REHN AND HEBARD 389 



The song of this insect is a very loud and continuous buzzing 

 which is very penetrating and usually audible to a distance of at 

 least 600 feet. This song is given loudly and persistently after 

 dark, rarely lone individuals will be heard singing lustily even on 

 clear days as early as four o'clock. During the day males some- 

 times at long intervals give a short hesitating and irregularh' 

 harsh note which would not be readily associated with their song. 

 Study of material in the field and in captivity as well, was neces- 

 sary to determine the author of this sound, which could often be 

 heard on summer days in the sand grass areas of the New Jersey 

 barrier beaches. This day song, or what might well be termed 

 sleep-song, is in reality a brief and drowsy impulse giving just 

 sufficient energy to the act of stridulation to demonstrate the 

 sound produced when the vibrations are not at full speed, the ir- 

 regularity^ of the sound resulting from the same cause. A species 

 of the genus carefully studied in Jamaica was found to have an 

 even more distinctive note during the day, but due apparently 

 to the identical cause. Other species of the genus will doubtless 

 be found to have similar habits and this, combined with the estab- 

 hshed fact that in certain species of Orthoptera the speed of the 

 normal stridulation varies with the atmospheric warmth, must 

 be remembered in studying the song of various species in different 

 places if confusion is to be avoided. In the sand grass areas of 

 the New Jersey barrier beaches the sound produced at night by 

 myriads of this insect is often astoundingly loud. While stridu- 

 lating the males frequently rest head downward, occasionally 

 moving nervously about without ceasing their song. 



The area of intergradation between typical rohustus and ro- 

 hustus crepitans is very unusually narrow. Large collections of 

 the insect made on the Atlantic coast show that the intergrada- 

 tion takes place in the vicinity of Ocean View, New Jersey, and 

 on the Delaware River in the vicinity of Philadelphia, Pennsyl- 

 vania. On the fall line occasional specimens of such intermediate 

 material is before us from as far south as Washington, District 

 of Columbia. In the large series from elsewhere in the range of 

 rohustus rohustus, the vertex, though showing some variation, 

 is never as blunt as in material from the range of rohustus crepi- 

 tans. There appears to be little or no geographic variation in the 

 range of the present race, though such variation is marked in the 

 very extensive distribution of rohustus crepitans. 



TRANS. AM. ENT. SOC, XL. 



