v COLOURS OF ANIMALS 383 
erastus) is coloured so exactly like these that it was at first 
described as a species of Pieris. None of these four groups 
are known to be in any way specially protected, so that the 
resemblance cannot be due to protective mimicry. 
In South America we have far more striking cases, for in 
the three subfamilies Danaine, Acreine, and Heliconiine, all 
of which are specially protected, we find identical tints and 
patterns reproduced, often in the greatest detail, each peculiar 
type of coloration being characteristic of distinct geographical 
subdivisions of the continent. Nine very distinct genera are 
implicated in these parallel changes—Lycorea, Ceratinia, 
Mechanitis, Ithomia, Melinza, Tithorea, Acrea, Heliconius, 
and Eueides, groups of three or four (or even five) of them 
appearing together in the same livery in one district, while 
in an adjoining district most or all of them undergo a simul- 
taneous change of coloration or of marking. Thus in the 
genera Ithomia, Mechanitis, and Heliconius, we have species 
with yellow apical spots in Guiana, all represented by allied 
species with white apical spots in South Brazil. In Mechan- 
itis, Melinzea, and Heliconius, and sometimes in Tithorea, the 
species of the Southern Andes (Bolivia and Peru) are char- 
acterised by an orange and black livery, while those of the 
Northern Andes (New Granada) are almost always orange- 
yellow and black. Other changes of a like nature, which it 
would be tedious to enumerate, but which are very striking 
when specimens are examined, occur in species of the same 
groups inhabiting these same localities, as well as Central 
America and the Antilles. The resemblance thus produced 
between widely different insects is sometimes general, but 
often so close and minute that only a critical examination of 
structure can detect the difference between them. Yet all 
are alike protected by the nauseous secretion which renders 
them unpalatable to birds. 
In another series of genera (Catagramma, Callithea, and 
Agrias), all belonging to the Nymphalidx, we have the most 
vivid blue ground, with broad bands of orange, crimson, or a 
different tint of blue or purple, exactly reproduced in corre- 
sponding, yet unrelated species, occurring in the same locality ; 
1 The above cases have now been satisfactorily explained as a modified 
form of mimicry. See Darwinism, pp. 249-257. 
