SCORPIONS, SPIDERS AND CRABS 237 



palps or leg-like feelers, and the jaws ; or between these 

 feelers and the front legs. But the construction is similar 

 in all. In some Spiders the abdomen bears a horny 

 collar, which is toothed, and these teeth, as the abdomen 

 is raised and depressed, scrape against a number of 

 deHcate ridges on the thorax, or " chest," which form a 

 surface recalHng that of a file. The grating of these op- 

 posing surfaces against one another produces shrill rasping 

 or chirping sounds, which, in some cases at any rate, seem 

 to be designed to inform the female of the presence of a 

 suitor. Those who will, may examine this strange instru- 

 ment for themselves if they will take the trouble to seek 

 for it in one of our commonest English Spiders {Steatoda 

 bipunctatd). That it serves as a sexual excitant, or as 

 an aid to mate-hunting, is indicated by the fact that it is 

 found in males only, or in a very rudimentary condition 

 in the female. There is a large Spider in Assam {Chilo- 

 brachys stridulatus) which produces a sound like the 

 drawing of the back of a knife along the edge of a strong 

 comb ; and there are others which, by the friction of 

 the feelers against the jaws, produce sounds like the 

 buzzing of bees. One of the Wolf-spiders {Lycosa kochi) 

 is known as the " purring " or " drumming " Spider from 

 its custom, at mating-time, of rapidly drumming on dead 

 leaves with its feelers. It is a wood-haunting species, 

 and runs hither and thither over the ground as if searching 

 for something, and pausing frequently to " purr." This 

 singular method of producing sound recalls that of the 

 drumming of Woodpeckers on the hollo\. branches of trees, 

 and similarly is produced without any special mechanism. 

 That the Scorpions should possess similar stridulating 

 organs is only what we should expect, having regard to 

 their kinship with the Spiders. In the great Rock- 



