238 THE COURTSHIP OF ANIMALS 



scorpions of India and Africa the stridulating apparatus 

 lies between the basal segment of the pincers and that 

 of the first pair of legs, and consists of a set of tubercles 

 and a cluster of curved, hair- tipped spines. During 

 moments of excitement the pincers are waved up and 

 down so that the spinules scrape against the tubercles, 

 emitting a rustling sound, which has been compared 

 to that produced by rubbing a stiff tooth-brush with 

 one's finger-nails. In the South African Opisthophthalmus 

 the mechanism differs, consisting of leaf-like hairs placed 

 on the inner surface of the jaws. But since both sexes 

 possess these strange sound-producing mechanisms it 

 has been suggested that their main, if not their only 

 purpose, is to serve as a warning to enemies to keep their 

 distance. Some of the great bird-eating Spiders 

 {Aviculariidce) produce a kind of whistle ; others, sounds 

 like the dropping of shot upon a plate. 



These stridulating contrivances present some curious 

 and puzzling features. In the first place the sounds they 

 produce are never loud to human ears; therein they 

 differ from the shrill piercing sounds produced by like 

 mechanism by the Crickets and Grasshoppers, though 

 even with some of these the notes are, to us, inaudible. 

 In the second, it has been suggested that where both 

 sexes possess a stridulating apparatus its purpose is 

 solely to warn off enemies, and this because the per- 

 formers have no sense of hearing, and are thus, we presume, 

 unaware of the sounds they produce. There is some- 

 thing unsatisfactory about this line of argument. There 

 seems to be no evidence either that the sounds produced 

 are loud enough to terrify an enemy, or that the performers 

 are really deaf. 



In cases where the males alone stridulate it is always 



