of a Stridulaling Apparatus in certain Blantidce. 265 



cannot be overcome without tearing and lacerating the 

 skin. Such a mere prickly edge would obviously be 

 useless as a rasp, for, although a scraper could be passed 

 easily enough over it, backwards, the sharp op])Osing 

 points of the prickles Avould prove an insurmountable 

 obstacle to its return in the opposite direction. 



In all the above-named Mantidce, on the contrary, the 

 serrated tegmina fulfil all the conditions of a good rasp, in 

 that the teeth are all erect and blunt- and smooth-pointed, 

 so as to allow a scraper to traverse them equally easily in 

 both directions — forwards as well as backwards. 



I have never doubted that the toothed fore margin of 

 the tegmina in these Mantidca serves in some way or 

 other as a soinid-producing apparatus, and I have else- 

 where* briefly drawn attention to it, and suggested that 

 it might Avork by being scraped across the prominent 

 corresponding nervure of the wings; but I have since 

 seen reason for abandoning this idea, and I now consider 

 that the sounds may more probably be produced by the 

 rubbing of the abdomen against the toothed edge, — a 

 view to which the structure of the tegmina in the female 

 of Gongylus gongylodes — one of the EmpusidcB — lends 

 some support. In this species, in the males, the edge 

 of the tegmina is toothed all along as in all the other 

 species that have come under my notice; but in the 

 females, the marginal field of whose abbreviated tegmina 

 is so greatly dilated for the greater part of its length as 

 to extend far beyond and below the level of the insect's 

 body, and to be, consequently, quite out of reach of it, 

 the teeth only commence to be developed wdiere the 

 marginal field becomes sufficiently narroAV to bring them 

 within reach of the abdomen. With this single apparent 

 exception, the apparatus appears to be equally avcII- 

 developed in the two sexes of all the species in which it 

 has been met with. 



I have not as yet detected any ridge or ridges specially 

 modified to serve as a scraper, nor would such seem to be 

 needed; least of all in the case of the Empusidce, the 

 postero-lateral angles of Avhose abdominal segments are 

 produced into more or less conspicuous foliaceous lobes. 



It will naturally be asked,f " How is it that nobody has 



* P. Z. S. 1878, p. m6. 



f As was done by my distinguished friend Professor Westwood, viheu 

 I nnentiohed these observations to him. 



