ADAPTATION FOR THE SPECIES 133 
colored much like the common Leghorns. Shades of 
red and yellow decorate his neck and back, while the 
flight feathers of his wings and of his tail and the 
sickle feathers which ornament the rear of his back 
and hang over his tail are lustrous dark green. The 
hen meanwhile is very much less brilliant in her con- 
trasts. I shall speak more fully of this in discussing 
polygamy. 
The attraction of beauty is not the only lure by 
which a creature may win its mate. Sound may cap- 
tivate as effectively as beauty. This is true of insects 
as well as of birds. Certain insects at least advise 
their mates of their presence by means of a sound 
which they emit. This is particularly noticeable 
among the group of straight-winged insects to which 
the grasshopper, katydid and cricket belong. The 
grasshopper has a ridge on the angle of his wing and 
a roughness on the side of his leg. When these two 
are rubbed together the result is sometimes a fiddling, 
sometimes a snapping or cracking sound, differing in 
different grasshoppers. I doubt not these sounds are 
pleasing to the female of the species, for they are al- 
ways made by the male. The katydid, instead of fid- 
dling in this way, has a sort of drum on the angle 
of his one wing, which he can rub over a tooth in 
the corresponding angle of his other wing, thus pro- 
ducing the familiar “katydid” sound. I have never 
