t 253 ] 



THE STRIDULATION OF CORIXA. 



BY GEORGE H. CARPENTER, B.SC. 



In the May number of the Irish Naturalist (p. 114), a note 

 by Mrs. Thompson, of Cork, recorded the interesting obser- 

 vation that a small water-bug of the genus Corixa had been 

 heard to produce two distinct sounds. One was of rare occur- 

 rence and resembled the twittering of a bird ; the other, fre- 

 quently heard, was a continuous shrill note, like the chirping 

 of a grasshopper. Mr. E. Saunders, F.L.S., well known as a 

 high authority on the hemiptera, had never heard of the power 

 of these insects to make such sounds. Mrs. Thompson's 

 observation was, therefore, sufficiently noteworthy, though 

 the cause of the stridulation remained doubtful. Mrs. Thomp- 

 son noticed, however, that the singing was accompanied hy a 

 motion of the front pair of legs. 1 



In view of the problem presented, it is with much satisfac- 

 tion that I find that similar sounds have been recently heard 

 by a French naturalist, M. Ch. Bruyant, from a water-bug, 

 Sigara minutissima, of much smaller size than the species of 

 Corixa. He believes these sounds to be caused by the motion 

 of comb-like rows of bristles, situated upon the front feet, 

 across the rostrum or beak of the insect. A translation of his 

 remarks 2 may be of interest. 



"The tarsus of Sigara is formed of a single joint — the pala of authors. 

 It is simpler than that of Corixa. It presents the form of a somewhat irre- 

 gular oval, and carries at its distal extremit} 7 a thick, stiff bristle which 

 a high power shows to be bifid. The lateral anterior edge is armed 

 with a series of strong, equally rigid bristles, usually as many as 

 thirteen or fourteen in C. minutissima ; these bristles appear to be inserted 

 in some hollows of the integument. The lateral posterior edge, on the 

 other hand, has only a few. . . • These strong bristles moved rapidly 

 across the beak produce the stridulation which we have mentioned, a 

 monotonous sound, not metallic, but exactly like that which the teeth 

 of a comb produce by playing on the edge of a thin plate; indeed, the 

 two instruments are present [in Sigara], but they are microscopic." 



But M. Bruyant's paper was specially welcome in affording 



a reference to a similar observation upon some species of 



Corixa, thus confirming Mrs. Thompson's note. This is due to 



a German naturalist, Dr. Schmidt-Schwedt, who records it in 



a chapter on insects contributed to Dr. Zacharias' work on 



1 Mrs. Thompson has, since the publication of her note, told me that 

 the "two appendages" therein mentioned were, doubtless, the front legs. 

 2 Comptes Rendus, vol. cxviii., 1894, p. 299. 



