David Attenborough is in North America with two large glass jars in front of him, each containing a snake with red, black and yellow stripes. But one is a harmless king snake while the other is highly venomous coral snake. Luckily, the locals have a saying to tell which is which: "Red and black, venom lack. Red and yellow, can kill a fellow." In one snake the red stripes are next to the black ones, in the other the red stripes are next to the yellow ones. David takes the snake with the red and black combination out of the jar. It is the king snake and therefore harmless.