What trick does Huck play on Jim? Why is he tricking him now when he didn’t want to before?

Huck finds a dead snake and decides that because Jim is very superstitious about those kinds of things that he will put it near him so in the morning he will see it. the plan back fires on him and the snake's mate comes back to it and then bites Jim. Huck isn't glad Jim got bit he just wanted to play a joke on him he didn't actually want Jim to get hurt. he tricks Jim because Jim is very superstitious so he thinks it would be funny.