Sound-production in the Lamellicorn Beetles. 737 



these projecting ridges cau be heard to produce a very 

 audible squeaking noise. 



Although Chiasognathus Granti is the only known case 

 of a single species standing alone in a large family as a 

 stridulator and may yet be found to have companions, yet 

 the apparently erratic manner in which stridulating organs 

 are distributed is very remarkable, as is the fact of the 

 much more general possession of the organs by the larva? 

 of the Lamellicornia than by their parents. It is vain to 

 attempt the explanation of these phenomena until we 

 know more about the real significance of stridulation. 

 Dr. Ohaus' observations as to stridulation in beetle com- 

 munities are of the greatest interest, but it would be rash 

 to draw any general conclusions from them, for we are 

 obliged to regard such communities as exceptional, and it 

 is easy to imagine that structures having a quite other 

 primary significance may have become the means of 

 intercommunication in insects whose nervous organization 

 has reached an exceptional degree of development. 



Taking a general survey of the vocal organs here 

 described, the most noticeable feature is the great variety 

 of situation they affect in the Lamellicorn group, at least 

 in the adult stage. Those of the larvae fall into three 

 series, viz, the Lucanid group, in which the stridulating 

 plate is on the hind trochanter, the Geotrupid group (of 

 which the Passalidse exhibit the extreme development), in 

 which it is on the middle coxa, and the Scarabseid group, 

 embracing the great mass of Lamellicornia, where the 

 jaws bear the vocal organs. These larval organs show at 

 least as profound anatomical modifications as any occurring 

 in the mature beetles, and being constant throughout 

 great groups, as we are justified iu supposing them to be, 

 they must be considered more ancient, and therefore of 

 greater significance in classification, than those of the 

 adult insects. 



In the latter the stridulatory file is found at the outer 

 margin of the elytra in Chiasognathus (Lucanidae), on 

 the hind coxae in Geotrupidae, Orphnidae and the genus 

 He/iocojJris in the Copridae, in the corresponding region of 

 the socket in the Taurocerastidae, on the inner margins of 

 the elytra in Trox and Copris, on their lower surface in 

 Ligyrus (Dynastidae) and Ochod^us, — although there is 

 no similarity in the last except in position, the organ 

 in Ligyrus being apparently rather imperfect, while in 



