Nature
A harmless species can borrow another's warning colors and steal its protection
Naturalist Henry Walter Bates spent 11 years in the Amazon and noticed that palatable butterfly species had evolved to look almost identical to foul-tasting, toxic ones that predators avoid. Predators that learn to avoid the toxic model also avoid its harmless mimic, without ever needing to be poisoned. Bates described the phenomenon in 1862, and it's now a textbook case of natural selection in action.