INSECT INSTKUMENTALISTS ALLAED 571 



as the tree crickets, Oecanthus latiperinis, O. pini^ 0. niffrlcornis, 

 PhijUoscyrtus pulchelJus^ and Nemohius paliistris. Among the katy- 

 dids, subfamily Copiphorirue, this method of stridulation is the 

 method of the species Neoconocephalus 7'ohustus, N. retusus, N. 

 nebrascensis, N. palustris^ N. triops^ and others. In the case of the 

 katydids all musical pitch or tonality as judged by human ears is 

 absent. The rapidity of the forward strokes in this continuous play 

 of the scraper across the file vein varies greatly, being relatively 

 slow, it would appear from its snappy notes, in the case of the cone- 

 head, N. retusus, but exceedingly fast in the case of N. rohustus, whose 

 notes may have the even, ear-splitting hum or drone of a rapidly 

 revolving saw. To produce this keen, smooth, hum some thousands 

 of forward strokes of the scraper per minute must be made upon the 

 file vein. Few, if any, of our musical insects would seem to move 

 their wings with such frequency as does this big, powerful katydid. 

 At times the writer has wondered if this katydid were the exception 

 to our rule that the forward stroke of the scraper alone produced the 

 sound. Nature always evolves in terms of alj potentialities, and 

 sometimes, perchance, we shall find both backward and forward 

 strokes producing sound, as in the case of most of our own violin 

 music. 



DISCONTINUOUS STRIDULATION : INTERRUPTED CHIRP OR RASP 



An interruption of this continuous habit of stridulation into dis- 

 tinct intervals of silence and sound is a common feature of the 

 insect's behavior in singing. This produces the chirp or interrupted 

 rasp characteristic of a great number of crickets and katydids. The 

 interval of sound may be long or short, regular or irregular; a|l 

 these habits of rhythm actually occur in one cricket or another, and 

 in some of the katydids. It must be remembered that each chirp 

 is the result of several rapid strokes of the scraper upon the file vein. 

 The number of strokes in a chirp may be few or many, constant or 

 variable. If with regular intermissions of silence, we have the 

 markedly rhythmic method of chirping so characteristic of the 

 snowy tree cricket. If the wing strokes are many and inconstant or 

 variable, we have the long-drawn, melancholy sounds of the tree 

 crickets, Oecanthus ancfustipemm and Neoxdbea hipunctata, with no 

 hint of uniformity or measured beat or rhythm. In the height of its 

 singing period in the heat of August the musical musings of the 

 tree cricket, Neoxahea hipunetata^ are of this order, as if a continuous 

 habit of trilling were merely being broken up irregularly by very 

 brief intervals of silence anywhere, at any time. On the other hand, 

 one who has heard the regular, rhythmic, solemn chirpings of the 

 snowy tree cricket, O. niveus, can not but be impressed with the 

 marvelously nice time relations of it ajl. This regularity indicates 



