Sound-'produdion in the Lamdlicorn Beetles. 713 



mandible a high-pitched note is produced which is only 

 audible to the human ear at a short distance from it. 

 Dr. Ohaus found that when held in the fingers a gentle 

 squeeze caused his larvoe to squeak, but he also found that 

 if a strange larva were introduced into a piece of wood in 

 which others were tunnelling, these would utter a warn- 

 ing cry and the intruder would shortly make his exit 

 again, whereas in an unoccupied log he would readily 

 establish himself. When confined together they showed 

 no compunction in killing and eating each other, so that it 

 is evidently a part of their moral code that each should be 

 left in undisturbed isolation, and if, as is Hkely, their note 

 is conducted undiminished through the wood in which they 

 live, this may supply us with the principal object of the 

 faculty. It is at least probable that when, in the course of 

 tunnelling through the same stump, tw^o burrows approach 

 one another, the warning sound informs the inmates of the 

 position of affairs in time to change their direction. All 

 their operations are, of course, conducted in darkness, so 

 that sight is of no avail to them. The great Danish 

 authority on beetle larvae states that these, in common 

 with Lamellicorn larvae in general, are without eyes, the 

 genus Trox being the only exception known to him ; but 

 I have found a pair of small ocelli, situated just behind 

 the antennae, in ^lao'aqns and other genera^ of both 

 Rutelidas and Dynastidae. 



Dr. Ohaus has been the discoverer of the vocal apparatus 

 in the mature form of the same germs. The beetle draws 

 its hind-legs across its sides as if playing the fiddle, as 

 indeed it does, but the leg represents, not the bow, but 

 the instrument itself, while the abdomen bears the means 

 by which the vibration is set up. If a hind-leg is removed 

 from a dead specimen and the inner face of the femur 

 examined under a lens, it is seen that near the knee and 

 running parallel to the upper edge there is an elevated 

 ridge with a surface like that of a file, owing to a large 

 number of exceedingly fine transverse ridges. Upon that 

 part of the side of the abdomen over which the femur is 

 adapted to move may be found a series of conspicuous 

 ridges which look as if the surface when in a soft con- 

 dition had been deeply scratched in an oblique direction, 

 leaving the upper edge of each cut protruding. These 

 edges form the plectra. Dr. Ohaus states that the beetle 

 sometimes uses this instrument by rubbing the legs across 



