
re attitude. After Wood-Mason. Natural Subsequently certain 
Sicarid spiders of a genus 
confined’ to the southern hemisphere were heard to produce 
a sound like the buzzing of a bee by the agitation of their 
palps, and both sexes were found to possess a very perfect 
stridulating organ, consisting of a row of short teeth on the 
femur of the pedipalp, and a striated area on the paturon of 
the chelicera. 
Pocock has recently discovered that all the large kinds of 
Theraphosidae in the countries between India and New Zealand 
are, like Chilobrachys, provided with a stridulating organ. In 
these spiders also it is between the palp and the chelicera, and 
consists of a row of teeth or spines constituting a “pecten,’ and 
a series of vibratile spines or “ lyra,’ but whereas in Chilobrachys 
and its near relations the lyra is on the palp and the pecten on 
the paturon, in other spiders the positions are reversed. The 
lyra is a very remarkable organ, consisting of club-shaped, often 
feathery bristles or spines, which he parallel to the surface to 
which they are attached, and which is slightly excavated for 
their reception. 
Lastly, many African Theraphosids possess a similar organ, 
1 Proc. Asiat, Soc. Beng. 1875, p. 197. 
