CHAPTER XVII 
THE MOST IMPORTANT CLASSES OF INSECTS 
If we wish to study insects, it is necessary to arrange them 
in groups, for it would be entirely impossible to consider 
separately more than a very small fraction of the various 
species. The classification of insects is based chiefly on 
the number and structure of the wings of the adults, though 
other things are also taken into account. The structure 
of the mouth, for example, is 
quite important because that 
determines the feeding habits of 
the creature. When the mouth 
parts are formed for biting, the 
insect may eat vegetation and 
other solid food, but if they are 
formed for sucking, then it must 
live upon the juices of plants or 
the blood of animals. #\ 
There are many other classes L ao! aval 
of insects besides the six orders Common Rep-reccEp GRASSHOPPER 
which we shall describe here, Sihioapitigy unite ee fe 
but these are the largest, the most important, and the best 
known. We shall pay particular attention to the life history 
of each kind described. o 
Grasshoppers, Katydids, Crickets, and Cockroaches. — 
These have two pairs of wings, the front pair being thickened 
and lying flat upon the insect’s back. The: hind. pair. are. 
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