Page:Popular Science Monthly Volume 53.djvu/685

Rh no harm or good," an ingenuous assumption characteristic of many of the pages of that naturalist's recent book, in which the attempt to keep on both sides of the Darwinistic fence has left the author very much astraddle. Another English naturalist, Professor Poulton, has suggested that the bright under wings lead the pursuing bird to catch the insect by them, the wing membrane giving way without serious injury to the moth. But this seems to me a strained and inadequate explanation, much less satisfactory than the one afforded by the suggestion of another celebrated English entomologist, Lord Walsingham, who in a presidential address before the Entomological Society of London delivered the following passages:

"My attention was lately drawn to a passage in Herbert Spencer's Essay on the Morals of Trade. He writes: 'As when tasting different foods or wines the palate is disabled by something strongly flavored from appreciating the more delicate flavor of another thing afterward taken, so with the other organs of sense a temporary disability follows an excessive stimulation. This holds not only with the eyes in judging of colors, but also with the fingers in judging of texture.'

"Here I think we have an explanation of the principle on which protection is undoubtedly afforded to certain insects by the possession of bright coloring on such parts of their wings or bodies as can be instantly covered and concealed at will. It is an undoubted fact, and one which must have been observed by nearly all collectors of insects abroad, and perhaps also in our own country, that it is more easy to follow with the eye the rapid movements of a more conspicuous insect soberly and uniformly colored than those of an insect capable of changing in an instant the appearance it presents. The eye, having once fixed itself upon an object of a certain form and color, conveys to the mind a corresponding impression, and, if that impression is suddenly found to be unreliable, the instruction which the mind conveys to the eye becomes also unreliable, and the rapidity with which the impression and consequent instruction can be changed can not always compete successfully with the rapid transformation effected by the insect in its effort to escape."