Structural color produced by a three-dimensional photonic polycrystal in the scales of a longhorn beetle:Pseudomyagrus waterhousei(Coleoptera: Cerambicidae)

Abstract

The cuticle of the longhorn beetle Pseudomyagrus waterhousei shows a diffuse pattern of mixed blue and violet colors. These colorations arise from a dense layer of droplet-shaped scales covering the dorsal parts of the cuticle. In spite of their lack of iridescence, these colors are shown to be structural and produced by an aggregate of internally ordered photonic-crystal grains. Computer simulations confirm that the blue and violet colors are caused by face-centered-cubic crystallites which dominantly expose their (111) surface to illumination and viewing.

Photonic polycrystal in the greenish-white scales of the African longhorn beetleProsopocera lactator(Cerambycidae)

“…3). As found in other insects [13,20], the photonic structure responsible for the longhorn's coloration is located in these scales. The dimensions of the bristles found in the greenish-white regions are 20 microns in width and 95 microns in length.…”

“…The weak color selection is visible in the calculated average: the higher one, in the near infrared-arising mainly from the (100) surface-and the lower one, near 520 nm, rather intense, which provides the greenish coloration displayed by the longhorn. The broad lower UV contribution of the experimental curve is known to arise from the dispersion of the dielectric constant of the chitin [20] and its shortwavelength absorption capability, not accounted for in the simulation.…”

“…1). Some longhorns have been shown to have evolved scales with three-dimensional ordered photonic structures [20]. The longhorn specimen under study here originate from East Africa (Tanzania), but this species has presumably a much wider distribution: one specimen was observed on a light trap installed near the gate of the Nazinga Park, in the South of Burkina Faso [21] (West Africa).…”

Interplay of index contrast with periodicity in polymer photonic crystals

“…6 However, it is not clear how the strength of such resonances changes as the index contrast increases. Besides the technological applications, such systems are interesting analogues of structural color in nature (such as butterflies or beetles 7,8 ), as well as the intensity of scatter from clouds and radar imaging.…”

Bioinspired micrograting arrays mimicking the reverse color diffraction elements evolved by the butterfly Pierella luna

“…bioinspired optics | gratings | biophotonics T hree-dimensional photonic crystals (1)(2)(3)(4)(5), materials with twodimensional micro-or nanosized periodic morphologies (6)(7)(8), and one-dimensional multilayer configurations (9) have been identified as the primary cause of structural coloration in a wide variety of nonrelated biological organisms. In contrast, surfaceconfined diffraction elements for the separation of incident light into specific colors are less abundant in nature and have only been discovered in a handful of organisms (10), including a fossil polychaete (7), sea mouse Aphrodita sp.…”