There’s a trick at the top of evolutionary biologist James Mallet’s Web page, where five pairs of tropical Heliconius butterflies pose in a double row.
Each pair flashes a distinctive pattern of colored bands across dark wings. Read the caption closely. Partners in the pairs may look alike, but they don’t belong to the same species. Instead, the five butterflies with blatantly mismatched colors in the top row do belong to the same species. The bottom five, equally mismatched ones belong to a single other species.
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