The routes of one-eyed ants suggest a revised model of normal route following

Abstract

The prevailing account of visually controlled routes is that an ant learns views as it follows a route, while guided by other path-setting mechanisms. Once a set of route views is memorised, the insect follows the route by turning and moving forwards when the view on the retina matches a stored view. We engineered a situation in which this account cannot suffice in order to discover whether there may be additional components to the performance of routes. One-eyed wood ants were trained to navigate a short route in the laboratory, guided by a single black, vertical bar placed in the blinded visual field. Ants thus had to turn away from the route to see the bar. They often turned to look at or beyond the bar and then turned to face in the direction of the goal. Tests in which the bar was shifted to be more peripheral or more frontal than in training produced a corresponding directional change in the ants' paths, demonstrating that they were guided by the bar. Examination of the endpoints of turns towards and away from the bar indicate that ants use the bar for guidance by learning how large a turn-back is needed to face the goal. We suggest that the ants' zigzag paths are in part controlled by turns of a learnt amplitude and that these turns are an integral part of visually guided route following.

Oscillators and servomechanisms in orientation and navigation, and sometimes in cognition

“…Side-to-side movements support course control even when facing the goal direction entails facing a non-distinctive uniform white surround [58]. The experimental space did contain a distinctive black landmark to the left of the target heading, but Woodgate et al [58] painted the left eye of experimental wood ants so that they saw nothing but white when facing the target direction. Zigzagging allowed the ants to face the landmark direction frequently and then adjust their turns to travel in the target direction.…”

“…Transverse oscillations in ants-as opposed to oscillations that propel an organism straight forward such as peristalsis in fly larvae or flagellar beating in bacteria-allow frequent adjustments to head the traveller in the correct direction [8,57]. Side-to-side movements support course control even when facing the goal direction entails facing a non-distinctive uniform white surround [58]. The experimental space did contain a distinctive black landmark to the left of the target heading, but Woodgate et al [58] painted the left eye of experimental wood ants so that they saw nothing but white when facing the target direction.…”

Compensation to visual impairments and behavioral plasticity in navigating ants

“…Hence, depriving a navigating insect from one modality – or all modalities but one – does not necessarily disrupt their ability to orient. Unilateral suppression of one eye input, however, has a direct impact on the navigational performance of ants (28, 29). Monocular ants may still show evidence of recognition of learnt terrestrial cues but their navigational behavior is drastically affected, revealing an intriguing mix between flexibility and rigidity (28, 29).…”

“…Unilateral suppression of one eye input, however, has a direct impact on the navigational performance of ants (28, 29). Monocular ants may still show evidence of recognition of learnt terrestrial cues but their navigational behavior is drastically affected, revealing an intriguing mix between flexibility and rigidity (28, 29). For instance, monocular desert ants that have learnt a landmark array with one eye only are incapable of recognizing it if the eye cap has been swapped to the other eye, suggesting that there is no inter-ocular transfer of visual terrestrial cues (28).…”

Physiological properties of the visual system in the Green Weaver Ant, Oecophylla smaragdina

“…Visually guided behaviours in ants have been mostly studied in exclusively solitary foraging ants. This includes the scavenging desert ants (Cataglyphis (Wehner 2019), Melophorus (Narendra 2007) and Ocymyrmex (Müller and Wehner 2010)), predatory ants ((Myrmecia (Kamhi et al 2020;Narendra et al 2013a), Diacamma (Mukhopadhyay and Annagiri 2021), Odontomachus (Rodrigues and Oliveira 2014), Paltothyreus (Hölldobler 1980)), and non-specialist ants ((Formica (Woodgate et al 2021), Camponotus (Schultheiss et al 2015), Polyrhachis (Narendra et al 2013b)). Few studies have also investigated visual guidance in trail following ants ((Iridomyrmex (Card et al 2016), Paraponera (Harrison et al 1989), Temnothorax (Pratt et al 2001)).…”