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there was a statement that Eastern Tiger Swallowtail, Papilio glaucus, was not normally observed feeding at dung, whereas the Canadian Tiger Swallowtail, Papilio canadensis, feeds frequently at dung. I've not really researched the matter, but here is a photo of Eastern Tigers feeding at the dung of the Canada Goose at a local park. Canadian Tigers do not occur in my area, I believe--low elevation in the North Carolina Piedmont.