1 62 ORGANIC EVOLUTION 



the flowers for nectar. Most insects eat their fill and 

 then fly away and do not return. It is possible, though, by 

 observation of flowers in nature to determine what kinds 

 of insects are their most frequent visitors. In this manner 

 we can determine that " white flowers are especially visited 

 by small flies ; that flowers which depend upon beetles 

 for fertilization are frequently yellow ; that those which 

 especially bid for the favor of bees and butterflies," the 

 nectar gatherers par excellence, "are usually red, purple, 

 lilac, or blue." 1 



Since the visits of insects are so valuable to plants in 

 securing cross-fertilization, it is easy to see that natural 

 selection would be likely to bring about the bright colora- 

 tion of flowers ; and, as insects of different kinds have 

 different color preferences, the color of any sort of flower 

 is likely to be such as to attract the kind of insect best 

 adapted to secure its cross-fertilization. And, in general, 

 we may say that the observations upon the colors of flowers 

 agree with these conclusions. 



The most assiduous honey gatherers are the bees and 

 the butterflies, and it is interesting to observe that the 

 most highly specialized flowers in the different families of 

 plants are usually red or purple or blue, being thus espe- 

 cially attractive to these insects whose preference is for 

 these same colors. 



Much has been written about other principles in the 

 coloration of blossoms, their original color, the order of 

 development of the several colors, the way in which new 

 colors arise, the parts of the petals upon which these new 

 colors are most likely to appear, the meaning of variega- 



1 Grant Allen, The Colours of Flowers. 



