INSECTS. 367 



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 marvelously deceptive appearance through 

 variation 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 of 

 the imitated, but only of the imitating butterflies. We 

 must account for the colors of the former in the same gen- 

 eral manner as in the cases previously discussed in this 

 chapter. Since the publication of Mr. Bates' paper similar 

 and equally striking facts have been observed by Mr. Wal- 

 lace in the Malayan region, by Mr. Trimen in S. Africa, 

 and by Mr. Riley in the United States, f 



As some writers have felt much difficulty in understand- 

 ing how the first steps in the process of mimicry could 

 have been 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 degree 

 from their original condition; and they would thus ulti- 

 mately assume an appearance or coloring wholly unlike 

 that of the other members of the group to which they 

 belonged. It should also be remembered that many species 

 of Lepidoptera are liable to considerable and abrupt varia- 

 tions in color. A few instances have been given in this 

 chapter; and many more may be found in the papers of 

 Mr. Bates and Mr. Wallace. 



*"Proc. Ent. Soc.," Dec. 3, 1866, p. 45. 



f Wallace, "Transact. Linn. Soc.," vol. xxv, 1865, p. 1; also 

 "Transact. Ent. Soc.," vol. iv (3d series), 1867, p. 301. Trimen, 

 "Linn. Transact.," vol. xxvi, 1869, p. 497. Riley, "Third Annual 

 Report on the Noxious Insects of Missouri," 1871, pp. 163-168. This 

 latter essay is valuable, as Mr. Riley here discusses all the objections 

 which have been raised against Mr. Bates' theory. 



