STRIDULATION IN SOME AFRICAN SPIDERS. 21 
under the stimulus of fear or anger, in exactly the same way as 
the Rattlesnake makes use of its rattle. So far as I am aware, 
the only explanation that has been suggested touching the 
function of the snake’s rattle is that it serves as an advertisement 
of the whereabouts of the poisonous reptile, so that it may be 
avoided by enemies which might otherwise inadvertently injure 
it. Similarly poisonous and noxious insects are decked with 
'warning colours, so that they may be readily recognized and 
‘not slain in mistake for harmless or edible species. If this 
| be the true explanation of the so-called warning coloration of 
_ the insects in question, and of the whirring noise made by the 
| Rattlesnake, there seems to be no reason to doubt that the same 
| significance is to be attached to the stridulation emitted by the 
| peculiar organs recently discovered in the great African Spiders 
_and described in the preceding pages. 
