Origin of Species Variorum

Comparison with 1866

occur, and of these one alone resembles, to a certain extent, the common Ithomia of the same district. In another district there are two or three varieties, one of which is much commoner than the others, and this closely mocks and Ithomia. From many facts of this nature, Mr. Bates concludes that in every case the Leptalis originally varied; and that, when a variety arose which happened to resemble in some degree any common butterfly inhabiting the same district, this variety, from its resemblance to a flourish- ing and little-persecuted kind, had a better chance of escaping destruction from predacious birds and insects, and was consequently oftener preserved;— "the less perfect degrees of resemblance being generation after generation eliminated, and only the others left to propagate their kind." So that here we have an excellent illustration of the principle of natural selection.

Mr. Wallace has recently described several equally striking cases of mimicry in the Lepidoptera of the Malay Archipelago, and other cases could be given with other orders of insects. Mr. Wallace has also given one instance of mimicry amongst birds, but we have no such cases with the larger animals. The much greater frequency of mockery with insects than with other animals, is probably the consequence of their small size; insects cannot defend themselves, excepting indeed the kinds that sting, and I have never heard of an instance of these mocking other insects, though they are mocked: insects cannot escape by flight from the larger animals; hence they are reduced, like most weak creatures, to trickery and dissimulation.

But to return to more ordinary cases of analogical resemblance: as members of distinct classes have often been adapted by successive slight modifications to live under nearly similar circumstances,— to inhabit, for instance, the three elements of land, air, and water,— we

occurred, and of these one alone resembled to a certain extent, the common Ithomia of the same district. In another district there were two or three varieties, one of which was much commoner than the others, and this closely mocked another form of Ithomia. From facts of this nature, Mr. Bates concludes that the Leptalis first varies; and when a variety happens to resemble in some degree any common butterfly inhabiting the same district, this variety, from its resemblance to a flourishing and little-persecuted kind, has a better chance of escaping destruction from predacious birds and insects, and is consequently oftener preserved;— "the less perfect degrees of resemblance being generation after generation eliminated, and only the others left to propagate their kind." So that here we have an excellent illustration of natural selection.

Mr. Wallace has recently described several equally striking cases of mimicry in the Lepidoptera of the Malay Archipelago, and other instances could be given with other orders of insects. Mr. Wallace has also described one case of mimicry amongst birds, but we have no such cases with the larger quadrupeds. The much greater frequency of mimicry with insects than with other animals, is probably the consequence of their small size; insects cannot defend themselves, excepting indeed the kinds that sting, and I have never heard of an instance of these mocking other insects, though they are mocked; insects cannot escape by flight from the larger animals; hence they are reduced, like most weak creatures, to trickery and dissimulation.