74 CENTIPEDES— SPIDEES. 



I may refer to Landois's interesting work, " Thier- 

 stimmen." 



From the fact that the power of producing sounds 

 audible to us is scattered among so many groups, and 

 that the sounds themselves are often so shrill, I am 

 disposed to suspect that many insects usually regarded 

 as dumb really produce sounds, which, however, are 

 beyond our range of hearing. 



Among centipedes Gerstacker has described* a 

 sound-producing organ in Eucoryhar crotijlus. The 

 posterior legs have the fourth segment much enlarged 

 and leaf-like, with the edges raised and formed of 

 very hard chitine. The legs are rubbed against one 

 another, and thus produce a rasping sound. Bourne 

 also has recently described f a stridulating organ in 

 another genus (Sphaerotherium). It is situated just 

 behind the tw^enty-first pair of legs, and consists of a 

 hood-like process bearing a number of parallel ridges. 



There is a very general impression that spiders hear 

 well, and even enjoy music ! There seems, however, 

 very little evidence of any value on the subject. No 

 doubt they are extremely sensitive to vibrations. The 

 presence of even a very small insect on their web is 

 at once perceived. Mr. Boys has shown that the 

 vibrations of a tuning-fork affect them strongly. J 

 This sensitiveness to vibrations is, however, not neces- 

 sarily the same as a true sense of hearing. Kraepelin 

 says § that he knows only one observation which seems 

 to him to possess sufficient exactness to justify the 

 conclusion that spiders possess any sense of hearing — 

 namely, that of Lehmann. 



* Gerstacker, " Stettin Ent. ZeiL, 1854. 



t Bourne, Linnean Journal, 1885. % Nature, vol. xxiii. 



§ " Ueber die Geruchsorgane der Gliederthiere." 



