580 Insects and Flowers 



this there really seems to be no other explanation of flower shape and appear- 

 ance having the same validity as that of adaptation to insect visitors. 



The most effective criticism of this explanation is one against its effective- 

 ness in explaining color, and particularly color-pattern. It is based on the 

 general consensus of belief among zoologists and entomologists concerning 

 the poorness of insect vision. The general character of this vision, with an 

 account of the eye structure, is explained on pp. 30-33 of this book. The 

 fixed short focal distance, the incompleteness and lack of detail incident to a 

 mosaic image, and the lack of accommodation (only partly provided for by 

 the shifting of the peripheral pigment) to varying light intensity, which are 

 admitted conditions of insect vision, make it seem difficult to account for the 

 intricacy in pattern common to many flowers on a basis of adaptation to 

 animal visitors of such poor seeing capacity as insects. 



Experimental evidence touching this criticism is singularly meager when 

 one considers the importance of the subject. If insects can accurately dis- 

 tinguish colors, and at some distance, and can perceive fine and intricate 

 details of color-pattern at very short distance, then the explanation of floral 

 structure and pattern or adaptation to insect visitors has solid foundation 

 for even the amazingly large and varied results which it attempts to explain; 

 if not, it is hard to understand how the explanation is valid (at least in any 

 such all-sufficient degree as commonly held), despite its logical character 

 (in the light of our knowledge of the nearly limitless capacity for modifica- 

 tion of natural selection) and the abundant confirmatory evidence. 



Most of the experimental evidence so far offered is that included in Dar- 

 win's account (" On the Fertilization of Flowers by Insects ") ; in Lubbock's 

 account of his experiments on honey-bees, familiar because of its presentation 

 in his readable book, "Ants, Bees, and Wasps"; and in Plateau's account 

 of his more recent but less familiarly known experiments with various insects, 

 including bees. Both Lubbock and Plateau are investigators ingenious 

 in device, keen in deduction, and of unquestioned scientific honesty. Yet 

 their conclusions are in direct contradiction. Lubbock believes that bees 

 recognize colors at a considerable distance, that they "prefer one color to 

 another, and that blue is distinctly their favorite." Plateau finds that neither 

 the form nor the brilliant colors of flowers seem to have any important attrac- 

 tive role, "as insects visit flowers whose colors and forms are masked by 

 green leaves, as well as continue to visit flowers which have been almost 

 totally denuded of the colored parts"; that insects show no preference or 

 antipathy for different colors which flowers of different varieties of the same 

 or of allied species may show; that flowers concealed by foliage are readily 

 discovered and visited; that insects ordinarily pay no attention to flowers 

 artificially made of colored paper or cloth whether these artifacts are provided 

 or not with honey, while, on the contrary, flowers artificially made of living 



