794 EEPORT— 1893. 



■which secrete a nauseating fluid, supposed to render them unpalatable to birds. In 

 the same districts he found also similarly coloured butterflies, belonging to the 

 family Pierid(e, which so closely resembled the others in shape and markings as to 

 be easily mistaken for them, but which, unprovided with such secreting glands, 

 were unprotected from the attacks of birds. This resemblance, he thought, was 

 brought about by natural selection for the protection of the edible butterflies, 

 through the birds mistaking them for the inedible kinds. Other cases of mimicry 

 among a great variety of insects have since been pointed out, and the theory of 

 protective mimicry has gained many adherents. Among birds, many instances 

 have been adduced. Mr. Wallace has described the extraordinary similarity be- 

 tween birds of very different families, Oriolus bouruensis and Philemo7i moluc- 

 censis, both peculiar to the island of Bouru. Mr. H. 0. Forbes has discovered a 

 similar brown oriole, Oriolus decipiens, as closely imitating the appearance of the 

 Philemon timorlautensis of Timor-laut. A similar instance occurs in Ceram. But 

 Mr. Wallace observes that, while usually the mimicking species is less numerous 

 than tlie mimicked, the contrary appears to be the case in Bouru, and it is difficult 

 to see what advantage has been gained by the mimicry. Now, all the species of 

 Philemoti are remarkably sombre-coloured birds, and the mimicry cannot be on 

 their side. But there are other brown orioles, very closely resembling those 

 named, in other IMoluccan islands, and yet having no resemblance to the Philemon of 

 the same island, as may be seen in the case of the Oriolus phceochromus and 

 Philemon gilolensis from Gilolo. Yet the oriole has adopted the same livery which 

 elsewhere is a perfect mimicry. May it not therefore be that we have," in this 

 group of brown orioles, the original type of the family, undifferentiated ? As they 

 spread east and south we may trace the gradation, through the brown striation of 

 the New Guinea bird, to the brighter, green-tinged form of the West Australian 

 and the green plumage of the Southern Australian, while westward the brilliant 

 yellows of the numerous Indian and African species were developed, and another 

 group, preferring high elevations, passing through the mountain ranges of Java, 

 Sumatra, and Borneo, intensified the aboriginal brown into black, and hence were 

 evolved the deep reds of the various species which culminate in the crimson of 

 Formosa, Oriolus ardens, and the still deeper crimson of O. trailli of the 

 Himalayas. 



It is possible that there may be similarity without mimicry, and, by the five 

 laws of mimicry as laid down by Wallace, very many suggested cases must be 

 eliminated. We all know that it is quite possible to find between species of very 

 different genera extraordinary similarity which is not mimetic. Take, for instance, 

 the remarkable identity of coloration in the case of some of the African species 

 Macronyx and the American Sturnella, or, again, of some of the African Cam- 

 pophaga and the American Agelaus. The outward resemblance occurs in both 

 cases in the red as well as in the yellow-coloured species of all four groups. 

 But we find that the Macronyx of America and the Campophagct of Africa, in 

 acquiring this coloration, have departed widely from the plain colour found in 

 their immediate relatives. If we applied Mr. Scudder's theory on insects, we must 

 imagine that the prototype form has become extinct, while the mimicker has 

 established its position. This is an hypothesis which is easier to suggest than 

 either to prove or to disprove. Similar cases may frequently be found in botany. 

 The strawberry is not indigenous in Japan, but in the mountams there I found a 

 potentilla in fruit which absolutely mimicked the Alpine strawberry in the minutest 

 particulars, in its runners, its blossoms, and fruit ; but the fruit was simply dry 

 pith, supporting the seeds and retaining its colour without shrinking or falling 

 from the stalk for weeks — a remarkable case, we cannot say of unconscious 

 mimicry, but of unconscious resemblance. Mimicry in birds is comparatively rare, 

 and still rarer in mammals, which is not surprising when we consider how small is 

 the total number of the mammalia, and even of birds, compared with the countless 

 species of invertebl-ates. Out of the vast assemblage of insects, with their varied 

 colours and patterns, it would be strange if there were not many cases of accidental 

 resemblance. A strict application of Wallace's five laws would, perhaps, if all the 

 circumstances were knovra, eliminate many accepted instances. 



