Spinybacked Orbweaver

It's kind of like how older folks here in Oklahoma call an alligator snapping turtle a "loggerhead." To reptile people (and most others), a loggerhead is a sea turtle. :-)

ya lots of people living in florida call them crab spiders, i do

Common names are transient, regional, and ambiguous, though I can see some people calling this a "crab spider". What really matters is the scientific name.

I agree with ForestDragon. this is without a doubt the Spiny-backed Orbweaver Spider.