522 Dr. F. A. Dixey On the Diaposematic 



greater needs — a rule which holds good not only in 

 mimicry but also in other kinds of defence. Another 

 point worthy of notice is, that as shown by Figs. 6 and 7, 

 compared with 6a and 7a, the resemblance borne to each 

 other by the upper surfaces of the two insects does not 

 extend to the lower. This seems to favour the view that 

 the enemies in this instance guarded against are such as 

 attack butterflies on the wing rather than at rest. 



But the most interesting feature in the case is the 

 evidence it affords of diaposematism, or the interchange of 

 warning characters between mimic and model. In his 

 original description of H. corva, Wallace drew attention to 

 the fact that this form possesses a black border to the 

 hind -wing, " much wider and more defined than in the 

 allied forms" (Trans. Ent. Soc. Lond., 3rd Series, IV, 

 1867, p. 339). This dark border, as can be seen in Plate 

 XXXI, figs. 3-6, is present in both sexes ; it is formed 

 in the female by the fusion of the submarginal row 

 of V-shaped spots seen in Fig. 1 with the actual dark 

 edging of the wing. A somewhat similar feature, though 

 less pronounced, occui's in If. lichcnosa, Moore, from the 

 Andaman Islands; but in the ordinary allied forms known 

 as Htiphina nerissa, H. phryne, H. co])ia, etc., it does not 

 exist. A comparison of Figs. 1 and 2, which represent 

 the female and male respectively of the typical H. fhryne, 

 of continental India, with the figures of H. corva in the 

 same Plate, will show the difference referred to by Wallace. 

 This difference is even better marked in the dry-season 

 form of H. phryne than in the wet, the latter being the 

 phase here figured. 



Now it is in large measure to the presence of this dark 

 border on the hind-wing that H. corva owes its correspond- 

 ence in aspect with /. halicnsis. It is of course open to 

 anyone to assert that the dark border is merely an acci- 

 dental feature in H. corva without any special significance. 

 But when we consider that this feature is practically 

 restricted to that form of the H. nerissa group whose 

 range overlaps that of the Ixias which it so closely re- 

 sembles, the conclusion seems at once to suggest itself 

 that the presence of the dark border in H. corva is the 

 result of a mimetic approach to the other insect. In this 

 respect, then, the Hupliina has acted as the mimic and 

 the Ixias as the model. If, however, we turn to the fore- 

 wing, we find the process reversed; here it is the Ixias 



