About fire ants and floorless tarps.
I live and camp (a lot) in Texas, too.
I have used tarps a lot and hammocks more. (A hammock keeps you out of the ants and keeps you cool, too. What a deal!) Unless you are optionless in a regular campground or stuck on the only available sandbar on a river trip, there is no problem whatsoever in getting away from fire ants. They are usually pretty obvious. Nothing else has ever caused me a problem when tarp camping.
If you are stuck near fire ants, here is the easy, foolproof, entertaining, educational and generally edifying way to deal with them: Put out a sacrifice of crushed soda crackers, one cracker at each corner of your camp (15 feet away from the tarp). Next to each pile of crumbs pour one tablespoon of cooking oil or oil from a sardine can - any edible oil. The omnivorous fire ants will quickly find the crackers and they will concentrate at the sacrifice sites. Everyone will head for the banquet and stay away from you. It takes them longer to find the oil and to figure out what to do with it. So, the crackers get their attention and the oil keeps them busy. It's fun to watch. They will end up excavating every oil-covered grain of sand or forest litter, licking it off and staggering off toward the nest. Come morning each oil patch will be covered with obvious mining sites: tunnels with tailings piles at their mouths. It looks a lot like Colorado. And no ants. They are just like you after a big Italian dinner, comatose. If you stay for more than one day, renew the sacrifices in the morning and evening. This really works even on the extremely aggressive fire ants that live on riparian sand bars.