Let's see..
Cobra
Krait
Viper
that's three five-letter-named snakes right off the top of my head.
viper
Adder
snake
snake
viper
ophid
Screw. Snake. Stars. You have to be kidding, right?
snake
oscar
I don't think there is a snake beginning with Z... well, not a type of snake, anyway. Some pet snakes may be called "Zebedee", or what have you.
A 'snake' is a cold-blooded animal.
Nope... a young snake is called a snake.