What is this ant doing out and about this time of year? It is December, after all.
There hasn't been rain for weeks.
My son found her walking on the driveway.
She's definitely a Solenopsis because the antennal club is two segments, not three. It seems rather odd, but other species of fire ants are thought to have nuptial flights throughout the year, not just the typical ones that occur on warm, humid days in the spring or summer.
Looking back, I see that I found a single queen that was probably the same species under a rock in November of 2009 (see, blog posts are useful sometimes).
They both look like Solenopsis amblychila based on Trager's (1991) description: the queen has no clypeal teeth and the shape of the head is cordate when viewed face on.
As to what she is doing, my best guess that a mated queen would be trying to enter an established nest this time of year. What do you think?
Trager, J. C. 1991. A revision of the fire ants, Solenopsis geminata group (Hymenoptera: Formicidae: Myrmicinae). Journal of the New York Entomological Society, 99:141-198. (.pdf available here)