102 



THE EVOLUTION THEORY 



genus 



Castnia, whose 



B 



but one of the day-flying species of the 



systematic position is doubtful. 



The West African immune Acrgeid, Acrcea gea (PL 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 Xymphalid, Pseudacrcea 

 hirce, by the female of a Papilio 

 A (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 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 greyish-black Acrcea 

 egina, with brick-red spots and bands, 

 and coal-black dots (Fig. 18, A). This 

 immune species is deceptively mimicked 

 in its native country by two other 

 butterflies— a Xymphalid, Pseudacrcea 

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

 Papilio (P. ridleyanus) (Fig. 18, 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 different immune models, for who 



Fig. 18. Upper surfaces of a, Acrcea would have ventured to prophesy how 



egina, from the Gold Coast, immune. f ar t ] ie capac ity of a species for varia- 



B, Papilio ridleyanus. from Gaboon, not . -,.™ 



immune. C, Pseudacrcea buisduvalii, tioil might gO, and llOW many different 



from the Gold Coast, not immune. kinds Qf coloration it was able t O 



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

 in this respect. 



c 



