Be happy you learned this little ditty before a foray into the Southern woodland regions of North America. This saying originated in North America as a way to distinguish the venomous coral snake–recognizable by its red, yellow, and black banded skin–from nonvemonous look-a-likes. There are only two species of coral snake found in North America, the eastern coral snake, or harlequin snake (Micrurus Fulvius) and the Arizona coral snake (Micruroides euryxanthus). “Red on yellow” refers to the red and yellow striped bands that run down the the snake’s body. Variations of the phrase include, “Red on Yellow Kills a Fellow, Red on Black, Venom Lack,” and “Red on yellow kills a fellow; red on black, pat it on the back.” Unfortunately the saying’s usefulness wanes outside of North America, where in regions like India, the coral snakes have different color and band patterns on their skin. The image above is of the charlatan coral snake, the scarlet king snake (Lampropeltis Triangulum Elapsoides).
Image by Flickr Member: Pierson Hill