Arthropod Struct Dev. 2026 Aug 4;94:101558. doi: 10.1016/j.asd.2026.101558. Online ahead of print.
ABSTRACT
Sexually dimorphic coloration is common in Lepidoptera. In addition to differences in pigmentation, Lepidopterans also exhibit sexually dimorphic structural coloration. Lycaenidae are unique among Lepidoptera due to the presence of a multilayer pepper-pot photonic structure located within the body of their cover scales. While sexually dimorphic pepper-pot structures in Lycaenidae have previously been observed between male blue scales and female melanic scales, the nature of sexually dimorphic photonic structures within non-pigmented scales has yet to be examined in detail. In this study, we examined the morphology and reflective capabilities of cover scales from the sexually dimorphic postdiscal forewing region of summer form Celastrina neglecta (W. H. Edwards, 1862) (Lycaenidae: Polyommatinae) specimens to determine the basis of sexually dimorphic structural coloration in the species. Wing region and single-scale reflectance were compared based on spectrometry. Scale morphology was compared based on scanning electron, transmission electron, and light microscopy. Wing region analyses revealed that males and females possess statistically different wing region reflectance. Males exhibit high reflectance of violet (400-450 nm) and low reflectance in the 451-750 nm range, while females exhibit lower reflectance of violet and higher reflectance in the 451-750 nm range. Single-scale analyses revealed both blue and clear cover scales in the region of interest. While male and female scales exhibit similar reflective properties, females possess more clear scales in the dimorphic region than males. Morphological analyses indicate that the ridges and cross-ribbing of clear scales are more densely packed than their blue counterparts. Additionally, blue scales exhibit a fully developed pepper-pot photonic structure within the scale lumen, while clear scales possess irregular photonic structures that are frequently absent from the scale lumen.
PMID:42551101 | DOI:10.1016/j.asd.2026.101558
