Flight Takeoff Performance from the Water Surface in Riparian Beetles

Riparian terrestrial insects face floods or accidental water exposure; however, their ability to fly off the water surface is unclear. Interspecific variation in takeoff latency and probability was evaluated in 25 beetle species. Non-riparian species did not initiate flight from the surfaces of experimental lentic water, whereas 19 riparian species did. Takeoff latency varied greatly, with a remarkable influence of shoreline distribution and body size. High-speed videography demonstrated that, upon landing, Tachyura laetifica (Carabidae) clearly adhered to the water surface and progressively detached from the interface by pulling its body upward. In contrast, upon landing, Thinodromus eminens (Staphylinidae) quickly stood in position and took off almost immediately. Under reduced surface tension, takeoff performance declined, indicating the importance of a stable standing position for takeoff. In the laboratory, both species demonstrated takeoff under a low-velocity flow. The results suggest that in riparian beetles, takeoff from the water surface is a common behavioral response, which may help them fly off rapidly to avoid water-level fluctuations or predation risk.