THE ORIGIN OF SPECIES 



Figure 95. Mimicry of the Monarch But- 

 terfly, Danaus plexippus, below, by the 

 Viceroy, Basilarchus archippus, above. 

 (From Storer and Usinger, "General Zool- 

 ogy," 3rd Ed., McGraw-Hill Book Co., Inc., 

 1957.) 



Campephaga nigra, mimic the drongos, but they are themselves edible. 

 The tit, Pariis niger, resembles the above birds ventrally, but has con- 

 spicuous white markings dorsally. Swynnerton offered a cat specimens of 

 all five species, turned ventral surface up. All were refused. But when the 

 birds were turned dorsal surface up, the cat quicklv took the tit, while 

 still refusing all of the others. 



The Reaction against Protective Coloration. During the Romantic 

 Period, almost every dull color pattern was interpreted as cryptic, almost 

 every brilliant pattern as aposematic, and almost every resemblance be- 

 tween pairs of species as mimicry. This involved many gross errors, much 

 uncritical acceptance of scanty and ill-founded data. In subsequent years, 

 the selective value of color was commonly denied altogether, and was 

 quite generally treated as one of the most doubtful aspects of evolutionary 

 theory. The most important bases of this reaction, in addition to the purely 

 psychological one, were three. First, the vision of predators might be 

 suflBciently different ( based upon ultraviolet hght, for example ) from that 

 of man to invalidate the judgments of human observers. Second, the dis- 

 tastefulness of insects which serve as models for mimics had not been 

 generally proved, and many biologists contended that the distastefulness 

 was not genuine. Finally, McAtee published a study, based upon the 

 examination of the contents of the stomachs of 80,000 birds, in which he 

 reported that both protectively and nonprotectively colored insects were 

 eaten by North American birds in numbers proportional to their respective 

 populations. Because of its very broad experimental basis, this study has 

 had great influence in discrediting the whole idea of adaptive coloration. 

 Thus, in 1936, Shull * was able to write that "if the doctrine ( of natural 



* By permission from Shull, "Evolution," McGraw-Hill Book Co., Inc., 1936. 



246 



