No such thing as a poisonous snake since poison is ingested venomous is injected as for the cat eye rule it is not a good way to tell if a snake is venomous the best way is to grab the snake turn it over and look at its poopchute for those of you unfamiliar with snakes if the scales break off into two Going to the tip of the tail its not venomous if it doesn't break off into two then it is venomous boa constrictors have cat eyesr