37G 



THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



elaborateness of design, do they make even the 

 faintest approach to a rivalry with these groups 

 of animals. There must therefore be an internal 

 source of coloration, not everywhere present, 

 upon which external influences may react. 



Mr. Wallace, while rejecting the light-theory, 

 brings forward certain principles which he con- 

 siders throw a light upon the phenomena of color 

 in organic Nature. While demurring to the com- 

 mon conclusion that tropical light and heat are 

 the cause of color, he fully recognizes the general 

 fact that " all the more intense and gorgeous 

 tints are manifested by the animal life of the 

 tropics, while in some groups, such as butterflies 

 and birds, there is a marked preponderance of 

 highly-colored species." This phenomenon he 

 ascribes to a variety of causes, some of which 

 yet remain to be discovered. The foremost place 

 is given to the following consideration : " The 

 luxuriant vegetation of the tropics throughout 

 the entire year affords so much concealment that 

 color may there be safely developed to a much 

 greater extent than in climates where the trees 

 are bare in winter, during which season the 

 struggle for existence is most severe, and even 

 the slightest disadvantage may prove fatal." 

 Fully admitting the force of this consideration 

 in the case of birds, we must yet, with all the 

 deference due to so eminent an authority as Mr. 

 Wallace, point out that it can have very little 

 moment as regards insects which during the win- 

 ter are in a dormant condition, as larvae or 

 pupa?, either in the earth, in the trunks of trees, 

 or other localities where neither beauty can be- 

 tray them nor its lack screen them from the pur- 

 suit of any enemy. 



As the first among the causes of coloration he 

 places the need of protection. He points out 

 that browns and other tertiary colors, being most 

 readily produced by " an irregular mixture of 

 many kinds of solar rays, are most likely to 

 occur when the need of protection is slight, or 

 even when it does not exist at all, always sup- 

 posing that bright colors are not in any way use- 

 ful to the species." Hence browns, olives, and 

 other dirty colors, may naturally be expected to 

 predominate. 



Brilliant colors, again, often serve as a sign 

 that their wearer possesses some unpleasant or 

 dangerous property, and hence warn possible 

 enemies to pass on and seek some less nauseous 

 prey. The number of apparently feeble and de- 

 fenseless species which are clad in the most con- 

 spicuous colors, and which are avoided and re- 

 fused by birds, monkeys, spiders, etc., is aston- 



ishing. The present writer, in a paper read 

 before the Entomological Society ("Transactions 

 of the Entomological Society," 187Y, Part III., 

 page 205), has shown that, in a great number of 

 cases at least, the most showy and conspicuous 

 caterpillars feed upon plants either absolutely 

 poisonous or possessing offensive flavors and 

 odors, whence the rejection of such larvae by in- 

 sectivorous animals. Their brilliant coloration is 

 therefore simply a danger-signal. 



The theory of " Sexual Selection," upon which 

 Mr. Darwin lays great weight, Mr. Wallace finds 

 himself unable to accept as in any way an ex- 

 planation of the distribution of color in animals. 

 He remarks that " while male butterflies rival, 

 or even excel, the most gorgeous male birds in 

 bright colors and elegant patterns, there is liter- 

 ally not one particle of evidence that the female 

 is influenced by color, or even that she has any 

 power of choice, while there is much direct evi- 

 dence to the contrary." In the case of the silk- 

 moth Mr. Darwin admits that " the females ap- 

 pear not to evince the least choice in regard to 

 their partners." On the principle of natural 

 selection among a number of rival male butter- 

 flies, " the most vigorous and energetic " will 

 probably be successful, and, as these properties 

 are very generally correlated with intensity of 

 color, natural selection " becomes a preserver and 

 intensifier of color." Very similar is the case 

 among birds. We know that in many species 

 the male displays his colors and ornaments, 

 but, as Mr. Wallace contends, there is a total 

 absence of any evidence that the females admire, 

 or even notice, this display. " The hen, the tur- 

 key, and the peafowl, go on feeding, while the 

 male is displaying his finery, and there is reason 

 to believe that it is his persistency and energy, 

 rather than his beauty, which wins the day." 

 Here, again, vigor and intense vitality seem to be 

 the chief recommendations of the male in the 

 eyes of the female, and these— as is very strik- 

 ingly manifest in the game-cock — appear corre- 

 lated with intense coloration. Mr. Wallace re- 

 sumes : " Evidence collected by Mr. Darwin him- 

 self proves that each bird finds a mate under any 

 circumstances. He gives a number of cases of 

 one of a pair of birds being shot, and of the sur- 

 vivor being always found paired again almost 

 immediately. This is sufficiently explained on 

 the assumption that the destruction of birds by 

 various causes is continually leaving widows and 

 widowers in nearly equal proportions, and thus 

 each one finds a fresh mate ; and it leads to the 

 conclusion that permanently unpaired birds are 



