22 ZOOLOGY 
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which is of the utmost value in any system of classification. 
The character of the wings, and the relation of the prothorax 
to the rest of the thorax, are connected with the powers of flight. 
In some sub-orders wings are entirely absent, and in others, 
although they are fully developed, they may be thrown off, as 
in the ants, and in the workers amongst the white ants or 
Termites. The degree of metamorphosis which an insect under- 
goes in passing from the egg to the adult, though possibly a 
good criterion for phyletic relationship, is of less use for 
practical purposes of classification, inasmuch as it assumes the 
life-history of the insect to be known, and this is by no means 
always the case. 
The Insecta are divided into eight orders— 
1. APTERA. 
ORTHOPTERA. 
NEUROPTERA. 
LEPIDOPTERA. 
HEMIPTERA. 
COLEOPTERA. 
DIPTERA. 
HYMENOPTERA. 
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Before considering the subdivisions and characteristics of 
these orders, it will be advisable to obtain an insight into the 
structure and anatomy of some fairly typical insect form, and 
the common cockchafer, J/elolontha vulgaris, one of the Coleop- 
tera, both on account of its size and its frequency, will form a 
convenient type. 
The cockchafer is about # to 1 inch long, and the chief 
divisions of an insect body into head, thorax, and abdomen 
are easily recognised. The head bears a pair of antennae, and 
three pairs of mouth appendages. The antennae differ in the 
two sexes; they consist of ten segments, the first of which is 
known as the scape. In the male the last seven joints, and in 
the female the last six joints, are flattened out into a series of 
plate-like processes, which have given the name Lamellicornia 
to the subdivision of the Coleoptera to which the cockchafer 
belongs. They are much longer and larger in the male than 
in the female, and in both, each lamella bears an enormous 
