They are small tiny six legged insects that are red in color and their bite stings.
Wiki says : Fire ants are a variety of stinging ants with over 280 species worldwide. They have several common names including Ginger Ants and Tropical Fire Ants (English), aka-kami-ari (Japanese), and Feuerameise (German).
How stuff Works says:
Ants have tiny waists so they can wriggle their end parts freely! An ant’s waist has one or two movable parts. These parts allow the ant to twist and turn in different ways—an important feature for moving about an ant colony.
The ant's most highly developed sense is that of smell. Ants have abdominal glands that secrete a variety of pheromones, chemical substances that cause specific reactions by other individuals. Pheromones act as alarms, sex attractants, and trail markers; and they help individuals recognize each other. Ants have a well-developed sense of taste, and can distinguish sour, sweet, bitter, and salty tastes. Their sense of touch is keen. Touch, or tactile, receptors are located on the feet and on hairs on the legs. The antennae are used for smelling, tasting, and touching.
What I say:
An old friend (pass-out) dropped by in Chennai. I went over to visit him. And I ended up making his bed for him because bloody red ants stung me but apparently not him. Why me!!!
The venom of a fire ant sting causes stinging and swells into a bump. This can cause much pain and irritation at times, especially when stung repeatedly by several at once. The bump often forms into a white pustule, which is at risk of becoming infected if scratched, however if left alone usually go down within a few days. The pustules are unattractive and uncomfortable while active and, if the sting sites become infected, can turn into scars.