A CHAPTER OF LIFE-HISTORIES. 71 
examination of his ways. Putting him under a tumbler 
over a flower-pot filled with earth, and feeding him 
with bits of apple or potato and sometimes a little 
clover, we may easily observe his movements. If we 
are looking at the male we must watch for the source 
of his cheerful music, for the males do the talking 
among crickets. We shall see, when the shrill sound 
is made, that the outer wings are raised a little and 
Fig. 66.—Female and Male Aphis. 
moved rapidly from side to side. A careful examina- 
tion shows on the inside of the membranous wing-cover 
a vein extending diagonally across the wing and fur- 
nished with teeth like those on the corner of a file. 
On the other wing-cover, near its inner margin, there 
is a hardened part which scrapes over the file, causing 
it to vibrate. The membranes of the wing re-enforce 
the vibration. Thus its voice comes not from its throat 
