Mimicry and Sex 293 
in the males alone, and been transmitted to that sex alone. Thus 
I should account in many cases for the greater beauty of the male 
over the female, without the need of the protective principle.” 
The consideration of the facts of mimicry thus led Darwin to the 
conclusion that the female happens to vary in the right manner more 
commonly than the male, while the secondary sexual characters of 
males supported the conviction “that from some unknown cause such 
characters [viz. new characters arising in one sex and transmitted to 
it alone] apparently appear oftener in the male than in the female”.” 
Comparing these conflicting arguments we are led to believe that 
the first is the stronger. Mimicry in the male would be no dis- 
advantage but an advantage, and when it appears would be and is 
taken advantage of by selection. The secondary sexual characters 
of males would be no advantage but a disadvantage to females, and, 
as Wallace thinks, are withheld from this sex by selection. It is 
indeed possible that mimicry has been hindered and often prevented 
from passing to the males by sexual selection. We know that Darwin 
was much impressed® by Thomas Belt’s daring and brilliant suggestion 
that the white patches which exist, although ordinarily concealed, on 
the wings of mimetic males of certain Pzerinae (Dismorphia), have 
been preserved by preferential mating. He supposed this result 
to have been brought about by the females exhibiting a deep-seated 
preference for males that displayed the chief ancestral colour, inherited 
from periods before any mimetic pattern had been evolved in the 
species. But it has always appeared to me that Belt’s deeply interest- 
ing suggestion requires much solid evidence and repeated confirmation 
before it can be accepted as a valid interpretation of the facts. In the 
present state of our knowledge, at any rate of insects and especially 
of Lepidoptera, it is probable that the female is more apt to vary than 
the male and that an important element in the interpretation of 
prevalent female mimicry is provided by this fact. 
In order adequately to discuss the question of mimicry and sex it 
would be necessary to analyse the whole of the facts, so far as they are 
known in butterflies. On the present occasion it is only possible to 
state the inferences which have been drawn from general impressions, 
—inferences which it is believed will be sustained by future inquiry. 
1 More Letters, u. pp. 73, 74. On the same subject—‘‘the gay-coloured females of 
Pieris” [Perrhybris (Mylothris) pyrrha of Brazil], Darwin wrote to Wallace, May 5, 1868, as 
follows: “I believe I quite follow you in believing that the colours are wholly due to 
mimicry; and I further believe that the male is not brilliant from not having received 
through inheritance colour from the female, and from not himself having varied; in short, 
that he has not been influenced by selection.” It should be noted that the male of this 
species does exhibit a mimetic pattern on the under surface. More Letters, 11. p. 78. 
2 Letter from Darwin to Wallace, May 5, 1867, More Letters, 1. p. 61. 
3 Descent of Man, p. 325. 
