Hanns Hagen Goetzke

Juvenile mantises can jump towards targets by rapidly extending their middle and hind legs. Here, we investigate how mantises can perform jumps from smooth surfaces such as those found on many plants. Stagmomantis theophila mantises possess two distinct types of attachment pads on each foot: three small proximal euplantulae (“heel pads”) with microscopic cuticular ridges and one smooth large distal pair of euplantulae (“toe pad”). Microscopy showed that the surface contact of heel pads is strongly load-dependent; at low normal forces, they make only partial surface contact due to the ridges, but at higher loads they switch to larger areas in full contact. By analysing the kinematics of 64 jumps of 23 third-instar nymphs from glass surfaces and the foot contact areas of their accelerating legs, we show that heel and toe pads fulfil distinct roles. During the acceleration phase of jumps, the contact area of the hind legs’ heel pads tripled, while that of the toe pad decreased strongly, and the toe pad sometimes detached completely before take-off. Although the middle legs also contribute to the jump, they showed a less consistent pattern; the contact areas of their heel and toe pads remained largely unchanged during acceleration. Our findings show that jumping mantises accelerate mainly by pushing with their hind legs and produce grip on smooth surfaces primarily with the heel pads on their proximal tarsus.

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Many spiders and insects can perform rapid jumps from smooth plant surfaces. Here, we investigate how jumping spiders (Pseudeuophrys lanigeraandSitticus pubescens) avoid slipping when accelerating. Both species differed in the relative contribution of leg pairs to the jump.P. lanigeraaccelerated mainly with their long third legs, whereas their short fourth legs detached earlier. In contrast,S. pubescensaccelerated mainly with their long fourth legs, and their short third legs detached earlier. Because of the different orientation (fourth-leg tip pointing backward, third-leg tip pointing forward), the fourth-leg tarsus pushed, whereas the third-leg tarsus pulled. High-speed video recordings showed that pushing and pulling was achieved by different attachment structures. InP. lanigera, third-leg feet made surface contact with setae on their distal or lateral claw tuft, whereas fourth-leg feet engaged the proximal claw tuft, and the distal tuft was raised off the ground.S. pubescensshowed the same division of labour between proximal and distal claw tuft for pushing and pulling, but the claw tuft contact lasted longer and was more visible in the fourth than in the third legs. Experimental ablation of claw tufts caused accelerating spiders to slip, confirming that adhesion is essential for jumps from smooth substrates.

Many hemipteran bugs can jump explosively from plant substrates, which can be very smooth. We therefore analysed the jumping performance of froghoppers (Philaenus spumarius,Aphrophoridae) and leafhoppers (Aphrodes bicinctus/makarovi,Cicadellidae) taking off from smooth (glass) and rough (sandpaper, 30 µm asperity size) surfaces. On glass, the propulsive hind legs ofPhilaenusfroghoppers slipped, resulting in uncontrolled jumps with a fast forward spin, a steeper angle and only a quarter of the velocity compared with jumps from rough surfaces. By contrast,Aphrodesleafhoppers took off without their propulsive hind legs slipping, and reached low take-off angles and high velocities on both substrates. This difference in jumping ability from smooth surfaces can be explained not only by the lower acceleration of the long-legged leafhoppers, but also by the presence of 2–9 soft pad-like structures (platellae) on their hind tarsi, which are absent in froghoppers. High-speed videos of jumping showed that platellae contact the surface briefly (approx. 3 ms) during the acceleration phase. Friction force measurements on individual hind tarsi on glass revealed that at low sliding speeds, both pushing and pulling forces were small, and insufficient to explain the recorded jumps. Only when the tarsi were pushed with higher velocities did the contact area of the platellae increase markedly, and high friction forces were produced, consistent with the observed jumps. Our findings show that leafhoppers have special adhesive footpads for jumping from smooth surfaces, which achieve firm grip and rapid control of attachment/detachment by combining anisotropic friction with velocity dependence.