But all
the other orders of insects are represented, and many of our
modern genera are fully evolved. The giant insects of the
Coal-forest, with their mixed patriarchal features, have given
place to more definite types. Swarms of dragon-flies, may-flies,
termites (with wings), crickets, and cockroaches, may be gathered
from the preserved remains. The beetles (Coleopters) have come on
the scene in the Triassic, and prospered exceedingly. In some
strata three-fourths of the insects are beetles, and as we find
that many of them are wood-eaters, we are not surprised. Flies
(Dipters) and ants (Hymenopters) also are found, and, although it
is useless to expect to find the intermediate forms of such frail
creatures, the record is of some evolutionary interest. The ants
are all winged. Apparently there is as yet none of the remarkable
division of labour which we find in the ants to-day, and we may
trust that some later period of change may throw light on its
origin.
Just as the growth of the forests--for the Mesozoic vegetation
has formed immense coal-beds in many parts of the world, even in
Yorkshire and Scotland--explains this great development of the
insects, they would in their turn supply a rich diet to the
smaller land animals and flying animals of the time.
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