ON INSECT SOUNDS 237 



J^f of an inch, and found it be i milimeter. He then counted 

 the number of notches and found them to be 364, and finally 

 determined the rate of movement of the sharp edge on its antepectus 

 to be equal to 0.17 second. Thus, by formula, he calculated the 



number of separate beats ^ =2iAi=the vibrations of the 



0.17 



musical note d"". 



When [the beetle worked his instrument faster or slower, the 

 tone was raised or lowered accordingly. 



The female of the same species had a notched ridge of ijmm. 

 in length, and on this were counted 304 notches, or 202*6 for 

 I mm. Taking the time as before ascertained at o' 1 7 second, we 



have ■:^^— ^=1783 corresponding to the vibrations of the note a'". 

 0-17 



Professor Landois remarks that every one may distinguish the note 



of the male as higher than that of the female. 



The length of the notched ridge of Ceramhjx heros is 3*4 mm,, 



and the number of notches on it 238, that is 70 to the mm. The 



time was measured at 0*32 seconds. This insect's note is therefore 



~ = 7J.4, which number corresponds to the tone f". Even 



0-32 



for the very^smallest Cerambyx, whose note is too weak or too high 



for the human ear to hear, the tone may be calculated. For 



instance, the notched ridge of *' Gracilia pygmcca '' measures 



0*375 "^"^- ^'^ length, and the number of notches 113, (therefore 



301 to the mm.), the time occupied in friction was o'o8. Hence 



— — = 1413, which corresponds to the tone f". The same formula 

 "oo 



gives some idea of the notes of insects whose fossil remains still 



show the length of the notched ridges and number of notches 



thereon, if we assume the movement of the parts to have the same 



rapidity as is observed in living species. 



2. Tones produced hy motion of the wings of insects. 



Many insects move their wings slowly in flight, e.g, the cabbage 



