328 



ARACHNIDA ARANEAE 



Fig. 18-1. — ChUobrachys stridulans in stridu- 

 lating attitude. After Wood-Mason. Natural 

 size. 



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 Ijy a large Thera- 

 phosid spider in Assam 

 ( Chilohrachys stridulans) 

 had attracted attention, 

 and its stridulating appa- 

 ratus was described in 1875 

 by Wood - Mason.^ The 

 sound resembled that ob- 

 tained by " drawing the 

 back of a knife along 

 the edge of a strong 

 comb." 



Subsequently certain 

 Sicariid 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 Chilohrachys, 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 ChUobrachys 

 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 ckib-shaped, often 

 feathery bristles or spines, which lie 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, 



^ Proc. Asiat. Soc. Beng. 1875, p. 197. 



