84. THE PERIODICAL CICADA, 
membranes are often mistaken for the true sound organs, but they 
are rather sounding boards, or drums, to increase and transmit the 
sound vibrations induced by the play of the timbals. That they are 
not essential to the production of sound can be shown by slitting 
them or removing them altogether without there being any cessation 
of the note. Much more important modifiers of sound are the semi- 
circular disks projecting from the thorax over the ‘‘mirrors,’’ which, 
if closed artificially or by the insect, deaden the sound very much, 
or if opened or cut off, allow it to escape in greater volume. In sing- 
ing, also, the insect modifies the song notes and their volume by rais- 
ing and lowering the abdomen, thus opening and closing these disks, 
and the act of singing is also accompanied by a sort of trembling of 
the thorax. The position assumed by the male when singing is always 
with the head upward. The abdomen is then elevated and apparently 
inflated, and with the beginning of the sound is slowly brought down 
against the limb, when the note ceases. After a rest of a few seconds 
this operation is repeated. These abdominal movements vary in 
different species of Cicada and determine in a measure the peculiar 
notes of each. 
THE SONG NOTES OF THE PERIODICAL CICADA. 
The song of the different species of cicadas is very distinctive, and 
one familiar with the music of these insects can as readily recognize 
the particular species by its peculiar notes as one knows the different 
birds or mammals by theirs. The general character of the notes of 
the periodical species has been thus described by Dr. G. B. Smith:¢ 
The music or song produced by the myriads of these insects in a warm day from 
about the 25th of May to the middle of June is wonderful. It is not deafening, as 
many describe it; even at its height it does not_interrupt ordinary conversation. It 
seems like an atmosphere of wild, monotonous sound, in which all other sounds float 
with perfect distinctness. After a day or two this music becomes tiresome and dole- 
ful, and to many very disagreeable. To me it was otherwise, and when I heard the 
last note on the 25th of June the melancholy reflection occurred—shall I live to hear 
it again? 
As one approaches a colony of these insects a peculiar roar, not 
unlike the noise of a factory or a distant reaper, falls on the ears, and 
this becomes louder and more intense as one draws nearer, having at 
times to one standing in the midst of a colony a peculiar all-pervading 
and penetrating effect. The individual notes are somewhat obscured 
under these circumstances, but in the lulls the characteristic sounds 
strike the ear, and the peculiarity is never to be forgotten, especially 
the mournful falling note at the conclusion of each effort. Nearly 
all the principal writers on the Cicada, and notably Potter, Smith, 
and Fitch, have attempted to analyze the song note of this insect, 
4 Scientific American, March 22, 1851, 
