Neophobic response of bull ants (Myrmecia midas) to odours introduced on their foraging route

Goal-oriented learning and navigation is well known in eusocial insects. The solitary foraging of nocturnal bull ants Myrmecia midas in their visually complex environment relies on path integration and landmark learning. While this species seems to be sensitive to handling and reacts to visual changes in their surroundings, not much is known about how added olfactory stimuli impact their route navigation on a vertical surface. In the current study, we added one of five different invisible odours on the trees on which foragers normally forage. We found that the bull ants showed neophobic responses to all the odours. The Tea-tree and Lavender odours showed the strongest impact on the bull ants navigation by causing detours, U-turns, and avoidance of the sensory stimuli, with the ants meandering more and scanning more frequently. The odours of Olive oil, Flax-seed oil, and Eucalyptus oil had a moderate impact on the ants navigation. These findings showed the widespread influence of non-visual chemical cues in shaping bull ant navigation and highlight the induction of neophobic responses stemming from chemical alterations on learned routes. Overall, this study contributes to the understanding of the effects of foreign odours, adding to our understanding of the complex learning processes of bull ants in their vertical navigation.