Excerpts from Steve Tvedten's book "The Best Control
Fire Ant Feeding Habits
The oldest and most expendable 20% or so of the colony’s fire ant workers leave the nest to search for food. They explore 50-100 feet from the nest with an efficient looping pattern. They can gnaw on soiled clothing. Although the worker ants can chew and cut with their mandibles, they can only swallow liquids. When they encounter liquid food in the field, they swallow it and carry it back to the nest. Solid food is cut to reasonable size and carried back to the nest. They prefer protein foods, e.g., insects and meats, but will feed virtually on everything, including fruit, seeds, grease, butter, honeydew, plants, nuts, garbage, i.v. tubes, needles, body oils, etc. They love to eat tuna fish, grape jelly and Coca-Cola, so add 5% or less of boric acid or food-grade DE or borax to these baits.Keep baits out of the reach of children, pets and wildlife.
Like other ants, fire ant workers share their food with their nest mates by regurgitating it so that it can be licked or sucked up as a liquid by other ants. In this way, most ants in the nest get fed equally. This food sharing is also why slow-acting poison baits can be an effective control tactic against fire ants. You can try using 1% or less borax or boric acid with 10% sucrose in water by ant colonies for 3 - 4 months - it may take that long to get control. Try using several (filled and drilled) 35 mm film capsules per nest or sponge pieces soaked with bait.