in PROTECTIVE RESEMBLANCES AMONG ANIMALS 75 



has a very scaly appearance, being covered with rigid pointed 

 feathers which are not imitated in the Mimeta, although there 

 are signs of faint dusky spots which may easily furnish the 

 groundwork of a more exact imitation by the continued 

 survival of favourable variations in the same direction. 

 There is also a large knob at the base of the bill of the 

 Tropidorhynchus which is not at all imitated by the Mimeta. 

 In the island of Morty (north of Gilolo) there exists the 

 Tropidorhynchus fuscicapillus, of a dark sooty brown colour, 

 especially on the head, while the under parts are rather 

 lighter, and the characteristic ruff of the nape is wanting. 

 Now it is curious that in the adjacent island of Gilolo should 

 be found the Mimeta phseochromus, the upper surface of 

 which is of exactly the same dark sooty tint as the Tropido- 

 rhynchus, and is the only known species that is of such a dark 

 colour. The under side is not quite light enough, but it is a 

 good approximation. This Mimeta is a rare bird, and may 

 very probably exist in Morty, though not yet found there ; 

 or, on the other hand, recent changes in physical geography 

 may have led to the restriction of the Tropidorhynchus to 

 that island, where it is very common. 



Here, then, we have two cases of perfect mimicry and two 

 others of good approximation, occurring between species of 

 the same two genera of birds ; and in three of these cases the 

 pairs that resemble each other are found together in the same 

 island, and to which they are peculiar. In all these cases the 

 Tropidorhynchus is rather larger than the Mimeta, but the 

 difference is not beyond the limits of variation in species, and 

 the two genera are somewhat alike in form and proportion. 

 There are, no doubt, some special enemies by which many 

 small birds are attacked, but which are afraid of the Tropido- 

 rhynchus (probably some of the hawks), and thus it becomes 

 advantageous for the weak Mimeta to resemble the strong, 

 pugnacious, noisy, and very abundant Tropidorhynchus. 



My friend, Mr. Osbert Salvin, has given me another in- 

 teresting case of bird mimicry. In the neighbourhood of Rio 

 Janeiro is found an insect-eating hawk (Harpagus diodon), 

 and in the same district a bird-eating hawk (Accipiter pileatus) 

 which closely resembles it. Both are of the same ashy tint 

 beneath, with the thighs and under wing -coverts reddish 



