THE CANADIAN ENTOMOLOGIST, 85 



THE TONAL APPARATUS OF RANATRA QUADRl DEN- 

 TATA, Stal. 



BV J. R. DE I. A TORRE BUENO, NEW YORK, N. Y. 



In "The Canadian Entomologist" for August, 1903 (*), I called 

 attention to the sounds produced by Ranaira/itsca, Pal. B. Further study 

 has shown me that the bug I then referred to was in reality Ranatra 

 quadridentata, Stal., and that R.fusca is very rare in the north, if, indeed, 

 it occurs at all, the former being the commonest species in the Eastern 

 United States, the latter, on the other hand, being more southern. The 

 notes referred to, therefore, apply to R. quadridentata, Stal. 



Subsequent observation on a larger number of specimens has con- 

 firmed the exactness of my original observation, and I hav'e found that 

 adults as well as nymphs stridulate, and that the sound is produced under 

 water as well as out of it. When in the water, however, the vibrations pro- 

 duce a louder chirp. Since the time this phenomenon was noted, I have 

 consulted a number of papers on the sounds produced by the Heteroptera, 

 but in none of them have I found any data bearing on the stridulation of 

 Ranatra. Indeed, Mr. Kirkaldy, who is one of the most erudite Hemip- 

 terists and has a very perfect knowledge of the literature' of this group, 

 has brought to my attention that this is a heretofore unrecorded faculty in 

 this water-bug. 



The character of the sound and the insect's motions while producing 

 it are substantially as previously described, except for uniniportant 

 individual variations. 



Dissection has revealed the tonal apparatus. It consists essentially 

 of two opposing rasps, one on the coxa near the base, with longitudinal 

 striations, and the other on the inner surface of the cephalic margin of the 

 lateral plate of the coxal cavity, which plate, by its thinness, must act 

 somewhat in the nature of a sounding-board, intensifying the sound and 

 imparting its vibrations to the surrounding medium. The position of the 

 legs, somewhat obliquely held to the axis of the body, brings the coxal 

 rasp against the coxal plate rasp, and the bug's jerky motions of the legs 



*"Notes on ihe Stridulation and Habits of Ranatra fusca. Pal. B," Can. Ent., 

 Vol. XXXV., pp. 235/7. 



