ADAPTATION FOR THE SPECIES 135 
while the grasshopper has his ears upon the side of 
his body. 
Everyone who lives in the country, or goes into the 
country in the summertime, is sure to know the hum- 
ming of the so-called locust. It is an unfortunate fact 
that the word locust may have several meanings. It 
is properly applied to one group of the grasshoppers. 
The creature most commonly called a locust is a 
cicada, or harvest fly. When the weather gets quite 
warm the cicada starts his love song. He has two 
long flaps to his vest, and under each flap he has a 
vibrating drum head. This is set shivering by a mus- 
cle on its under side. The female cicada again is 
silent. 
It is among birds that the love song reaches its 
finest development. It may consist simply of a little 
chirp as in the chippy. It may consist of two notes 
of a different pitch repeated steadily, as in the tufted 
titmouse. It may attain considerable variation, as in 
the robin. But in the choir of our best singers, like 
the catbird, thrasher, and mocking bird, there is un- 
ending variation of notes. It seems almost impossible 
to doubt the charming quality of this voice upon the 
mate. It certainly is chiefly confined to the mating 
season, and is indulged in almost entirely by the 
males. This does not mean that a male does not sing 
excepting when he wishes to charm his mate. But 
