Royal Walnut Moth
This vicious-looking (but rather harmless) caterpillar can often reach lengths of 6 inches. The large spines and black and orange horns are meant the scare away potential predators such as birds.
Hickory-Horned Devil/Royal Walnut Moth Citheronia regalis (Fabricius) (Family: Saturniidae)
Habitat: Hardwood forests
Florida range: Northern Florida including panhandle
Larval host plants: walnut (Juglans species) and hickory (Carya species) trees
Flight: June-September
Occurrence: Common
Link for more information: http://creatures.ifas.ufl.edu/bfly/regal_moth_photo2.htm