102 



THE EVOLUTION THEORY 



but one of the day-flying species of the genus Castnia, whose 



systematic position is doubtful. 



The West African immune Acrseid, Acrcea gea (PI. II, Fig. 21), 



is deceptively mimicked, both as to the 

 narrow, long shape of the wing and 

 in its blackish-brown and white mottled 

 markings, by a Nymphalid, Pseudacroea 

 hirce, by the female of a Papiho 

 (P. cynorta) whose mate is quite dif- 

 ferent, and by the female of a Satyrid 

 (Elymnias 2yhegea) (PI. II, Fig. 20). In 

 the Papilio the resemblance extends to 

 the peculiar pitch-black shining spot 

 on the under side of the base of the 

 posterior wing, and all three are like 

 the model on both surfaces, and there- 

 fore in flight as well as in the resting 

 attitude. 



On the same West African coast 

 occurs the strange grej'ish-black Acrcea 

 egina, with brick-red spots and bands, 

 and coal-black dots (Fig. 1 8, A). This 

 immune species is deceptively mimicked 

 in its native country by two other 

 butterflies — a Nymphalid, Paeudacrcea 

 hoisduvalii (Fig. 18, C), and by a female 

 Papilio (P. ridleyanus) (Fig. 1 8, B), by 

 the latter not so exactly as by the 

 former, but quite sufficiently to be con- 

 fused with its model in flight. 



It would have been less easy to 

 predict with certainty from the theory 

 that, conversely, the different species 

 of a genus which stood in need of 

 protection would be able to mimic 

 quite diflferent immune models, for who 

 would have ventured to prophesy how 

 far the capacity of a species for varia- 

 tion might go, and how many different 

 kinds of coloration it was able to 



assume ? But the facts teach us that there is a wide range of possibility 



in this respect. 



Fig. 1 8. Upper surfaces of ^, Acrcua 

 egina, from the Gold Coast, immune. 

 B, Papilio ridleyanus, from Gaboon, not 

 immune. C, Pseudacrcea hoisduvalii, 

 from the Gold Coast, not immune. 



