76 



Stenohothrus curtipennis Scudd, When about to stridalate, these insects place them 

 selves in a nearly horizontal position, with the head a little elevated ; they then raise 

 both hind legs together, the hind tibiae bent back snugly against the femora during the 

 movement, and grate the thighs against the outer surface of the tegmina. The first one 



Fig. 52. — Note of Stenobothrus curtipennis. 



or two movements are frequently noiseless or faint. In sunny weather the notes are 

 produced at the rate of about six a second, are continued from one and a half to two 

 and a half seconds, and when undisturbed are repeated with intermissions of from five to 

 six seconds.; ^When the sky is overcast, the movements are less rapid. 



Gomphocerus sp. " The males of several species of this genus," says Riley, " pro- 

 duce a loud rattling or hissing sound, somewhat resembling the rattle of the large gray 

 rattlesnake, by rubbing the inside of the thighs against the elytra." The reverse resem- 

 blance is indeed so close that I once stooped to search for the stridulator when I heard 

 the warning of a rattlesnake, but fortunately discovered my error in time to withdraw 

 precipitately. In an undetermined species discovered near Georgetown, Colorado, July 

 17, the note sounded like tch, repeated with exceeding rapidity, while the legs moved 

 very quickly over a very short arc ; the repetition was so rapid as to seem like one 

 note, and it lasted from one to two and a half seconds ; it was always fainter at the 

 start and strongest just before the end. 



Bootettix argentatus Brun. Bruner says this insect produces " a sharp stridulating 

 sound," resembling " that produced by some of the Stenobothri." 



Arcyptera gracilis Scudd. This is a very shy insect, but it stridulates more loudly 

 than other^Tryxalinae ; its note can be heard at a distance of fifty feet. It usually makes 

 four notes, but the number is sometimes greater. The first, a quarter of a second in 



Fig. 53. — Note of Arcyptera gracilis. 



length, is duller than the others, and is followed by a pause of a quarter of a second ; 

 the other notes are of the same length, but sharply sounded and follow each other 

 rapidly. 



Arphia sidplmrea (Burm) Stal. This insect sometimes crackles when flying, but 

 undoubtedly the power of doing so is under control. 



Cliimarocfiphala viridifasciafa (DeGeer) Scudd. This insect usually produces a shuflf- 

 ling or rattling sound uniformly during the whole of its undeviating flight ; but the power 

 of making the sound is apparently under control, for it may be frightened into silence. 



Encoptolophus sordidus (Burm). Precisely the same may be said of this species as of 

 the preceding. 



Tropidolophus formosus (Say) Thorn. This crested locust has a short, rather feeble 

 straight flight of about three or four rods in length, the insect rising at once to a height of 

 about six or eight feet from the ground and gradually settling, going with the wind, the 

 distance of its flight being partly determined by the forse of the same. During this flight 

 it makes, as if it were not at all under control, a continuous and regular very subdued 

 clicking sound, like the very rapid but somewhat muffled ticking of a watch. 



