266 TRANSFORMATIONS OF INSECTS. 
of the perfect insects. The beetle or perfect insect usually passes 
a short existence. 
There is great diversity amongst the Co/voptera, both as regards 
their anatomy, physiology, development, and the manner in which 
they live. Many appear to be inferior or lower in the insect scale 
than others ; whilst some are so elaborately constructed that they 
must be placed in the most perfect class. The most decided 
anatomical differences, so far as the internal organs are concerned, 
coincide with striking distinctions in the external conformation of 
the insect; and in those beetles whose limbs denote superior 
powers the nervous system is very concentrated ; and it is less so 
in those species the structures of which are more simple. The food 
of the Coleopicra is of all kinds, so, of course, the modifications 
of the structures of the digestive organs are very great. Many 
of the larve are leaf-eaters, and certain kinds do a great deal of 
harm to all sorts of crops and trees. There is much interest 
attached to the early conditions of the Coleoptera, and there is often 
a striking resemblance between the larve of those families, the 
adult forms of which differ in the strongest possible manner. In 
some families of beetles the development of the larve is very 
slight, and they have no legs, so that they look like worms. In 
other families the larvae have structures which are intended to act 
as legs, but they are feebly developed, and locomotion is there- 
fore very imperfect. On the other hand, many larve are born 
so fully formed, that they are very much like the perfect insects, 
and are more or less active in their habits; and, finally, some on 
leaving the egg possess the habits and the methods of movement 
which characterise the perfect forms. They cannot fly, however. 
All these insects, more or less well organised, must undergo their 
principal metamorphosis during the period of rest and quietude 
when they are nymphs. The metamorphoses, the habits, and the 
instincts of many of the Coleoptera are well known, and those of 
a considerable number of species in each of the great groups into 
which these insects may be divided have been carefully studied. 
There are at least twenty families of the Coleoptera which can 
be readily distinguished on account of their members being very 
characteristically formed ; but it is impossible, from what we know 
at present, to collect them into groups, and to distinguish one from 
