106 MIMICRY, AND OTHER PROTECTIVE 
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 phzochromus, the upper 
surface of which is of exactly the same dark sooty 
tint as the Tropidorhynchus, 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 approxi- 
mation. 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 geo- 
graphy may have led to the restriction of the Tropido- 
rhynchus 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 varia- 
tion 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 Tropidorhynchus - 
(probably some of the hawks), and thus it becomes 
advantageous for the weak Mimeta to resemble the 
