Sound-production in the Lamellicorn Beetles. 715 



In the CetoniitUe, whose larvae possess a well-developed 

 vocal apparatus almost identical with that of the Rutelida?, 

 the adults of a single genus only are known to stridulate, 

 the genus Iseliioiisojiha, which is peculiar to Australia, New 

 Guinea and adjacent islands. These are solidly-built 

 beetles with hard exteriors and stout legs, and their method 

 of stridulation seems at first sight exactly the same as that 

 of Macraspis, but the parts of the instrument are really 

 reversed. The vibratile ridges are here placed upon the 

 sides of two or three of the abdominal segments, where 

 they form sligiitly-elevated triangular or crescent-shaped 

 areas. The hind femora arc flattened and so articulated 

 as to slide over these ridged surfaces, and upon the inside 

 of each femur is found a series of oblique ridges traversing 

 its whole breadth. The number of species in which this 

 form of organ occurs is small, and, as seems not uncoaimon 

 among beetles, form an isolated musical community in a 

 host of related forms, the rest of which are without this 

 faculty. 



Another of these isolated groups of species is the single 

 known stridulating genus in the enormous assemblage of 

 species comprehensively known as Melolonthidse, and 

 forming the bulk of the entire Lamellicorn series. As 

 already mentioned, the larvas of the Melolonthidse, at 

 least of those common European genera which have been 

 examined, possess a structure in the mouth very similar 

 to that of the larval Scarabaius. One of the common 

 genera of which the instrument was described by Schiodte 

 is Serica, and in this the adult beetle has a stridulating 

 organ borne in a situation which seems to be entirely 

 peculiar to it. The stridulatory plate is formed by the 

 prosteruum which is produced into a kind of thin lip, the 

 inner side of which is exceedingly delicately ridged. This 

 plate is scraped by the edge of the mesosternum v/hich 

 the movement of the thorax slides up and down within 

 the presternum. 



In no other genus of MelolonthidjB has any true stridu- 

 lating organ been found in the perfect state, although it is 

 said that Melolontha and Polypliylla can utter audible 

 sounds, and Landois in his " Thierstimmen " (p. 109) has 

 accounted for these to his satisfaction, considering Melo- 

 lontha to possess a set of " reeds " in its spiracles and 

 Folypliylla to employ the costal vein of the wing as a 

 musical instrument. In the former case the vibratile 



