Stable structural color patterns displayed on transparent insect wings

Abstract

Color patterns play central roles in the behavior of insects, and are important traits for taxonomic studies. Here we report striking and stable structural color patterns-wing interference patterns (WIPs) -in the transparent wings of small Hymenoptera and Diptera, patterns that have been largely overlooked by biologists. These extremely thin wings reflect vivid color patterns caused by thin film interference. The visibility of these patterns is affected by the way the insects display their wings against various backgrounds with different light properties. The specific color sequence displayed lacks pure red and matches the color vision of most insects, strongly suggesting that the biological significance of WIPs lies in visual signaling. Taxon-specific color patterns are formed by uneven membrane thickness, pigmentation, venation, and hair placement. The optically refracted pattern is also stabilized by microstructures of the wing such as membrane corrugations and spherical cell structures that reinforce the pattern and make it essentially noniridescent over a large range of light incidences. WIPs can be applied to map the micromorphology of wings through direct observation and are useful in several fields of biology. We demonstrate their usefulness as identification patterns to solve cases of cryptic species complexes in tiny parasitic wasps, and indicate their potentials for research on the genetic control of wing development through direct links between the transregulatory wing landscape and interference patterns we observe in Drosophila model species. Some species display sexually dimorphic WIPs, suggesting sexual selection as one of the driving forces for their evolution.

The role of random nanostructures for the omnidirectional anti-reflection properties of the glasswing butterfly

“…The total reflection is remarkably low in the visible regime. In comparison with the bare glass, which is known to reflect about 8% of light under normal incidence (two surfaces 13 ), the glasswing reflection of 2% (two surfaces) in the visible regime is about four times lower while their refractive indices are quite close [14][15][16] . The low reflection is also observed for wavelengths in the ultraviolet to near infrared (NIR) regime.…”

“…For an easy comparison of different models and shapes, we use normalized scaling z à ¼ z h in the following. We assume a typical refractive index of chitin and air without absorption as n chitin ¼ 1.57 [14][15][16] and n air ¼ 1, respectively. The dash-dotted line in Fig.…”

Can the narrow red bands of dragonflies be used to perceive wing interference patterns?

“…The spatial distribution of membrane thickness can be observed by human color vision in dark field microscopy on insect species with thinner wings. These patterns are referred to as wing interference patterns (WIPs; Shevtsova et al., 2011). We find that wing membrane thicknesses presented vary from 1.5 to 6 μm.…”

“…Hereafter, we do not expect any major changes to the WIPs. In one study, WIPs were shown to be preserved over 100 years (Shevtsova, Hansson, Janzen, & Kjaerandsen, 2011). The cameras were mounted on a linear translation stage and were scanning along the insect boards with the optical axes perpendicular to the boards.…”

SUPER RESOLUTION LASER RADAR WITH BLINKING ATMOSPHERIC PARTICLES ---- APPLICATION TO INTERACTING FLYING INSECTS (Invited Paper)

“…Equivalently, remote nanoscopy may be conducted of insect wing membranes using multi-band lidars, which, so far, have been developed for conventional aerosol particle characterization [17,18]. The membrane thickness is known to be species specific [19]. As an example of useful data retrievable by optical means we present push-broom hyper-spectral images (VNIR and SWIR Hyspex camera, Norsk Elektro Optikk) of a wasp with selected examples of coherent and incoherent scatter spectra from both body and wings (See Fig.…”