The scarlet kingsnake's red, yellow, and black markings closely resemble those of the highly venomous coral snake. This mimicry can fool predators, but humans can keep the two species straight with the rhyme: "Red on yellow, kill a fellow. Red on black, friend of Jack."
Kingsnakes get their name because they eat (among other things) rattlesnakes. A king snake is very resistant to rattlesnake venom, so it can sniff out a rattlesnake and then kill it by wrapping around the rattlesnake and squeezing it.