change in the course of generations. And so the seasonal changes
in the history of the individual from egg to imago point us to changes
in the age-long history of the race.

CHAPTER IX

PAST AND PRESENT; THE MEANING OF THE STORY

In the previous chapter we recognised how the seasonal changes in
various species of butterflies as observable in two or three
generations, indicate changes in the history of the race as it might be
traced through innumerable generations. The endless variety in the form
and habits of insect-larvae and their adaptations to various modes of
life, which have been briefly sketched in this little book, suggest
vaster changes in the class of insects, as a whole, through the long
periods of geological time. Every student of life, influenced by the
teaching of Charles Darwin (1859) and his successors, now regards all
groups of animals from the evolutionary standpoint, and believes that
comparisons of facts of structure and life-history of orders and classes
evidently akin to each other, furnish at least some indications of the
course of development in the greater systematic divisions, even as the
facts of seasonal dimorphism, mentioned in the last chapter, give hints
as to the course of development in those restricted groups that we call
species or varieties. A brief discussion of the main outlines of the
life-story of insects in the wide, evolutionary sense may thus fitly
conclude this book.

In the first place we turn to the 'records' of those rocks, in whose
stratified layers[12] are entombed remains, often fragmentary and
obscure, of the insects of past ages of the earth's history. Compared
with the thousands of extinct types of hard-shelled marine animals, such
as the Mollusca, fossil insects are few, as could only be expected,
seeing that insects are terrestrial and aerial creatures with slight
chance of preservation in sediments formed under water. Yet a number of
insect remains are now known to naturalists, who are, in this
connection, more particularly indebted to the researches of S.H. Scudder
(1885), C. Brongniart (1894), and A. Handlirsch (1906).

[12] See Table of Geological Systems, p. 123.

We are now considering insects from the standpoint of their
life-histories, and the individual life-story of an insect of which we
possess but a few fragments of wings or body, entombed in a rock formed
possibly before the period of the Coal Measures, can only be a matter of
inference.