INSECT INSTRUMENTALISTS ALLAKD 581 



quavering, continuous, trilling monotone. The little native ground 

 cricket, Mlogryllus verticalis, has a definitely pronounced habit of 

 chirping, the chirps being often rather prolonged and with very 

 brief intermissions, so that only 38 to 40 are produced per minute. 

 It is a marvelous versatility of life that has evolved these varied 

 modes of stridulation, in the one instance by simply slowing down 

 or speeding up the wing strokes in a continuous series, and in the 

 other by sectioning a series into regular or irregular components 

 comprising several wing strokes for each chirp. 



STRIDULATIONS OF THE TREE CRICKETS, SUBFAMILY OECANTHINAE 



The genus Oecanthus Includes a considerable number of species as 

 our morphological classifications have separated them. Unquestion- 

 ably there is much intergrading within the group, however, and some 

 of the forms show close affinities in many features. In the East the 

 snowy tree cricket, Oecanthus niveus, is the only rhythmically chirp- 

 ing form so far as very definite intervals of sound and silence are 

 concerned. In some mysterious manner its chirps are so nicely 

 regulated into unit sections, so to speak, as to comprise a definite 

 number of wing strokes per chirp, as if these were accurately counted. 

 Some have doubted the capacity of these crickets to appreciate 

 rhythm sufficiently to synchronize their chirpings. This, however, 

 appears not one whit more difficult for me to grant than to under- 

 stand how they can measure or count a definite number of strokes for 

 each chirp. Whether or not it is a conscious or unconscious apprecia- 

 tion or measure of time intervals, it is somehow a marvelous adjust- 

 ment of the physiology or psychology to the time relations involved. 

 If each chirp has the rigid pattern of three strokes or four strokes 

 of the scraper over the file vein, this is somewhere, somehow, the 

 basis upon which its synchronous chirpings must be built. 



The narrow-winged tree cricket, O. angustipennis, and Davis's 

 tree cricket, O. exclamationis, are probably not far separated in 

 their lineage, and both have the same irregular mode of intermittent 

 chirps; that is, the chirp may range from 2 to 10 seconds or more 

 in duration. At very high air temperatures, conducive to energetic 

 expression, these chirps appear almost as irregular trills, sectioned 

 from the long, continuous monotone by momentary interruptions at 

 irregular intervals. 



The continuous quavering trill is characteristic of the broad- 

 winged tree cricket, O. latipennis, the black-horned tree cricket, O. 

 nigricornis and its variety, the four-spotted tree cricket, O. nigricomis 

 quadHpunctatus^ and the pine tree cricket, O. pint. 



In the genus Neoxahea the single species N. hijmnctata, known as 

 the two-spotted tree cricket, chirps in the same irregular droning 

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