Sound-production in the Lamellicorn Beetles. 723 



abdomen against wliicb the coxa revolves is similarly but 

 rather less finely striated. The mobilit}'- of both coxa and 

 abdomen no doubt allows the coxal file, in spite of its small 

 size, to play over the large striated surface in the socket. 

 If a hind coxa is removed from a dead specimen of Hdio- 

 cnpris hucephalus its inner face will be found to be principally 

 clothed with stiff bristles, but these are absent near the 

 margin. The smooth strip remaining is covered with fine 

 but not deep striations, but a very small portion near the 

 inner end is much more deeply and regularly incised and 

 the surface is waved in such a Avay as to produce two or 

 three gentle elevations above the general surface. The 

 microscopic ridges crossing these are exceedingly hard and 

 sharp and are of course rubbed with considerable force 

 against the corresponding abdominal ridges, the effect, as 

 can be easily proved in a dead specimen, being a very 

 audible squeak. In Heliocopris dominus the general stria- 

 tion of the naked part of the coxa, from which the finished 

 instrument has apparently been evolved, has disappeared, 

 but the small perfected portion is practically the same. 



In an allied genus, Synapsis, not hitherto recorded as a 

 stridulator, a similarly sculptured socket occurs, and the 

 inner surface of the coxa is finely corrugated but without 

 any more regularly ridged or elevated spot. Here the 

 bristles have not vanished but are reduced at the inner and 

 posterior part to exceedingly short and stout stumps which 

 lie almost flat and all point forwards. These apparently serve 

 to set up the vibrations, the abdominal ridges here forming 

 a comparatively coarse stridulatory plate. The effect of 

 producing friction between these parts in Synapsis, as might 

 be expected, is a much harsher and less musical sound than 

 in Heliocopris. 



There are three highly peculiar and little known beetles 

 inhabiting the western part of South America and forming 

 the genera Taurocerastes and FricJcius. These have been 

 made by M. Germain into a family under the name of 

 Taurocerastidse, although the points of structure upon 

 which he has relied only point to a relationship with the 

 Orphnidse, with which they have not hitherto been com- 

 pared. None of these insects have hitherto been recorded 

 as stridulators, but I have found organs of several distinct 

 types in the two groups. In Taurocerastes and Frickius 

 (PI. XXXVI, figs. 5, 5a) is a structure similar to that last 

 described, but the striated, or ridged, part of the coxal 



