In Willa Cather’s most important novel, My Ántonia, the killing of a rattlesnake marks the coming of age of the young man Jimmy. Before this incident, he had been regarded as a mere boy by Ántonia, but afterwards, she perceived him with respect as a young man. In the snake-killing scene, the poison was described as “a thread of green liquid,” although in actuality, rattlesnake venom is whitish yellow, not green. The idea that snake venom is green is well rooted in American folk stories about snakes. This article discusses snake loreinvolving the green motif, and the symbolic use of green in folklore and literature. Cather’s use of green venom in the young man’s initiation rite is particularly appropriate not only because it fits into the folklore vernacular of the people butalso because as a symbol it carries multiple conflicting yet unified meanings.