CHAPTER VII 
How INSEcTS ARE CLASSIFIED 
More than 350,000 distinct species of insects have been described. 
In addition at least as many more remain to be studied and classified. 
Obviously, in all this array, there must be certain groups that have 
Fic. 18.—A typical specimen of the order Orthop- 
tera. Original. 
many characters in 
common, or give 
indication that at 
some period in the 
remote past they 
were derived from 
common ancestors. 
These groups are 
known as Orders. 
There are more 
than twenty recog- 
nized orders of in- 
sects, but the great 
majority of injurious 
species are included 
in ten principal eco- 
nomic orders. The 
leading characteris- 
tics distinguishing 
these from one an- 
other are the type of metamorphosis, the kind of mouth parts, the 
number, shape, and texture of the wings, the presence or absence 
of compound eyes, the type of antenna, and the shape of the body. 
The ten principal orders and their characteristics are as follows: 
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