40 THOCEEUINOS Ol' THE 



uiul wliicli it is tliernl'ure utlvantagediis to resemble. Such a variety 

 will have a better chance of preservation ; the nulividuals pos- 

 sessing it will be niuhiplieti ; and iheir accidental likeness to 

 the favoured group will be rendered permanent by hereditary 

 transmission, and, each successive variation wincli increases the 

 resemblance being preserved, and all variations departing from 

 the favoured type having less chance of preservation, there will in 

 time result tlio>e lingular cases of two or more isolated and fixed 

 forms bound together by that intimate relationship which consti- 

 tutes them the sexes of a single species. The re;ison why the 

 females are more subject to this kind of modification than the 

 males is, probably, that their slower flight, when laden with eggs, 

 and their exposure to attack while in the act of depositing their 

 eggs upon leaves, render it especially advantageous for them to 

 have some additional protection. This they at once obtain by 

 acquiring a resemblance to other species which, from whatever 

 cause, enjoy a comparative immunity from persecution." 



In the earlier part of this passage Wallace clearly emphasises 

 the role of female variability in the origin of female mimicry in 

 butterflies, and later work tends to emphasise it still further. 

 Considering such a common non-mimetic species as Terias 

 hec'ihe, we Miid the bright eulegnic constant male is associated 

 with a female having didler colours, dyslegnic pattern and much 

 greater variability, furthermore, the study of families with known 

 parents bred by Mr. E. E. Green in Ceylon supports the con- 

 clusion that the degree of variability is hereditary. It is clear 

 that the change to a new pattern would be far more likely to 

 occur in the female of Terias Jiecabe than in the male, and that 

 the particular kind of variability which I have called dys^gnia 

 conduces to sm^h a change. Cluirdxes etheocles affords another 

 example. The females of this species mimic the females and 

 sometimes the mnles of other larger species of Charaxes. I have 

 recently received from S. Nigeria several specimens bred by jNI r, W. 

 A. Lamhorn and by IMr. C. O. Earquharson ; the females of these 

 are non-mimetic and only differ from their males in the possession 

 of an extremely obscure, unstable and highly dyslegnic pattern in 

 paler tints dimly visible on the dark background of the wings — 

 nt.vertheless, slight as it is, the expression of fi male variability. 



Terias hecahe is an example of a species i)i which the sexes are 

 nearly alike ; when we consider those in which they are widely 

 different the origin of female mimicry becomes much clearer. 

 The most striking example known to me was brought to my 

 notice by my friend Mr. S. A. Neave. I refer to the African 

 Nymphaline butterfly. Precis tvestermanni, with an extremely 

 constant male, although the pattern is somewhat dyslegnic, and 

 a female varying in different directions with patterns of several 

 kinds sometimes clearly, sometimes dindy suggested. There are 

 orange-brown forms like the dorip/nis form oi Jhaumla cln-ysippus, 

 orange forms with dark fore-wing markings like Precis sophia, 

 forms with dark fore wings — sometimes again shot with a purplish 



