Page:The Zoologist, 4th series, vol 5 (1901).djvu/356

328 insects? From experiments made with Ants, Lord Avebury considers as proved that these insects perceive the ultra-violet rays. As he remarks:—"As every ray of homogeneous light which we can perceive at all appears to us as a distinct colour, it becomes probable that these ultra-violet rays must make themselves apparent to the Ants as a distinct and separate colour (of which we can form no idea), but as unlike the rest as red is from yellow, or green from violet. The question also arises whether white light to these insects would differ from our white light in containing this additional colour. At any rate, as few of the colours in nature are pure, but almost all arise from the combination of rays of different wave-lengths, and as in such cases the visible resultant would be composed not only of the rays which we see, but of these and the ultra-violet, it would appear that the colours of objects and the general aspect of nature must present to them a very different appearance from what it does to us." The late Prof. Riley was of the same opinion:—"So far as experiments have gone, they show that insects have a keen colour sense, though here again their sensations of colour are different from those produced upon us." It is said that certain night-flying insects invariably visit white flowers, as we reasonably believe, because of the easy detection of that colour in an obscure light, and we may accept the night preference to such flowers as an undoubted fact. But we cannot say that the hue which we describe as white is the same as that apprehended by the insects. Distinct it must undoubtedly be to secure the permanent selection of their visits, but we can say no more. Because an insect