Note on the iridescent colours of birds and insects

Abstract Considerable interest attaches to the origin of certain forms of brilliant colouring which are of frequent occurrence in the animal world, though hardly represented among plants. The colours in question are those which are not due to ordinary pigment, and which change with the angle of incidence of the light. The most brilliant examples are to be found amongst birds and insects. Fishes, and a few reptiles, exhibit colours of the.same kind, but not so conspicuously. During the last 10 or 12 years I have examined some hundreds of cases of this sort of colour production, and quite recently Michelson has published investigations on the same subject, and refers to a somewhat similar paper by Walter, “Oberflächen and Schillerfarben,” dated 1895, of the existence of which I was not before aware.