165
But when these disappear, other insect-eaters come upon
the scene.
“ The tree-creepers and the tits, insectivorous in their propensities,
are content to seek food in the crevices of bark up and down the
branches of old trees, in the cracks of walls, in and out among the
stones and bricks of old buildings, peering, probing, pecking at
the creatures that have thought to get safely through the cold weather
by hiding.”—{Ibid. p. 164.)
Our winter migrants find in our
“ . . . river estuaries, oozy mudbanks and golden sands, among
other things larvae and all manner of marine insects. . . . Inland
too, we have stores of bird-food in winter. Very seldom indeed is
the ground so hard frozen that the rooks and the thrushes cannot
probe it with their long bills and find here a worm and there a grub,
and there the larva of some bright butterfly.”—{Ibid. p. 163.)
Even in the season when insects fully developed are on
the wing, they are not saved merely by the colours which
they assume.
“ It seems probable, that in some cases, that which would appear
at first to be a source of danger to its possessor may really be a
means of protection. Many showy and weak-flying butterflies have
a very broad expanse of wing. . . . They are often captured with
pierced and broken wings as if they had been seized by birds from
which they had escaped. But if the wings had been smaller in
proportion to the body, it seems probable that the insect would
be more frequently struck or pierced in a vital part.”—(Wallace.
Contributions, p. 33.)
Thus the increased expanse of wing has been a source
of safety which has hindered the action of Natural Selec
tion in its attempt to weed out some of the variants.
So far as the modification of colour is concerned, it may
further be observed that the coloration of the wings assists
in enhancing this immunity from destruction.
“The brilliant colour is so placed as to serve for protection ; as, for
example, the eye-spots on the hind wings of moths which are pierced
by birds, and so save the vital parts of the insect ; while the bright