106 EVENINGS AT THE MICROSCOPE 



in the music by being rubbed against the bows; this, how- 

 ever, seems improbable from their relative position. 



In the Southern United States I have had opportuni- 

 ties of seeing and of hearing a very noisy performer of 

 the Grryllus tribe, called the Katydid (Pterophylla concava), 

 which sings through the night in the foliage of the trees. 

 The sounds, reiterated on every side, resemble a score or 

 two of quarrelsome people with shrill voices, divided into 

 pairs, the individuals of each pair squabbling with each 

 other: "I didl" "You didn't!" "I did!" "You didn't!" 

 the objurgation maintained with the most amusing perti- 

 nacity, and without a moment's intermission. Here the 

 wing-sheaths, which are large and as it were inflated, are 

 certainly the organs of sound. A portion of each is turned, 

 at right angles to the remainder, over the back, so that the 

 one partly overlaps the other. The musical organ consists 

 of a hard glassy ridge in front, behind which is a trans- 

 parent me'mbrane, which appears tightly stretched over a 

 semicircular rim, like the parchment of a drum, answering 

 in structure and in function to the part so compared in the 

 cricket. 



This Gryllus I found would crink freely, when held 

 in my fingers, provided I held it by the head or thorax, 

 so as not to interfere with the freedom of the wing-cases; 

 though these needed only to be partially opened, the bases 

 being merely slightly separated without affecting the gen- 

 eral contiguity. The two glassy ridges were rubbed across 

 each other, making the sharp crink. Ordinarily this was 

 done thrice, three distinct but rapid crossings making the 

 sound represented by the word "Katydid"; but occasion- 

 ally the insect gave but a single impulse, uttering as it 

 were but one syllable of the word. 



