Stridulating Organs in Cohoptcra. 447 



coxoe backwards and forwards in their sockets. Stridu- 

 lating organs are present in all the species of Hcliocopris 

 which I have had an opportunity of examining ; but I was 

 unable to find them in any species of Catharsius, a genus 

 so closely allied to Hcliocopris that some authors refuse to 

 consider it distinct. Both genera were formerly included 

 in Copris, and though some species of Co2M'is proper have 

 the power of stridulating, the method is not the same as 

 in iflcliocopris. According to Darwin, Copris limaris 

 stridulates by rubbing the abdomen against a very narrow 

 striated ridge situated on the underside of each elytron 

 close to its sutural margin. 



Stridulation in the Rutelid genus Macrasptis has been 

 noticed by Dr. Ohans, -who, in ascribing it to the friction 

 of the hind femora against a number of oblique ridges on 

 the side of the abdomen, appears to have overlooked the 

 fact that the arcuate ridge, situated on the outer part of the 

 upper face of each femur, which rubs against the abdomen 

 is itself transversely and very regularly striated, and con- 

 stitutes the true stridulating file, the widely separated 

 ridges on the abdomen merely serving to act as so many 

 scrapers. The whole apparatus as it occurs in this genus 

 has recently been correctly described by my colleague Mr. 

 G. J. Arrow, who assisted me in examining it. 



Dr. Sharp (" Ent. Mo. Mag." XI, 1874) has fully described 

 the somewhat similar means by which stridulation is pro- 

 duced in certain species of the Cetoniid genus Lomaptera, 

 since associated together by Dr. Gestro in a separate genus 

 to which he has given the name of Iscliioptsoioha. Here the 

 ridges on the abdomen are situated towards the sides, on 

 the second and third segments, a few on the fourth ; they 

 are more regular and very much closer together than in 

 Macraspis, and form the true stridulating areas, the upper 

 surface of the femora which rubs against them being 

 furnished with a number of rather widely separated 

 scraping ridges. 



The little beetles of the family IlcUroccridx also stridu- 

 late by rubbing the hind femora against the fore part of 

 the abdomen. A well-marked ridge lying in the form of 

 a segment of a circle on each side of the first ventral plate 

 acts as the file, being very finely striated in its inner and 

 posterior part, less finely in its outer and anterior part ; 

 while a single very narrow ridge on the upper face of each 

 femur performs the part of a scraper. Schiodte has 



