Page:Popular Science Monthly Volume 25.djvu/348

336 of autumn, in the same plant. It would be impossible to go fully here into the evidence which might be offered on this head; an immense mass of facts shows us that color is always tending to appear in the leaves which immediately surround the floral organs; and that this tendency has been strengthened by insect selection of the most conspicuous blossoms, until it has finally resulted in the brilliant corollas of such flowers as those which we now cultivate in our modern gardens.

But all this takes for granted the very fact with which we are now concerned, the existence and growth of an insect color-sense. How do we know that insects can distinguish colors at all? For otherwise all this argument must be fallacious, and the presence of bright corollas must be due to some other cause.

Of all insects, bees are the most confirmed flower-haunters, and they have undergone the greatest modification in relation to their visits in search of honey. We might expect, therefore, that bees would exhibit a distinct color-sense; and this is actually the case. Sir John Lubbock's experiments clearly prove that bees possess the power of distinguishing between red, blue, green, and yellow. Being anxious to see whether insects were really attracted by the hues of flowers, he placed slips of glass, smeared with honey, on paper of various colors; and the bees upon which he experimented soon learned to return to one particular color only, even though both the paper and the honey were occasionally transposed. Thus we have direct evidence of the clearest sort that the higher insects do actually perceive the difference between various colors. Nay, more, their perception in this respect appears to be closely analogous to our own; for while the bees had no difficulty in discriminating between red, orange, or yellow, and green, they did not seem to perceive so marked a distinction between green and blue. Now, this fact is very like that which we perceive to hold good with the human eye, for all of us are much more likely to confuse green and blue than any two other hues.

If, then, bees and wasps, as Sir John Lubbock has shown, and butterflies, as we may infer from other observations, do possess this developed color-sense, we may ask, how did they obtain it? In all probability it grew up side by side with the growth of bright-hued flowers. Just as those blossoms which exhibited the greatest tendency to display a brilliant whorl of tinted leaves, in the neighborhood of their stamens and pistils, would best succeed in attracting insects, so, in return, those insects whose eyes were most adapted for distinguishing the pink and yellow blossoms from the green foliage would best succeed in procuring food, and would thus live down their less gifted competitors.

It may reasonably be asked. How could an animal without a color-sense develop such a faculty by the aid of natural selection alone? At first sight the question seems indeed a difficult one; but it is