Rhagovelia uses interfacial run-and-tumble locomotion to improve prey capture in flowing environments

Rhagovelia oriander is a neustonic insect native to the rivers and streams of North and South America, known for its distinctive skating movement on the water’s surface. This movement resembles the correlated random-walk pattern seen in microorganisms such as Escherichia coli . Previous studies have primarily focused on limb adaptations and biomechanics, leaving the ecological significance inadequately addressed. We combine field observations with controlled laboratory experiments using a flow mill to investigate the dynamics of R. oriander under relevant flow conditions. Our findings indicate that this insect exhibits a two-dimensional run-and-tumble motion, often incorporating lateral tumbles following straight runs (run distance: 30.7 ± 9.7 mm). We find that this behavior is resilient to changes in flow speed. In-silico simulations of predator-prey interactions demonstrated that this locomotion method significantly enhances prey capture efficiency compared to linear movement, particularly when the prey is following a rapid flow field. Our results document run-and-tumble locomotion in a millimeter-scale organism, showcasing a unique example of convergent behavior across diverse taxonomic groups and providing valuable insights into locomotion ecology while serving as a source of inspiration for bioinspired robotics and environmental exploration algorithms.