312 Papers from the Marine Biological Laboratory at Tortugas. 



HISTORY OF THE THEORY OF WARNING COLORATION. 



Darwin, unable to explain by natural selection the conspicuous colors 

 of many animals, suggested the theory of sexual selection, but encountered 

 then a difficulty in certain caterpillars which, though conspicuous, do not 

 show sexual dimorphism. This difficulty he referred to Wallace, who sug- 

 gested (Wallace, 1867) the ingenious theory to which the term " warning 

 coloration " was later applied. The hist(jry of the theory up to the year 

 1887 is to be found in full in Poulton (1887) and need not be here re- 

 peated. It is also to be gathered in part from the later work of Poulton 

 (1890) as well as from Beddard (1802) and Wallace (1891). 



Notable contributions of facts in connection with the theory have since 

 been made by Finn (1895, 1896. 1897, 18970), by Marshall and Poulton 

 (1902), and liy Pritchett (1903). The observations of Finn are of especial 

 importance, since many of them were made on birds at liberty. Originally 

 applied to the immature stages of Lepidoptera. the theory has been ex- 

 tended to imagos of this group and to other groups of insects, notablv 

 to Coleoptera, as well as to various other invertebrate groups. It has 

 now been applied to all the groups of vertebrates. Among mammals the 

 skunk was first instanced by Wallace (1891) and is a classical example. 

 Wallace (1891) and Marshall and Poulton (1902) have cited instances 

 among birds and the latter authors have supported their position by experi- 

 mental evidence. The striking colors of certain poisonous snakes are com- 

 monly cited as examples of warning coloration. Among Amphibia " Mr. 

 Belt's frog" (Belt. 1874, p. 321), and the European Salamandva inaciilata 

 are accorded the places of honor, as striking instances of warning colora- 

 tion. Among fishes Garstang (quoted by Poulton, 1890, p. 165, footnote) 

 has suggested the black dorsal fin of Trachinus z'ipcra as warningly col- 

 ored. Wallace (1891, p. 266) has added certain coral-reef fishes. Hick- 

 son (quoted by Packard, 1904) considers the patches of color about the 

 tail spines of certain surgeon-fishes and similar markings in certain trigger- 

 fishes to be warning in function. Bristol (1903) in a very brief note has 

 suggested a classification of the coloration of coral-reef fish based on its 

 biological significance and has assigned a warning meaning to certain types 

 of coloration. The brevity of Bristol's statement and the absence from it 

 of supporting evidence make it inadvisable to discuss it, but the final 

 paper may well be awaited with great interest. 



ANALYSIS OF THE THEORY OF WARNING COLORATION. 



The observations in support of the theory of warning coloration are so 

 largely confined to the group of insects that the discussion may, for the 

 moment, be conveniently restricted to this group. If we separate from 

 other matter the observations upon which the theory rests they are, I think, 

 accuratelv summarized in the followins: brief statements : 



