Butterfly's wing has paid great attention due to its unique properties, such as attractive iridescence, super-hydrophobic
characteristics, and quick heat dissipation ability. These characteristics are closely related to its structure. The multilayer
thin-film structures that make up a butterfly's wing produce a bright iridescence from reflected daylight. In this study, we
will introduce the optical effect of viewing angle, structural characterizations and color-producing mechanism. Since the
reflectance patterns are extended in angle, we have to use a spectrophotometer equipped with an integrating sphere.
According to the result, the peak reflectrance decreasing, blue-shifts and the difference between spectra of p-polarization
and the s-polarization was enlarged when the incident angle increasing. In addition, the directional and strongly angle-dependent
reflection of the ventral wings suggests the question whether or not the wing reflections may play a role in
visual signaling by the butterflies during flight. Furthermore, we determined the shape and surface texture of the scales
by scanning electron microscope (SEM). From SEM images, the scales cover the wing membrane and appear to overlap
like roof tiles. These nanometer structures of the cover scales will decide the attractive iridescence of the wing.