of honey as could be obtained in the same time from the flora of richer regions where competition lessens the rewards of labor.
It is, therefore, necessary that the insect-dependent plants of colder places should have special attractions, and they do. Observations prove that one or more of the three qualities—color, nectar, and fragrance—which attract visitors are naturally increased in Alpine and northern plants, and it is not strange that some insects have been persuaded to leave all and follow these into their colder homes.
McLeod in the Pyrenees, Delpino in Spitzbergen and Nova Zembla, Müller in the Alps, and Verhoeff on the island of Norderney, all concluded that, in correlation with a scarcity of certain classes of insects, the flowers are either more conspicuous, or there is a noticeable increase in number of wind or self fertilized forms.
That climate alone can not account for the lack of beautiful flowers in countries where flower-visitors are rare, is the more evident in the comparison of the weedy flora of Tahiti with the rich one of the neighboring Sandwich Islands, or with that of Juan Fernandez, in both of which honey-sucking birds abound.
Again, there is proof of the actual preference of the different groups of insects and birds for particular kinds and colors of flowers.
The richest and gayest flowers of the world are those of temperate Australia, South Africa, the south European Alps, and South America. Honey-suckers abound in the first (are found nowhere else in the world); most of the sun-birds of the world are found in the second; humming-birds are almost exclusively confined to the last; butterflies and bees characterize the third.
Large, bright-colored, scentless flowers seem to be the favorites of birds and butterflies.
Riley says that "white moths are naturally attracted to white flowers." The difference in color between flowers visited by night-flying moths and by butterflies is very instructive, showing that something more than absence of light has led to the general colorlessness of evening blossoms (compare the day and night-flowering species of lily, etc.), many of which are fragrant, keeping "their sweetness to themselves all day," to "let the delicious secret out" under cover of darkness. So fragrance does the work of the honey-guides which are invariably lacking in evening flowers. Since many of these remain open only a short time—one, two, or three nights—it is the more important that they be easily found by the keen sighted and scented friends, to whom fragrance is as sure a guide as color.
But of all insects, the females of the social bees take the leadership in horticulture. They are the most useful and in-