I'd probably cut the floor out and work on it from above...even though there are no snakes and spiders at my house..yep...that's the ticket.
Lee...that reminds me a of a famous story my dad used to tell about my uncle in college(God rest there souls). This was before my uncle introduced my dad to his younger sister(my mom). They lived in a house in Bloomington, Indiana they referred to as the "Shit Palace". It was there until the late 80's and the city finally tore it down. Anyway, they were living there and my uncle was upstairs with a girl and couldn't hear the music on the Hi-Fi so he went to the neighbors and borrowed a chainsaw and proceeded to cut a giant hole in the bedroom floor which happened to be the living room ceiling. This of course was during a party. Problem solved! This was the same place that had a terrible rat infestation and they were shooting the rats with BB guns and then they'd line them up on the stairway as trophies. The stories have been confirmed by many of the years.
I can tell you with absolute certainty that I wouldn't even consider crawling under a house where there was the slightest chance of encountering a snake...even a fake rubber snake or a strip of cable that appeared snake-like. A kids jump rope or an old hose...no way, no how. That's why we have all the Mexicans running around. How do you say, "crawl in right there" in Spanish?