nr PROTECTIVE RESEMBLANCES AMONG ANIMALS 61 
advantage to other insects to be mistaken for them. There 
is also another extraordinary fact that we are not yet in a 
position clearly to comprehend: some groups of the Heli- 
conidz themselves mimic other groups. Species of Heliconia 
mimic Mechanitis, and every species of Napeogenes mimics 
some other Heliconideous butterfly This would seem to 
indicate that the distasteful secretion is not produced alike 
by all members of the family, and that where it is deficient 
protective imitation comes into play. It is this, perhaps, 
that has caused such a general resemblance among the Heli- 
conide, such a uniformity of type with great diversity of 
colouring, since any aberration causing an insect to cease to 
look like one of the family would inevitably lead to its being 
attacked, wounded, and exterminated, even although it was 
not eatable. 
In other parts of the world an exactly parallel series of 
facts have been observed. The Danaide and the Acreidz of 
the Old World tropics form in fact one great group with the 
Heliconide. They have the same general form, structure, 
and habits; they possess the same protective odour, and are 
equally abundant in individuals, although not so varied in 
colour, blue and white spots on a black ground being the 
most general pattern. The insects which mimic these are 
chiefly Papilios and Diadema, a genus allied to our peacock 
and tortoiseshell butterflies. In tropical Africa there is a 
peculiar group of the genus Danais, characterised by dark- 
brown and bluish-white colours, arranged in bands or stripes. 
One of these, Danais niavius, is exactly imitated both by 
Papilio hippocoon and by Diadema anthedon; another, Danais 
echeria, by Papilio cenea; and in Natal a variety of the 
Danais is found having a white spot at the tip of wings, 
accompanied by a variety of the Papilio bearing a correspond- 
ing white spot. Acrea gea is copied in its very peculiar 
style of coloration by the female of Papilio cynorta, by 
Panopea hirce, and by the female of Elymnias phegea. Acrea 
euryta of Calabar has a female variety of Panopea hirce from 
the same place which exactly copies it ; and Mr. Trimen, in 
his paper on “‘ Mimetic Analogies among African Butterflies,” 
1 A satisfactory explanation of this phenomenon has now been found. See 
Darwinism, p. 252. 
