One of the two smallest species of the genus Morpho. This genus, the nobility among butterflies, contains for the most part species that have more or less brilliant blue colours on their wings. The Morpho aega is all blue, and the colour varies with the angle of the light. This is because this blue colour is produced by the refraction of incident light on the microscopic scales on the wings and is not caused by the pigment contained in the wings. Interestingly, the females of this species are yellow, quite rarely with a blue tinge.