Are you serious? No offense, but I think snake-insertion has got BAD IDEA written all over it.

Things you should know:
1. Snakes have mites. Even the healthiest snakes can occasionally pick up these little black buggers that will come off and walk around on your skin if you're just *holding* the snake...I can't imagine it could be healthy to have them detach and stroll around inside your body.
2. Snakes bite. According to the Crocodile Hunter, if you hold them firmly behind the head it's pretty safe, but I don't consider that a nice thing to do to a pet. And I doubt it's possible if you've got the other end stuffed up into your pussy.
3. Snakes thrash. What type of snake are we talking here? A skinny one (ie kingsnake), or a really fat one (ie boa or python or something)? Because I can tell you from experience, if you handle a python of that size in a way it doesn't like, even if it doesn't bite, it will thrash around like nobody's business, and I can't imagine that will be a comfortable thing for you.
4. Snakes have scales. The scales only point one way. If you rub a snake towards its head (the direction you'd be trying to insert it), it gets pissed off, the scales scratch you, and depending on the health of your snake, the scales might even flake off a bit. Then you've got snake scales embedded in your pussy walls. Mmm, sanitary stuff.
5. It's mean. In general snakes like warm places, but believe me, a pussy doesn't count here. I had a pet snake once. (*Sniff* Beavis, you are sorely missed!) Please, don't do it!!!