Eunjin Yang1, Jae Hak Son2, Sang-im Lee3, Piotr G. Jablonski2,4,* & Ho-Young Kim1,5,*
1Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 08826, Korea. 2 Laboratory of Behavioral Ecology and Evolution, School of Biological Sciences, Seoul National University, Seoul 08826, Korea. 3Daegu-Gyeongbuk Institute of Science and Technology School of Undergraduate Studies, Daegu 42988, Korea. 4 Museum and Institute of Zoology, Polish Academy of Sciences, Wilcza 64, Warszawa 00-679, Poland. 5 Big Data Institute, Seoul National University, Seoul 08826, Korea.
*Correspondence and requests for materials should be addressed to P.G.J. or to H.-Y.K.
Abstract
Water striders are water-walking insects that can jump upwards from the water surface. Quick jumps allow striders to avoid sudden dangers such as predators’ attacks, and therefore their jumping is expected to be shaped by natural selection for optimal performance. Related species with different morphological constraints could require different jumping mechanics to successfully avoid predation. Here we show that jumping striders tune their leg rotation speed to reach the maximum jumping speed that water surface allows. We find that the leg stroke speeds of water strider species with different leg morphologies correspond to mathematically calculated morphology-specific optima that maximize vertical takeoff velocity by fully exploiting the capillary force of water. These results improve the understanding of correlated evolution between morphology and leg movements in small jumping insects, and provide a theoretical basis to develop biomimetic technology in semi-aquatic environments.