page_title: Chrysiridia rhipheus
section_title: Wing microstructure
hierarchical_section_title: Chrysiridia rhipheus / Description / Wing microstructure
caption_attribution_description: Deutsch&#x3a;&#32; Chrysiridia rhipheus - Zwei Ansichten des gleichen ExemplarsEnglish&#x3a;&#32; Madagascan sunset moth - Two views of same specimenFrançais&#x202f;&#x3a;&#32; Chrysiridia rhipheus - Deux vues du même spécimen
context_page_description: Chrysiridia rhipheus, the Madagascan sunset moth, is a species of day-flying moth of the family Uraniidae. It is considered one of the most impressive and appealing-looking lepidopterans. Famous worldwide, it is featured in most coffee table books on Lepidoptera and is much sought after by collectors, though many older sources misspell the species name as "ripheus". It is very colourful, though the iridescent parts of the wings do not have pigment; rather the colours originate from optical interference. Adults have a wingspan of 7–9 cm.
  Dru Drury, who described the moth in 1773, placed it in the genus Papilio, considering it a butterfly. Jacob Hübner placed it in the moth genus Chrysiridia in 1823. Later redescriptions led to junior synonyms such as Chrysiridia madagascariensis.
  At first the moth was thought to be from China or Bengal, but was later found to be endemic to Madagascar. It is found throughout the year in most parts of the island, with peak populations between March and August, and smallest numbers between October and December. Females lay about 80 eggs under the leaves of Omphalea spp.
context_section_description: Unlike in many other moths, the colour of C. rhipheus's wings does not come from pigments. The colour originates from coherent scattering and interference of light by the microstructure of the ribbon-like scales covering the moth's wings. These structural characteristics make this species and its Neotropical relative Urania common subjects of research in optical science.
  The colours on the Madagascan sunset moth's wings are produced by the conjunction of two optical phenomena:
  An air-cuticle multilayer in the scales creates optical interference. Each scale contains cuticle layers with randomly located blocks of cuticle that hold them in place and maintain an air gap between them. The layers and air gaps are narrower than the wavelength of visible light. The structure varies from one layer at the proximal end of each scale, to about six layers at the distal end. This multilayer structure strongly reflects certain wavelengths of light, which are determined by the thicknesses of the layers and the angle at which the light hits the scale.
  The scales are highly curved, which creates inter-scale reflection. This mechanism is unusual among Lepidoptera. The proximal part of each scale is almost flat; the scale then gradually curves up and then steeply bends down at the distal end, covering the proximal part of the next row of scales. Because of this shape, adjacent rows of scales have valley-like grooves between them. This allows light to strike one scale, reflect at a roughly 90° angle, strike the next scale, and be reflected away from the wing. Because the angle of each reflection is far from normal incidence, the interference effect favours reflection of different colours of light than are seen when light strikes near the top of the curved part of the scale.
  The colour seen in each part of the wing is the combination of the colours reflected by these two effects.
  Because the cuticle layers are arranged in rows, with a cylindrical curve, the amount of the second type of reflection is dependent on the polarization of the incoming light. This makes the moth's overall colour polarization-dependent. Many insects can detect polarization of light, so it has been proposed that this feature may be used as a visual signal between moths. This has not yet been studied, however.
caption: Both sides of Chrysiridia rhipheus
exif: {"Image ImageDescription": "Chrysiridia rhipheus MHNT", "Image Orientation": "Horizontal (normal)", "Image XResolution": "240", "Image YResolution": "240", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS6 (Windows)", "Image DateTime": "2013:02:02 18:09:26", "Image ExifOffset": "2298", "Image XPTitle": "[67, 0, 104, 0, 114, 0, 121, 0, 115, 0, 105, 0, 114, 0, 105, 0, 100, 0, 105, 0, ... ]", "Image XPKeywords": "[67, 0, 104, 0, 114, 0, 121, 0, 115, 0, 105, 0, 114, 0, 105, 0, 100, 0, 105, 0, ... ]", "Image Padding": "[]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "4640", "Thumbnail JPEGInterchangeFormatLength": "4476", "EXIF ColorSpace": "Uncalibrated", "EXIF ExifImageWidth": "10176", "EXIF ExifImageLength": "4912", "EXIF Padding": "[]"}