Fear is an emotion, and we can’t know about whether animals (or depending on where you fall on the qualia debate, other humans) feel that emotion. We can measure their behavior, though, and there are a great many studies on animal fear and avoidance behaviors, including ants.

Ants don’t have a memory in the sense that you or I think of. There is no collective memory of “avoid that place” that lives in the minds of ants or a hive because some ants had a bad time in that place, as far as we can tell. However ants deposit pheromones as they navigate the world. Other ants follow along later and maintain or update these pheromone “trails” (https://pmc.ncbi.nlm.nih.gov/articles/PMC4590477/). Ant pheromone signaling is a deep body of research but there are both positive (go this way) and negative (don’t go this way) signals.