Skydiving acrobatics and controllable leaping redefines springtails

Springtails (Arthopoda: Collembola) have been erroneously portraited as impulsive jumpers with poor locomotion control and maneuvering abilities. Paradoxically, for these Collembolans that live on the surface of water, these locomotion skills are crucial for survival by evading a host of aquatic, semiaquatic and terrestrial predators. In this talk, we will describe our discovery of how semi-aquatic springtails (Isotomurus retardatus) execute controlled leaping and landing from the surface of water by changing their body posture and exploiting the tightly-coupled physics of two anatomical structures – their tail-like appendage (furcula) and a hydrophilic tube-like structure (collophore). For take-off, we discover that springtails control their trajectory angle, speed, and rotation rate by modulating the propulsive force generated by the furcula through the collophore interfacial adhesion. Through biological experiments and mathematical modeling, we demonstrate that simple body angle enables this directed control. In mid-air, the body posture change, from a linear to a U-shape, which influences aerodynamic forces and thus self-righting. We confirm self-righting using vertical wind tunnel experiments and 3d-printed physical models. And finally, for landing, we reveal how the collophore provides stability for perfectly landing on their feet (>85% of the time). Together, our work sees springtails in a new light as actively-controlled and directional jumpers as well as perfect landers, reinforcing why collembolans are one of the most diverse and abundant animal taxon on the planet. Our results can be applied to improving controlled jumping and landing in small robots.