A "bioluminescent" common cockchafer?

A common cockchafer (Melolontha melolontha), or May-bug, was filmed emitting strong light from a ring-shaped structure on its left elytron in broad daylight. These beetles are known as voracious agricultural pests but not at all for being bioluminescent. This led us to the hypothesis that a symbiont or parasite living in or under the elytron may be responsible for emitting this very strong light. Since the specimen was not preserved, we extracted intensity, frequencies and spectral information from the video to investigate this unusual phenomenon. Several options were distilled from the literature to propose what organisms might be responsible for this light phenomenon. Naturalists and the general public are really encouraged to closely inspect any chafers they encounter. If light emission is observed, please film the specimen and preserve it if possible. This will hopefully help us in the future to identify the organism(s) responsible for this remarkable light display.