While playing disc golf in the desert my fiancée and I were bitten by red fire ants. I was bitten three times and she was bitten twice. I can honestly say that red fire ant bites are one of the worst insect bites I have had because the itching lasts so long.
They also affect people differently. My fiancée was bitten on the thigh and it turned into a swollen, bruised, and blistered area the size of a grapefruit. The bruising did not go away for almost two weeks, and the bite was still evident almost a month later. She said it was the most painful insect bites she has ever had.
As for me, I had an itchy welt for about a week. It eventually turned into a small blister, but it was not nearly as bad as her bite.