246 THEORIES OF MIMICRY 



for the facts. If it were valid, the selection would be 

 exerted by the male, for these recent developments are 

 specially characteristic of the other sex. In other cases 

 in which male rather than female selection is supposed to 

 have acted in the production of colour or patterns in 

 butterflies, there is some direct evidence derived from the 

 observation of courtship ; but here no such support is 

 forthcoming 1 . 



Under the theory of Natural Selection the facts at 

 once receive an explanation. Wallace suggested long ago 

 that the slower flight of the females ' 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 pro- 

 tection'. 1 In animals which are hidden bv Protective 

 Resemblance, similar causes explain why the female is so 

 often better concealed than the male. In birds the 

 dangers of incubation balance the dangers of egg-laying 

 in insects. But Protective Resemblances are less special 

 than cases of Mimicry in the sense that the models (bark, 

 twigs, leaves, &c.) are more generally alike throughout 

 all countries, and less rapidly change their distribution 

 than the models of Mimicry and the dominant types of 

 Common Warning Colours. These and other reasons, 

 such as the great number and wide geographical range 

 of species belonging to the same genus and adopting 

 a single method of concealment, compel the belief that 

 examples of Protective Resemblance are extremely an- 

 cient in the past history of the species as compared with 

 examples of Mimicry, so that we can well understand 

 how it is that in the former, when the female differs it is 

 ancestral as compared with its male, while in the latter 

 the converse relationship obtains, and the appearance 

 presented by the male is comparatively ancestral. 



The main conclusion which emerges is that the advan- 

 tageous is the thing that is attained. If an ancestral 

 appearance is advantageous it is retained, especially in 

 the sex that needs it most ; if a new appearance is 



1 Trans. Li>m. Soc, Lo?id., vol. xxv, 1866, p. 22. 



