Sound-production in the Lamdlicorn Beetles. 711 



peep-red colour produced by the dense deposit of cliitin. 

 This characteristic coloration frequently reveals to the eye 

 the presence of organs so delicately proportioned as to 

 require a high power of the microscope to reveal their form. 

 In soft-bodied and pale-coloured larvae in particular their 

 presence may generally be detected in this way. 



The only other requisites in these instruments are that 

 the ridges or spines should have space in which to vibrate 

 without hindrance and should be protected from the risk 

 of injury. An entirely external situation exposes such a 

 delicate structure to wear and tear and clogging by dirt, 

 and is only occasionally found. The sound-emitting 

 surface more commonly occupies a position where it is 

 covered when not in use but is extruded by the act of 

 using it. 



Stridulation is apparently general in the larvae of most of 

 the groups of Lamellicorns, although those of a few of these 

 groups are still unknown. Vocal structures have been 

 described by Schiodte in the earlier stage of many genera 

 dumb in their adult condition, but the only one examined by 

 hitn in which such organs were not found is the genus Trox, 

 the imago of which has long been known to squeak loudly. 

 It is remarkable that whenever the organs are present in 

 both stages, those of the perfect insect are not developed 

 from their larval representatives but invariably occur in 

 an entirely different situation. In the larvae of most of 

 the families the stridulatory area occupies a roughened 

 surface on the lower face of each mandible, so situated 

 as to be capable of being scraped by a series of strong 

 teeth upon the contiguous upper side of the maxilla. In 

 Searabxus the mandibular part of the apparatus is a large 

 space at the base of the jaw thickly covered with minute 

 tubercles, and a row of strong curved hooks is found on 

 the basal part of the maxilla. In the fully-developed 

 beetles no vocal apparatus has been found, although it 

 was long ago reported by a French traveller, quoted by 

 Darwin in " The Descent of Man " (Chap. X), that the 

 male of Searahmus {Atetichus) cicatricosus stridulates to 

 encourage the female in the work of making and rolling 

 the ball of food material, and from distress if she is taken 

 away. I have made a careful dissection of the beetle to 

 find the means by which this is done, but have entirely 

 failed to find any structure adapted for producing sound, 

 and, in the absence of any confirmation of a statement 



