INSECT SUCKERS AND BITERS. 
201 
CHAPTER X. 
INSECT SUCKERS AND BITERS WHICH CHANGE 
THEIR COATS BUT NOT THEIR BODIES. 
Yet hark ! how through the peopled air 
The busy murmur glows, 
The insect youth are on the wing, 
Eager to taste the honeyed spring 
And float amid the liquid noon. 
Some lightly o'er the current skim ; 
Some show their gaily gilded trim, 
Quick glancing to the sun. GRAY. 
F any of us were asked the 
question "What is the use of plants?" 
I think there is little doubt that we 
should answer " To make the world 
beautiful, the air pure, and to provide 
food for man and beast." But if the 
same question could be asked of the 
little green aphis clinging on to the 
stem of a rose-tree (see Fig. 69), he 
would know nothing of the beauty 
or the pure air, nor would he think 
of man or beast, but he would pro- 
bably answer that " plants are made 
for plant-lice." And from his point 
of view he would be right, for there is probably not 
a single herb, or shrub, or tree in the world which 
has not its own peculiar insect, sucking the sap and 
