Even if you get bitten by the fire ants you should catching them when you try. Nothing else looks like the fire ants so there can be no question of what they are. They only spawn in the rental areas not in the areas surrounding the National Park or in the hidden area. I don't ever use repellent there .. usually my sims don't stay that uncomfortable or I have them take a bath/sleep it off or get other moodlets to top it. I don't always have it off but I usually turn rain/thunderstorms off in options before they go on vacation there.