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 1 ." 



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 2 ." 



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 3 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 Pierinae (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, n. pp. 73, 74. On the same subject— "the gay-coloured females of 

 Pieris" {Perrhybris (Hylothrig) 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 uoted that the male of this 

 species does exhibit a mimetic pattern on the under surface. More Letters, n. p. 78. 



2 Letter from Darwin to Wallace, May 5, 1867, More Letters, n. p. 61. 



3 Descent of Man, p. 325. 



