424 POLLINATION OF FLOWERS 



yellow, and that they are much more generally sweet-scented 

 than flowers which bloom during the day. Many are odorous 

 during only a few hours of the twenty-four, just at the time 

 when the special insects which pollinate them are on the wing. 

 A few flowers (purplish, brownish, or greenish colored) are car- 

 rion-scented and attract flies. 



400. Colors of flowers. Flowers which are of any other color 

 than green probably in most cases display their colors to attract 

 insects, or occasionally birds. The principal color of the flower 

 is most frequently due to showy petals ; sometimes, as in the 

 anemone and marsh marigold, it belongs to the sepals ; and not 

 infrequently, as in some cornels (Frontispiece) and Euphorbias 

 (Fig. 318), the involucre is more brilliant and conspicuous than 

 any part of the flower strictly so called. In the willows and 

 chestnuts the stamens are the conspicuous parts. 



Different kinds of insects appear to be especially attracted 

 by different colors. In general, dull yellow, brownish, or dark 

 purple flowers, especially if small, seem to depend largely on 

 the visits of flies. Eed, violet, and blue are the colors by which 

 bees and butterflies are most readily enticed. The power of 

 bees to distinguish colors has been shown by a most interesting 

 set of experiments in which daubs of honey were put on slips 

 of glass laid on separate pieces of paper, each of a different 

 color, and exposed where bees would find them. 1 



It is certain, however, that colors are less important means 

 of attraction than odors from the fact that insects are extremely 

 near-sighted. Butterflies and moths cannot see distinctly at a 

 distance of more than about five feet, bees and wasps at more 

 than two feet, and flies at more than two and a fourth feet. 

 Probably no insects can make out objects clearly more than 

 six feet away. 2 Yet it is quite possible that their attention is 

 attracted by colors at distances greater than those mentioned. 



1 See Lubbock, Flowers, Fruits, and Leaves, Chapter i. On the general 

 subject of colors and odors in relation to insects, see P. Knuth, Handbuch 

 der Bluthenbiologie. 2 See Packard, Text-Book of Entomology, p. 260. 



