else live upon other insects, some such provision of food was necessary
for them. Remains of such plants were discovered in the Silurian rocks. In
the Devonian formations, which contain the next oldest set of fossil
insects, numbers of conifers and ferns are found. Yet even then the only
vertebrate animals seem to have been fish. The insects still had the land
all to themselves. Of one of these Devonian insects the base of a wing was
the only part preserved in the rock. From this it was possible to tell the
order to which the creature belonged. It was one of the _Neuroptera_
--insects with wings in which the veins run straight down the wing,
sometimes joined by cross branches at right angles. Some of the modern
kinds are very beautiful four-winged flies, with bright colours on their
wings like butterflies. Others are ant-lions or caddis-flies. The curve of
the fragment of wing also suggested its probable size when unbroken. It
was perhaps two inches long. As there are little horny rings round the
wing base like those which crickets have, on which they rub their legs and
so "chirp," it is also quite likely that this insect of hoary antiquity
did the same, and enlivened the silence of Devonian fern groves with a
prehistoric hum. It is quite in keeping with modern ideas that in that age
of fishes one of the most remarkable insects should have been a kind of
May-fly, "a large species of _Ephemerina_, which must have measured
five inches in expanse of wings." Thus our Thames May-flies had gigantic
prehistoric ancestors, which appeared on earth, possibly with their
present associates the caddis flies, at an enormously remote age.

So far no butterfly had yet appeared on earth, though the
_Ephemerinae_ might dance over the still lagoons and swamps. In the
coal-forest period, and the age of trees and rank vegetation, insects of
many kinds seem to have multiplied, even though the most beautiful of all
were not yet launched in air. In England the first beetle wandered on to
the stage of life--the oldest British insect fossil known. It was