( l^x ) 



I will not venture to offer an opinion. Both forms are 

 inhabitants of the same tropical coast region, and it may well 

 be anticipated that future observation will show their likeness 

 in appearance to have a mimetic significance. I would suggest 

 also that the white form of the female Terias senegalensis, 

 Boisd., which occurs not uncommonly in some parts of Africa, 

 may owe its peculiar aspect to a similar cause. Specimens of this 

 form of the female from the Victoria Nyanza, together with an 

 ordinary yellow male from the same district, are here exhibited. 



" But probably the most remarkable and unmistakable case 

 of mimetic approach to the Nychitona as a model is that 

 afforded by Leuceronia pharis, Boisd., to which I incidentally 

 drew attention in reference to an exhibit recorded in our 

 Proceedings " for 1906, p. xxxi. As I remarked on that occasion, 

 the genus Eronia (including Nepheronia and Leuceronia) has 

 been so strongly affected by mimetic transformation that it can 

 scarcely be said to have an aspect of its own. The male, how- 

 ever, of L. argia, Fabr., is probably as characteristic of the 

 genus as any other form, and a specimen has accordingly been 

 placed by the side of L. pharis, to which it is closely related. 

 Few observers will, it is believed, remain unconvinced that L. 

 pharis represents a departure, of mimetic significance, in the 

 direction of Nychitona. That the latter genus rather than the 

 former has served as the model might be expected from its 

 very wide range and generally uniform characteristics. This 

 is no doubt really the case, but with a qualification. 



"Several years ago I tried to explain certain curious 

 phenomena of mimicry in South American butterflies, by 

 supposing that a mutual interchange of features was liable 

 to take place between distasteful forms — a give-and-take 

 arrangement which I then called ' reciprocal mimicry,' and 

 for which Prof. Poulton has since proposed the more accurate 

 term ' diaposematism ' (Trans. Ent. Soc. Lond., 1894, pp. 

 296-298 • ibid. 1896, pp. 72-75 ; iUd. 1897, pp. 324-331. 

 See also Presidential Address by Mr. Trimen, Proc. Ent. Soc. 

 Lond., 1897, pp. Ixxx, Ixxxi). The principle thus suggested 

 has since been found by Mr. Gr. A. K. Marshall, Prof. Poulton, 

 Mr. Neave and others to be applicable in many other cases than 

 those which first led me to its formulation, and I venture to 



