Fine Structure of Wing Scales in <I>Chrysozephyrus Ataxus</I> Butterflies

Abstract

We performed scanning electron microscopy observations of the scales on the dorsal surfaces of wings of male and female Chrysozephyrus ataxus butterflies. The male butterfly has curly scales on the blue or green wings. It was deduced that the interference of the selective incident rays with the wavelength in $560 nm ! ! $420 nm and $340 nm ! ! $250 nm occurs incoherently by layers $270 nm thick piled in the flat grooves which are enclosed by the ridges and ribs on the curled scale. The metallically glittering green-violet hues of the male wings is thereby attributed to the reflection of the human visible rays in $560 nm (green) ! ! $420 nm (violet). The vivid violet marks in the female's forewings were also explained as the result of reflection of the incident rays in $400 nm ! ! $300 nm from the layers $190 nm thick in the flat grooves on the dorsal scale. Although the monolayered cuticle structure was observed on the ridges of these scales, its contribution to the wing colouration must be less because of a small width of the ridges as compared with the flat grooves. The scales in the dark brown areas of the female wings are different in structure from these scales; they have not any layers but windows enclosed by the ridges and ribs. Most of the light through the windows is absorbed in the lower laminae containing the eumelanin. These results were deduced using data of a previous optical measurement by Imafuku et al. (Zool. Sci. 19 (2002) 175) and elucidated consistently their conclusion.

Photonic Crystal Structure and Coloration of Wing Scales of Butterflies Exhibiting Selective Wavelength Iridescence

“…( a ) Transmission image; ( b ) Reflection image; ( c ) Enlarged image of a scale in (b) (adapted from [14]).…”

“…( a ) Law-magnified image of curled scales; ( b ) A curled scale; ( c ) Ridges and cross ribs in the scale; ( d ) Enlarged image of the ridges and ribs; ( e ) Cross-section of a groove enclosed by the ridges and ribs, revealing seven piled layers; ( f ) Schematic of the fine structure of the scale (adapted from [14]).…”

“…( a ) Law-magnified image; ( b ) Ridges and cross ribs in a violet scale (left) and a dark brown scale (right); ( c ) Enlarged image of the ridges and ribs in the violet scale; ( d ) Cross-section of a groove plate enclosed by the ridges and ribs, revealing triple piled layers (adapted from [14]).…”

“…We would like to acknowledge the great contributions of our collaborators, particularly, the coauthors of the papers cited in references [11,12,13,14], to the present investigations. The study was supported partially by European Commission and Ministry of Education, Youth, and Sports of the Czech Republic (project No.…”

“…The iridescence is caused by the interference of incident light reflected with a kind of blazed diffraction grating of the scales that has a high efficiency in a shorter wavelength range of 200~450 nm. We have investigated the coloration in different areas in the wings of a male Euploea mulciber ( E. mulciber ) butterfly [11], and male and female Chrysozephyrus ataxus ( C. ataxus ) butterflies [14]. They are famous for vivid violet-green iridescent wings, similar to A. meliboeus and S. charonda .…”