Reverse color sequence in the diffraction of white light by the wing of the male butterfly Pierella luna

The butterfly Pierella luna (Nymphalidae) shows an intriguing rainbow iridescence effect: the forewings of the male, when illuminated along the axis from the body to the wing tip, decompose a white light beam as a diffraction grating would do. Violet light, however, emerges along a grazing angle, near the wing surface, while the other colors, from blue to red, exit respectively at angles progressively closer to the direction perpendicular to the wing plane. This sequence is the reverse of the usual decomposition of light by a grating with a periodicity parallel to the wing surface. It is shown that this effect is produced by a macroscopic deformation of the entire scale, which curls in such a way that it forms a "vertical" grating, perpendicular to the wing surface, and functions in transmission instead of reflection

Butterfly wing colours: scale beads make white pierid wings brighter

The wing-scale morphologies of the pierid butterflies Pieris rapae (small white) and Delias nigrina (common jezabel), and the heliconine Heliconius melpomene are compared and related to the wing-reflectance spectra. Light scattering at the wing scales determines the wing reflectance, but when the scales contain an absorbing pigment, reflectance is suppressed in the absorption wavelength range of the pigment. The reflectance of the white wing areas of P. rapae, where the scales are studded with beads, is considerably higher than that of the white wing areas of H. melpomene, which has scales lacking beads. The beads presumably cause the distinct matt-white colour of the wings of pierids and function to increase the reflectance amplitude. This will improve the visual discrimination between conspecific males and females

Ultraviolet Coloration in Tiger Swallowtail Butterflies ( Papilio glaucus

Tiger swallowtail butterflies in the genus Papilio have an ability to visually distinguish between a large array of colors including those in the ultraviolet spectrum (UV). However, very little is known about UV reflectance patterns in these butterflies. Using a combination of UV photography and spectral analysis, we here show that several areas on the wings of tiger swallowtails reflect UV light including areas of blue scaling and the anterobasal region of the hind wings. We also discuss how a low level of UV reflectance from the wing membrane itself may be combined with UV photography to quantify wing wear. This technique could be used to objectively place wild-caught individuals into wear classes, approximating their age. Finally, we examine male mating preferences for pristine or artificially aged females and present preliminary results that suggest a strong preference for those that are pristine