102 



T]IE EVOLUTION THEORY 



liiit oiu- ol" tlu' (lay-flyiii<j^ species of the genus Castnia, whose 



systematic position is doubtl'nl. 



The West AiVican innnnne Acrajid, Acra'u gea (PL 11, 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, Pseiidacrcea 

 Jdrce, by the female of a Papilio 

 (P. cynorta) whose mate is quite dif- 

 ferent, and by the female of a Satyrid 

 {Elymnias 'phegea) (PI. II, Fig. 20). In 

 the Papilio the resemblance extends to 

 the ^^eculiar 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 greyish-black Acrcea 

 egina, with brick-red spots and bands, 

 and coal-black dots (Fig. t8, A). This 

 immune species is deceptively mimicked 

 in its native country by two other 

 butterflies — a Nymphalid, Pteudacrcea 

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

 Pivpilio (P. ridleyarms) (Fig. iS,B),hy 

 the latter not so exactly as by the 

 former, but quite sufiiciently to be con- 

 fused with its model in flight. 



It would have been less easy to 

 predict with certainty from the theor}'- 

 that, conversely, the difterent species 

 of a genus which stood in need of 

 protection would be able to mimic 

 quite different immune models, for who 

 would have ventured to prophesy how 

 far the capacity of a species for varia- 

 tion might go, and how many ditferent 

 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 otA, Acrcea 

 egina, from the Gold Coast, immune. 

 B, Papilio ridleijanus, from Gaboon, not 

 immune. ('. Pseudacnea boisduvulii, 

 from the Gold Coast, not immune. 



