Fire ants mate in nuptial flights hundreds or thousands of feet in the air. They use environmental cues to both synchronize mating flights with other colonies and ensure that conditions are good for founding new colonies. This means that the afternoon following a rain (particularly if it’s been dry for a while) hundreds and thousands of newly mated queens can be found wandering the ground in search of a good nest site. (The dying males are also in abundance.) The foundresses may start colonies alone, in groups, or even join existing colonies. In the meantime these ants explore every available nook and crevice which may provide both refuge and a good start on a nest tunnel.
The alates are easiest to find in areas where they have trouble going to ground. For instance, on a hard gravel pathway or a paved road you may turn a leaf or a stone and find a dozen queens wedged underneath. In some cases, like the picture at the beginning of this post, I have even found piles of fire ant alates apparently attempting to hide under each other (or at least conserve moisture). When not hiding, the wandering alates are easy to spot due to their large, shiny abdomens and awkward, trundling walk.
The sudden surge in these slow, mostly defenseless sexuals (the queen’s stinger/ovipositor is modified for egg-laying) makes a tasty meal for many predators. Don’t think a queen is completely helpless however. I’ve personally observed a foundress with an egg clutch tear a dozen invading fire ant workers limb from limb with her mandibles alone.