Interfacial locomotion of water walking insects with alternating tripod gait

Microvelia and Mesovelia are some of the insects which locomote on both water and land. Unlike the rowing gait of Gerridae, these water walkers employ an alternating tripod gait during their locomotion. In both organisms, middle legs and hind legs shed a pair of vortices during their power strokes. In the case of microvelia, hind legs re-energize the vortices shed from the middle legs. However, such vortex recapture phenomenon is absent in water locomotion of Mesovelia. Here, we unveil the role of vortex interactions in water walking insects. To visualize and quantify these vortices, we used the particle imaging velocimetry (PIV) technique. Moreover, we also built a physical model to study the role of various parameters related to the locomotion of Microvelia, such as stroke frequency and stroke duration on the vortex interactions. Furthermore, this work might guide the designs of efficient microscale water walking robots.