106 THE INSECT WORLD. 
children think they see a little mirror of the thinnest and most 
transparent glass, or that a little blade of the most beautiful tale is 
set in the bottom of each of these little cells. That which one might 
see if this were the case would in no way differ from what one 
actually sees; the membrane which is stretched out at the bottom 
of the cells does not yield in transparency either to glass or 
to tale; and if one looks at it obliquely, one sees in it all the 
beautiful colours of the rainbow. It seems as if the Cicada has 
two glazed windows through which one can see into the interior of 
its body.” 3 
The horny triangle of which we spoke above only separates in 
two the lower part of the cavity. The upper part is filled by a 
white, thin, but strong membrane. ‘This membrane is only drawn 
tight, when the body of the Cicada is raised. But with all this, 
where is the organ of song? What parts produce the sound? 
Réaumur will enlighten us on this point. 
He opened the back of a Cicada, and laid bare the portion of the 
interior which corresponds with the cavity where the mirrors are, 
and was immediately struck with the size of the two muscles which 
meet and are attached to the back of the horny triangle, and to 
that one of its angles from which start the sides which form the 
cavities in which are both the mirrors. 
“‘ Muscles of such strength, placed in the belly of the Cicada, and 
in that part of the belly in which they are found, seem to be only 
so placed in order that they may move quickly, backwards and 
forwards, those parts which, being set in motion, produce the noise 
or song. And indeed, whilst I was examining one of these 
muscles, in moving it about gently with a pin, slightly displacing 
it, and then letting it return to its proper place, it so happened 
that I made a Cicada that had been dead for many months sing. 
The song, as might be expected, was not loud; but it was strong 
enough to lead me on to the discovery of the part to which it was 
due. J had only to follow the muscle I had been moving, to 
search for the part on which it abutted.” 
In the large cavity in which are the mirrors and the other parts 
mentioned above, there are besides two equal and similar com- 
partments, two cells in which are placed the instrument of sound. 
This is a membrane in the shape of a kettle-drum, not smooth, 
