Origin of Species Variorum

Comparison with 1869

to the tricks of the stage? Mr. Bates has, no doubt, hit on the true explanation. The mocked forms, which always abound in numbers, must habitually escape destruction to a large extent, otherwise they could not exist in such swarms; and Mr. Bates never saw them preyed on by birds and certain large insects which attack other butterflies. He has good reason to believe that this immunity is owing to a peculiar and offensive odour which they emit. The mocking forms, on the other hand, that inhabit the same district, are comparatively rare, and belong to rare groups; hence they must suffer habitually from some danger, for otherwise, from the number of eggs laid by all butterflies, they would in three or 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 much 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

to the tricks of the stage? Mr. Bates has, we cannot doubt, hit on the true explanation. The mocked forms, which always abound in numbers, must habitually escape, to a large extent, destruction, otherwise they could not exist in such swarms; and Mr. Bates never saw them preyed on by birds and certain large insects which attack other butterflies; he suspects that this immunity is owing to a peculiar and offensive odour that they emit. The mocking forms, on the other hand, which inhabit the same district, are comparatively rare, and belong to rare groups; hence they must suffer habitually from some danger, for otherwise, from the number of eggs laid by all butterflies, they would, if not persecuted, in three or 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