CENTRAL FLORIDA CRITTER OF THE DAY: Redheaded Pine Sawfly larvae (Neodiprion lecontei)
As the common name indicates, these are a pest of pine trees. On a different note, they are not Diptera, but a member of Hymenoptera which includes bees, ants and wasps.
For some reason, these guys were lost and three were discovered on my Red Cedar that had unceremoniously died in late August from reasons unknown. Perhaps they are looking for a place to spin a cocoon. although they generally make cocoons in the soil. The fact sheet notes that if flooding presents a problem they may also use needles, limbs and trunk of the tree. My yard is known for occasional flooding.