This section is from the book "Nature's Garden", by Neltje Blanchan. Also available from Amazon: Nature's Garden; An Aid To Knowledge Of Our Wild Flowers And Their Insect Visitors.
"The transition from wind-fertilization to insect-fertilization and the first traces of adaptation to insects, could only be due to the influence of quite short-lipped insects with feebly developed color sense. The most primitive flowers are therefore for the most part simple, widely open, regular, devoid of nectar or with their nectar unconcealed and easily accessible, and greenish, white, or yellow in color. . . . Lcpidoptera, by the thinness, sometimes by the length, of their tongues, were able to produce special modifications. Through their agency were developed flowers with long and narrow tubes, whose colors and time of opening were in relation to the tastes and habits of their visitors." - Hermann Muller
"Of all colors, white is the prevailing one; and of white flowers a considerably larger proportion smell sweetly than of any other color, namely, 14.6per cent.; of red only 8.2 per cent, are odoriferous. The fact of a large proportion of white flowers smelling sweetly may depend in part on those which are fertilized by moths requiring the double aid of con-spicuousness in the dusk and of odor. So great is the economy of Nature, that most flowers which are fertilized by crepuscular or nocturnal insects emit their odor chiefly or exclusively in the evening." - Charles Darwin.