Hummingbird hawkmoths may have their own version of being left-handed or right-handed, using one preferred eye and one side of their long proboscis together to search flowers for nectar. This discovery, made by a team of biologists at the University of Konstanz, reveals how creatures with small brains save mental energy when making precise physical movements. In a study titled Conservation of a lateralized visuomotor axis in hawkmoth proboscis probing, published in the Proceedings of the National Academy of Sciences (PNAS), researchers Lochlan Walsh and Anna Stöckl tracked how these day-active insects check food sources while hovering in mid-air.
The study found that individual moths consistently swing their proboscis towards either the left or right side of their body while searching for nectar. This side preference varies between insects, mirroring the differences seen in human handedness. Importantly, this preference emerges immediately during the moths' first attempts, suggesting it's an innate trait. By creating computer models of the insects' vision, the researchers discovered that each moth aligns its favored proboscis side with a dominant eye, ensuring a direct view of the flower's touched area.
This internal alignment is a processing shortcut, saving valuable mental energy. When part of a moth's main eye is covered, it adjusts its body position to maintain the original eye-proboscis strategy, rather than moving its limbs. This approach is unique to hawkmoths and demonstrates how physical adaptations can solve complex movement tasks without needing a large brain. By pairing a main eye with a preferred feeding side, the insect creates a fixed visual-motor system that simplifies flight and feeding adjustments.
The study highlights the efficiency of lateralization in simplifying difficult tasks, whether reaching for a coffee cup or using the proboscis to search for nectar. Hummingbird hawkmoths also rely on live visual feedback to direct their proboscis, using constant sight to track and fine-tune their movements. When their eyes are covered, they can still touch the flower but lose the ability to recognize clear shape patterns on petals, slowing their nectar search.
The Macroglossum stellatarum species faces a unique challenge due to its long proboscis, which can only move forwards and backwards by about 1.5 centimeters. To line up its proboscis with a target, the moth makes main position changes by steering its whole body in mid-air, using tiny proboscis movements to probe the flower's surface. This combination of whole-body flight adjustments, precise proboscis control, and side-specific eye targeting allows the insect to feed efficiently while hovering.
In conclusion, the study reveals how hummingbird hawkmoths use lateralization to simplify complex tasks, demonstrating the efficiency of nature's design in saving mental energy and enhancing precision in physical movements.
