The geographical distribution of animals, with a study of the relations ...

'chap, x.] THE PALMARCTIC REGION. 211Mr. Wollaston ; that those species which possess wings inMadeira, often have them rather larger than their allies inEurope. These two facts were connected by Mr. Darwin, whosuggested that flying insects are much more exposed to beblown out to sea and lost, than those which do not fly(and Mr-Wollaston had himself supposed that the " stormy atmosphereof Madeira had something to do with the matter) ; so that themost frequent fliers would be continually weeded out, while themore sluggish individuals, who either could not or would notfly, remained to continue the race ;and this process going on fromgeneration to generation, would, on the well-ascertained principlesof selection and abortion by disuse, in time lead to theentire loss of wings by those insects to whom wings were not anecessity. But those whose wings were essential to their existencewould be acted upon in another way.All these must flyto obtain their food or provide for their offspring, and those thatflew best would be best able to battle with thestorms, and keepthemselves safe, and thus those with the longest and mostpowerful wings would be preserved. If however all the individualsof the species were too weak on the wing to resist thestorms, they would soon become extinct. 1Now this explanation of the facts is not only simple andprobable in itself, but it also serves to explain in a remarkablemanner some of the peculiarities and deficiencies of the Madeiraninsect fauna, in harmony with the view (supported by the distributionof the birds and land shells, and in particular by theimmigrant birds and insects of the Azores) that all the insectshave been derived from thecontinent or from other islands, by1A remarkable confirmation of this theory, is furnished in the Report tothe Royal Society of the naturalist to the Kerguelen Island, " Transit Expedition—the Rev. A. E. Eaton. Insects were assiduously collected, and itwas found that almost all were either completely apterous, or had greatlyabbreviated wings. The only moth found, several flies, and numerous beetles,were alike incapable of flight. As this island is subject to violent, andalmost perpetual gales, even in the finest season, the meaning of the extraordinaryloss of wings in almost all the insects, can, in this case, hardly bemisunderstood.