716 Mr. Gilbert J. Arrow on 



appendages as described by Landois appear to form part 

 of the respiratory system and cannot be supposed to be 

 under the separate control of the insect, so that any sound 

 of Avhich they may be the cause is merely incidental to 

 the function of respiration. Even if Landois is correct, 

 therefore, these structures are not really analogous to 

 those which form the subject of this paper. As to Poly- 

 2ihylla, the beaded appearance of the costal vein is in no 

 way peculiar. It is very commonly found in the wings of 

 Coleoptera, but the rolls are smooth and rounded and 

 seem by no means adapted for producing rapid vibrations. 



The larval instruments of the Dynastidse are practically 

 the same as those of the Rutelidffi, but in the former 

 family a imraber of genera have long been known to have 

 the same faculty in the adult stage. Here again the 

 instruments are foimd in a situation characteristic of the 

 family. The file is borne on the upper-side of the last 

 segment but one of the abdomen and is scraped by the 

 posterior edges of the elytra. The terminal segment is 

 generally uncovered and more or less clothed with hair, 

 but the preceding one is almost covered by the wing-cases 

 in its normal position, and this, in the musical form.s, is 

 bare and transversely striated either across the greater 

 part of its breadth or in narrow longitudinal bands. 



In the Rhinoceros Beetle (Orydes) of Southern Europe 

 and allied forms inhabiting the tropics, such as Stratcgus, 

 Enema, Tricliofiomplius, etc., the sculptured surface is very 

 large, and by the movement of the abdomen can be drawn 

 across a small bent-in piece of the hind margin of each 

 elytron. It was noticed by Darwin that the ridges of this 

 stridulatory plate are finer and more numerous in the 

 female Orydes than in the male, and this to him suggested 

 a difference of function in the two sexes, or perhaps the 

 absence of any function in one. It does not seem to me 

 to be capable of this interpretation. When, as is not 

 uncommon, there is a difference between the two sexes 

 in the fineness of the vibratory ridges, it appears to be 

 the rule that those of the male are coarser than those of 

 the female. If there were a real analogy with the voice 

 of vertebrate animals and of the grasshoppers and loud- 

 voiced in?ects, i.e. if, as Darwin supposed, voice were here 

 as elsewhere primarily a male characteristic, we might 

 expect to find the vocnl apparatus of the female beetle 

 altogether feebler in its development than that of the 



