Origin of Species Variorum

Comparison with 1866

four generations swarm over the whole country. Now if a member of one of these persecuted and rare groups were to assume a dress so like that of a well-protected species that it continually deceived the practised eyes of an entomologist, it would often deceive predacious birds and insects, and thus escape entire annihilation. It may almost be said that Mr. Bates has witnessed the process by which the mimickers have come so closely to resemble the mimicked; for he shows that some of the forms of Leptalis, whether these be ranked as species or varieties, which mimic so many other butterflies, vary much. In one district several varieties 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.

Text in this page (from paragraph 2140, sentence 100 to paragraph 2210, sentence 200, word 65) is not present in 1866

four generations swarm over the whole country. Now if a member of one of these persecuted and rare groups were to assume a dress so like that of a well-protected species that it continually deceived the practised eyes of an entomologist, it would often deceive predaceous birds and insects, and thus often escape destruction. Mr. Bates may almost be said to have actually witnessed the process by which the mimickers have come so closely to resemble the mimicked; for he found that some of the forms of Leptalis which mimic so many other butterflies, varied in an extreme degree. In one district several varieties 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 predaceous 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.

Messrs. Wallace and Trimen have likewise described several equally striking cases of imitation in the Lepidoptera of the Malay Archipelago and Africa, and with some other insects. Mr. Wallace has also detected one such case with birds, but we have none with the larger quadrupeds. The much greater frequency of imitation with insects than with other animals, is probably the consequence of their small size; insects cannot defend themselves, excepting indeed the kinds furnished with a sting, and I have never heard of an instance of such kinds mocking other insects, though they are mocked; insects cannot easily escape by flight from the larger animals which prey on them; hence they are reduced, like most weak creatures, to trickery and dissimulation. ↑ ↑

It should be observed that the process of imitation probably never commenced between forms widely dissimilar in colour. But starting with species already somewhat like each other, the closest resemblance, if beneficial, could readily be gained by the above means; and if the imitated form was subsequently and gradually modified through any agency, the imitating form would be led along the same track, and thus be altered to almost any extent, so that it might ultimately assume an appearance or colouring wholly unlike