SOME INSECTS CLASSIFIED. 65 
concerning wings, mouth-parts, and metamorphosis. 
There are, of course, many insects which do not fall 
easily into one of the orders as we have defined them, 
but it must be remembered that no classification of 
living things can be made to include all individuals. 
Some authors make a greater number of orders of 
- Insecta, but the list here given is thought to conform 
to the best usage of writers on natural history. 
Thysanura. These are small wingless insects with 
biting mouth-parts and incomplete metamorphosis. 
The Pseudoneuroptera have two pairs of wings, 
very nearly alike in most cases. Their wings are very 
thin and transparent and closely veined and not 
capable of being folded. The mouth-parts are fitted 
for biting and the metamorphosis is incomplete. 
The Orthoptera commonly have two pairs of wings, 
the under wings being folded like a fan, and protected 
by the outer pair. The jaws are strong and fitted for 
biting, and the metamorphosis is incomplete. 
The Hemiptera, though sometimes wingless, have 
more often two pairs of wings. In some hemiptera the 
outer wings overlap on the back, the overlapping half 
of each wing being thin and membranous, hence the 
name. The mouth-parts are fitted for sucking, being 
prolonged into a beak used for piercing. They have 
incomplete metamorphosis. 
The Neuroptera resemble the pseudoneuroptera in 
wings and mouth-parts and have complete meta- 
morphosis. 
The Coleoptera have hard outer wings called elytra 
which protect the inner, gauzy wings, which are folded 
both lengthwise and crosswise. The mouth-parts are 
fitted for biting and the metamorphosis is complete. 
The Diptera have only two wings. The mouth- 
parts are fitted for sucking and the metamorphosis is 
complete. 
The Lepidoptera have four wings covered with 
scales. The wings do not fold. The mouth is fitted 
