330 Records of the S.A. Museum 



cation is so marked that flu- inscds appear almost iiiiit'ormly dull black' above ; 

 the wiiig'-covers are semi-t i'aiis|)areii1 , and the dai'k api)earaiice is larfrely due 1o 

 tile lliyreseeiit upper-sui'faee of the ahdomeji. jet bhiek in mature adults. Soinc- 

 limes tlu' whole underside. ijieludin<i' the coxae, is black, only tiu' face and otiier 

 log-joints being yellow. 



There seems to be little doubt that the ab(U)minal attachments referi-ed to 

 constitute a stridulatory apparatus. There are two hard, chitinous parts, a 

 movable agent or stridnlatoi-, and a ])assive toothed area Avhich is fixed to the 

 sixth segment. The base of the stridnlatoi- is much expanded and flattened, 

 forming a large lateral lolie. This is attached to the membrane beneatii the tiflh 

 seirment, which more or less covers the lobe, but is not connected witii it. The 

 fi'ee portion is almost straight, sub-cylindrical, and rounded apically; the right 

 side is somewhat tiattened and furnished with long, blunt, and slightly curved 

 pegs, as is also the sub-circular stridulatory area immediately opposite; in the 

 figure both surfaces are shown tui-ned a little towards the observer. 



It is not yet known, whether these parts are operated while the insect is 

 submerged or only when the wings are spread. 



The smaller measurement of the female ( ()"2 mm.) is that given by Kirkaldy ; 

 the specimens examined liy him may have included I)oth sexes, lint the male may 

 not have been recognized, as the ventral segments of the abdomen differ but 

 slightly. 



