572 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 192 8 



a fundamental treatment of the elements of the chirp, that is, of the 

 forward strokes which produce the component sounds. There is no 

 doubt but that the cricket counts, so to speak, or that at least its 

 physiological mechanism is somehow accurately set to produce just 

 so many strokes in each chirp, otherwise rhythmic regularity could 

 not obtain with the precision this cricket observes so marvelously in 

 all its measured chirping. B. B. Fulton has noted this nice 

 regularity in the case of the chirps of the snowy tree cricket, O. 

 nivevrS. In one Oregon race, which he studied, the number of wing 

 strokes was four ; in another race, according to his observations, only 

 three. It is probable that the wing strokes of this cricket do not 

 often exceed four in each chirp. On the other hand, the wing 

 strokes of the jumping tree cricket, Orochm'ls salfator^ unquestion- 

 ably exceed this number, probably being at least six for each chirp. 



THE SINGLE-STROKE CHIRP OR RASP 



We have considered the long, continuous trill, in which the succes- 

 sive forward strokes of the scraper over the file vein are very rapid, 

 producing in some instances an almost smooth hum or drone of 

 sound. We have seen where this is broken into separate sound in- 

 tervals, each chirp or rasp composed of a number of forward strokes 

 of the scraper, which may be few or many, constant or variable, in 

 their sequences. 



We will now consider a few instances in which the separate chirps 

 or rasps are made by a single stroke of the scraper over the file vein. 

 In reality this is the result of an extreme slowing down of the con- 

 tinuous habit of trilling. It is the most lethargic habit of stridula- 

 tion in this category of methods of using the scraper upon the file 

 vein. The scraper is drawn at comparatively long intervals. It is a 

 most unusual method of stridulation among our true crickets 

 {Gryllidae). In all my studies of this fascinating subject I have 

 found but one cricket which has adopted this single-stroke method 

 of " singing." The musician is one of our tiniest bush crickets, 

 Anaxipha exigua, a species scarcely more than three-sixteenths of an 

 inch in length of body. Its file vein and scraper are of microscopic 

 proportions on its tiny, delicate wings. Naturally the sound struck 

 off is thin and high pitched, one of the highest notes of all our 

 crickets, and almost beyond the range of my own audition, which 

 has been trained to be highly selective and acute with reference to 

 insect sounds. From the smooth, clear character of the almost mi- 

 croscopic sounds of this cricket, so to speak, I have long ago pre- 

 dicted it would be found that each sound ti, in its tinlding song 

 ti-tl-ti-ti-ti is made by a single draw of the scraper over the file vein. 

 This was not definitely established until the summer of 1928. The 



