(oe (dix, Ixx 
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 Zerias senegalensis, 
Boisd., which occurs not uncommonly in some parts of Africa, 
may owe its peculiar aspect toa 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 Mychitona 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 Hronia (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 ZL. argia, Fabr., is probably as characteristic of the 
genus as any other form, and a specimen has accordingly been 
placed by the side of LZ. pharis, to which it is closely related. 
Few observers will, it is believed, remain unconvinced that Z. 
pharis represents a departure, of mimetic significance, in the 
direction of Vychitona. 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 ; ibid. 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. G. A. K. Marshall, Prof. Poulton, 
Mr. Neaveand others to be applicable in many other cases than 
those which first led me to its formulation, and I venture to 
think that it may now be taken as a well-established law 
