That herons have a peculiar possible light-producing apparatus is well known. These are called powder-down patches, and can be found by turning up the long feathers on the heron's breast, where will be found a patch of yellow, greasy material that sometimes drops off or fills the feathers in the form of a yellow powder. This powder is produced by the evident decomposition of the small feathers, producing just such a substance as one might expect would become phosphorescent, as there is little doubt that it does.
The cranes and herons are not the only birds having these oily lamps, if so we may term them. A Madagascar bird, called kirumbo, has a large patch on each side of the rump. The bitterns have two pairs of patches; the true herons three, while the curious boat-bills have eight, which, if at times all luminous, would give the bird a most conspicuous, not to say spectral appearance at night.
Some years ago a party of explorers entered a large cave on the island of Trinidad that had hitherto been considered inaccessible. To their astonishment they found it filled with birds which darted about in the dark in such numbers that they struck the explorers and rendered their passage not only disagreeable, but dangerous. The birds proved to be night hawks, known as oil birds, and in great demand for the oil they contain, and it is barely possible that these birds are also light-givers. The powder-down patches of the oil bird are upon each side of the rump.
As to the use of such lights to a bird there has been much conjecture; but it is thought that it may be a lure to attract fishes. It is well known that fishes and various marine animals are attracted by light, and a heron standing motionless in the water, the light from its breast, if equal to two candles, would be plainly seen for a considerable distance by various kinds of fishes, which would undoubtedly approach within reach of the eagle eye and sharp bill of the heron and so fall victims to their curiosity. If this is a true solving of the mystery it is one of the most remarkable provisions of nature.
There is hardly a group of animals that does not include some light-givers of great beauty; but it is not generally known that some of the higher animals also produce light at times. Renninger, the naturalist, whose studies and observations of Paraguay are well known, tells a most remarkable story of his experience with the monkey known as Nyctipithithecus trivigatus. He was in complete darkness when he observed the phenomenon, which was a phosphorescent light gleaming from the eyes of the animal; not the light which appears in the eye of the cat, but shafts of phosphorescent light which were not only distinctly visible, but illumined objects a distance of six inches from the animal's eyes.
The subject is an interesting one and research among the various phenomena disclosed by naturalists may discover many other animals capable of strange illuminations.
THE PINK HOUSE IN THE APPLE TREE.
NELLY HART WOODWORTH.
