Answer:
immediately
Explanation:
The ants move independently to search food from the nest, but at the same time they go away from the nest, they leave a way of pheromones, this is their mechanisms to return to the nest.
In average, the ants could take like 100 or 200 meters from the nest to search food, so 7 meters is a very small distance, and with the way of pheromones, they will return to their nest easily.