106 
DARWINISM 
CHAP. 
to whom wings were not absolutely essential escaped a serious 
danger by not using them, and the wings therefore became 
reduced or were completely lost. But when they were essential 
they were enlarged and strengthened, so that the insect could 
battle against the winds and save itself from destruction at 
o 
sea. Many flying insects, not varying fast enough, would be 
destroyed before they could establish themselves, and thus we 
may explain the total absence from Madeira of several whole 
families of winged insects which must have had many oppor¬ 
tunities of reaching the islands. Such are the large groups of 
the tiger-beetles (Cicindelidae), the chafers (Melolonthidse), the 
click-beetles (Elateridse), and many others. 
But the most curious and striking confirmation of this 
portion of Mr. Darwin’s theory is afforded by the case of 
Kerguelen Island. This island was visited by the Transit of 
Venus expedition. It is one of the stormiest places on the 
globe, being subject to almost perpetual gales, while, there 
being no wood, it is almost entirely without shelter. The 
Rev. A. E. Eaton, an experienced entomologist, was naturalist 
to the expedition, and he assiduously collected the few insects 
that were to be found. 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 
thei'e 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 urticse) 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 perma¬ 
nently 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. This bird, the Lagopus scoticus of 
