212 PRINCIPLES AND CONCLUSIONS. 



one a moment later (p. 210) and to rebuke Mueller, Plateau, and others 

 for proving the obvious. He is far from clear as to the practical difference 

 between the distinction of colors and the preference for certain ones, and 

 fails to realize that the marked constancy of many bees indicates that 

 distinction and preference are often the same thing. He apparently did 

 not know the careful work of Mueller as to color preferences for petals, 

 which, like that of Lubbock, is corroborated by the later researches of 

 Lovell, Turner, Frisch, and others. Lovell in particular has shown that 

 green flowers and green objects are visited much less than bright-colored 

 ones and often not at all, and this has been confirmed by Allard in his work 

 with cotton blossoms. The results of Plateau and of Forel with respect 

 to artificial flowers are contradicted by those of Andreae, Wery, Detto, 

 and others, and it is evident that time, place, and other factors often 

 play a controlling part in the behavior of insects to such imitations. Move- 

 over, if insects can distinguish chlorophyllic colors from others in the case 

 of artificial flowers that deceive human vision, it is impossible to believe 

 that they are unable to distinguish the strikingly different forms of various 

 flowers. The evidence for the perception of form by bees is given later, 

 and it is only necessary to point out here that Forel himself speaks of their 

 seeing the dry remains of flowers and the buds of Oenothera. 



Contradictory nature of Plateau's later conclusions. — While several 

 critics have pointed out that Plateau materially modified his earlier state- 

 ments as to the relative r61e of color and odor in attraction, the greater 

 contradictions involved in his later ones have been overlooked. These 

 are contained in the four extracts that follow, which represent the last 

 ten years of his work, 1899 to 1910. 



"I have never said, in my previous studies or the present memoir, that insects do not 

 see the colors of flowers. This assertion would be absurd. But I insist that we have no 

 practical means of assuring ourselves whether there exists a perception of color and 

 whether this is the same as our own. The question to be resolved is this: whatever 

 may be the visual perceptions of insects, are those that visit flowers guided in their choice 

 by the colors that the flowers present to the human eye. The reply can only be negative 

 [1899:368]. I admit fully that the insect can perceive flowers at some distance, 

 whether it be because he sees their colors in the same manner that we do or because 

 he perceives a certain contrast between the flowers and their surroundings, I admit 

 that concurrently with the sense of smell, although to a much less degree, this vague 

 visual perception can guide the animal to the whole floral mass; but once arrived 

 there, if the flowers differ among themselves by color alone, he will prove by his be- 

 havior that it is entirely indifferent to him, as Bulman says, whether the corollas are 

 blue, red, yellow, white, or green" (370). 



As a result of his experiments with bumble-bees deprived of their an- 

 tennae (1902*: 418), Plateau said: 



"The results of A. Forel are thus shown to be accurate; I state it with the satis- 

 faction of having been able to contribute to the demonstration of a scientific truth. 

 However, it is not necessary to draw from this the exaggerated conclusion that the 

 sense of smell plays no part in the attraction of insects by flowers." "What is to be 

 drawn as a conclusion from all this? It is that, if I have been wrong in attributing 

 an exaggerated preponderance to the sense of smell in the relations between insects 

 and flowers, my numerous observations and experiments prove, as Knuth admitted, 

 that the olfactory sense plays a much more important r61e in the search for flowers 

 by insects than has hitherto been admitted. 



