Ultraviolet (UV) reflective and absorbent markings on wings of male Hebomoia glaucippe sulphurea butterflies are important visual markers used in mating to differentiate them from other species. The objective of our study was to determine whether these markings deteriorate in museum collections over time. We first characterized quantitatively the UV reflective and UV absorbent wing markings from fresh and naturally aged male H. glaucippe sulphurea using UV reflectance microphotography, which was calibrated with handmade reflectance standards. The results of calibrated UV reflectance photography were then compared qualitatively with the same markings using visible light photography, transmitted and reflected visible light microscopy, and scanning electron microscopy (SEM). A UV-converted Nikon D200 with a Baader Ultraviolet Venus lens filter was used to record UV reflective and UV absorbent wing markings of the specimens. The handmade reflectance standards were prepared using magnesium oxide, plaster, and carbon, photographed alongside the specimens, and used to calibrate the photographs. The easily and affordably produced handmade reflectance standards were effective in calibrating the UV reflectance digital photographs, which allowed for each pixel of the digital photographs to be used for optical densitometry measurements. Quantitative data from calibrated UV reflectance photography demonstrated little evidence of deterioration in the UV reflective markings, although there was clear deterioration in the UV absorbent markings. This quantitative data, along with the calibrated UV photographs themselves, offered complementary documentation to visible light microscopy and SEM images. Results show that both visible-spectrum and UV markings fade in naturally aging museum specimens. We conclude that by using calibrated UV reflectance photography, a relatively inexpensive technique, a baseline and eventual degradation of Lepidoptera wing markings may be quantified and may provide valuable data to clarify the mechanisms behind this degradation. With the rate of change quantified, and the mechanisms of fading understood, it is hoped that preventative measures can be taken in the future to remedy this loss of valuable data in collections.

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Author notes

Associate Editor.—Christine Johnson