Revisiting absent trails: Spatial memory of trail pheromones in termites.

Termites are social insects that coordinate cooperative behavior through pheromones. Trail pheromones play a central role in foraging and recruitment. Traditionally, termite navigation has often been modeled as a reflexive response to the current gradient of pheromone concentration, implying a stimulus-driven, taxon-type mechanism without necessarily requiring internal spatial representation. However, it remains unclear whether termites can form and utilize spatial information about the location of chemical cues. In this study, we investigated whether previous contact with a trail pheromone can bias termite movement after the pheromone-marked substrate has been removed. In the primary immediate test, entries into the exact target-side circle were not significantly higher in the pheromone condition, indicating that the effect was not a strong immediate return to a precise point. However, across the extended test phase, pheromone-exposed termites showed more entries and inward excursions toward the area where artificial trail pheromone had previously been presented, especially when broader target zones were considered. Together, these results suggest that termites can retain or use coarse spatial information about a previously encountered trail-pheromone cue, resulting in broad spatial bias rather than accurate point revisitation. Our findings extend the traditional view of trail pheromones as purely immediate stimuli by suggesting that pheromone experience can influence later movement after cue removal. This provides a cautious basis for considering how chemical cues may contribute to locale-like navigation in termites.