All were incapable of flight, and most of them entirely without
wings. They included a moth, several flies, and numerous beetles. As
these insects could hardly have reached the islands in a wingless state,
even if there were any other known land inhabited by them--which there
is not--we must assume that, like the Madeiran insects, they were
originally winged, and lost their power of flight because its possession
was injurious to them.
It is no doubt due to the same cause that some butterflies on small and
exposed islands have their wings reduced in size, as is strikingly the
case with the small tortoise-shell butterfly (Vanessa urticae)
inhabiting the Isle of Man, which is only about half the size of the
same species in England or Ireland; and Mr. Wollaston notes that Vanessa
callirhoe--a closely allied South European form of our red-admiral
butterfly--is permanently smaller in the small and bare island of Porto
Santo than in the larger and more wooded adjacent island of Madeira.
A very good example of comparatively recent divergence of character, in
accordance with new conditions of life, is afforded by our red grouse.
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