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> Pls post photos of the beetle with a polarizer!
Sorry that took a while. Here's a ded specimen of the common green rose chafer Cetonia aurata in sunlight and through a right circular polarizer filter. The iridescent green reflected from the beetle's carapace is a structural color and entirely left-polarized light due to the molecular structure of its chitin cuticula. Those beetles are the only objects in nature known to do this. Why - we just don't know. Most of those beetle species don't seem to react to polarized light. Only some South American beetles maybe do. 
https://pubmed.ncbi.nlm.nih.gov/16564066/
https://pubmed.ncbi.nlm.nih.gov/22155007/
https://pubmed.ncbi.nlm.nih.gov/20302426/