In other cases the wingless
Madeira species are distinct from, but closely allied to, winged species
of Europe. The explanation of this change is, that Madeira, like many
oceanic islands in the temperate zone, is much exposed to sudden gales
of wind, and as most of the fertile land is on the coast, insects which
flew much would be very liable to be blown out to sea and lost. Year
after year, therefore, those individuals which had shorter wings, or
which used them least, were preserved; and thus, in time, terrestrial,
wingless, or imperfectly winged races or species have been produced.
That this is the true explanation of this singular fact is proved by
much corroborative evidence. There are some few flower-frequenting
insects in Madeira to whom wings are essential, and in these the wings
are somewhat larger than in the same species on the mainland. We thus
see that there is no general tendency to the abortion of wings in
Madeira, but that it is simply a case of adaptation to new conditions.
Those insects 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.
Pages:
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196