^2 THE DESCENT OF MAN 



tators, and the Heliconidse the imitated. Mr. Bates fur- 

 ther observed that the imitating species are comparatively 

 rare, while the imitated abound, and that the two sets live 

 mingled together. From the fact of the Heliconid» being 

 conspicuous and beautiful insects, yet so numerous in indi- 

 viduals and species, he concluded that they must be pro- 

 tected from the attacks of enemies by some secretion or 

 odor; and this conclusion has now been amply confirmed,'" 

 especially by Mr. Belt. Hence Mr. Bates inferred that the 

 butterflies which imitate the protected species have acquired 

 their present marvellously deceptive appearance through va- 

 riation and natural selection, in order to be mistaken for the 

 protected kinds, and thus to escape being devoured. No 

 explanation is here attempted of the brilliant colors :' '■^^ 

 imitated, but only of the imitating butterflies. We musb 

 account for the colors of the former in the same general 

 manner as in the cases previously discussed in this chap- 

 ter. Since the publication of Mr. Bates's paper, similar and 

 equally striking facts have been observed by Mr. Wallace 

 in the Malayan region, by Mr. Trimeii in South Africa, and 

 by Mr. Eiley iu the United States." 



As some writers have felt much difficulty in understand- 

 ing how the first steps in the process of mimicry could have 

 beeu effected through natural selection, it may be well to 

 remark that the process probably commenced long ago, 

 between forms not widely dissimilar in color. In this case 

 even a slight variation would be beneficial, if it rendered 

 the one species more like the other; and afterward the 

 imitated species might be modified to an extreme degree 

 through sexual selection or other means; and if the changes 

 were gradual, the imitators might easily be led along the 

 same track, until they differed to an equally extreme de- 



2» "Proc. Bnt. Soc," Deo. 3, 1866, p. xlv. 



" Wallace, "Transact. Linn. Soc," vol. xxv., 1865, p. i. • also "Transact. 

 i!nt. Soc," vol. iv. (3d series), 1867, p. 301. Trimen, "Linn. Transact.," vol. 

 xxvi., 1869, p. 49'7. Riley, "Third Annual Report on the Noxious Insects of 

 Missouri," 18V1, pp. 163-168. This latter essay is valuable, as Mr. Riley here 

 discusses all objections which have been raised against Mr. Bates's theory. 



