358 FOUNDATIONS OF BOTANY 
brownish, or dark purple flowers, especially if small, seem 
to depend largely on the visits of flies. Red, 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." 
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.? Yet it is 
quite possible that their attention is attracted by colors at 
distances greater than those mentioned. 
430. Nectar Guides. —In a large number of cases the 
petals of flowers show decided stripes or rows of spots, of 
a color different from that of most of the petal. These 
commonly lead toward the nectaries, and it is possible that 
such markings point out to insect visitors the way to the 
nectaries. Following this course, the insect not only 
secures the nectar which he seeks, but probably leaves 
pollen on the stigma and becomes dusted with new pollen, 
which he carries to another flower. 
431. Facilities for Insect Visits. — Regular polypetalous 
flowers have no special adaptations to make them singly 
1 See Lubbock’s Flowers, Fruits, and Leaves, Chapter I. On the general 
subject of colors and odors in relation to insects, see Miiller’s Fertilization of 
Flowers, Part IV. 
2 See Packard’s Text-Book of Entomology, p. 260. 
