The quickest way for an ant to go from the ground to the tree trunk is by walking straight towards the tree and climbing the tree trunk. Ant will walk straight if it is guided by the pheromone trail left behind by the other ants.
The ant first decides to explore the area for food and threats before taking a decision to walk away from its current location, i.e, the ground. The ant then starts to climb the bark of the tree to reach a higher ground. It does so by leaving a pheromone trail behind. This pheromone trail helps in guiding the other ants towards a possible food source.