Fig. 6.

Factors affecting the strain registration and their impact in different setups. a Integration of deformation: a strain gauge covering the lyriform organ HS8 (right inset to scale) registers the sum of the slit deformation remaining after the attachment of the gauge divided by wire length. The inset depicts the selected strain gauge (yellow) covering the lyriform organ (black: lyriform organ HS8, 1. 7: slit numbers; to scale). In the main figure, the vertical distance between the slits (bold black horizontal lines) is expanded. Yellow vertical lines I…IV: wires of the gauge (comp. inset). Blue curves: deformation of the slits (λ) obtained by FEM and interferometry (λ = deformation of slit/(6.57 × 10^–4 × length of slit) [m]; for details, see Hößl et al. 2009; Schaber et al. 2012). b Joint stiffness during cyclic triangular anteroposteriad deflection (upper arrow) at the metatarsus tip (tarantula; leg angle α = 160°, Fig. 1). F force; β deflection (anteriad: β > 0, for orientation see Fig. 1; 1 mm ≡ 3.5°; rate 0.1°/s; see material and methods). c, d Delineating visco-elastic properties using a standard linear solid. Viscosities can be found both at the joint (see b) and in the cuticle and the strain gauge. The examples describe extreme situations to identify the dominating viscosities. c The quick step deflection β at the leg tip causes an immediate rise in force. It compresses the cuticle spring (l) as the viscous element is rigid. While maintaining the deflection, the viscous element at the joint gives in. The two springs in series now in effect are less stiff than each single spring and the force drops. Correspondingly, the initial compression of the cuticle spring is reduced. This is the behavior observed in our measurements. d Alternative: the initial deflection compresses the joint and viscosities in the cuticle hamper its initial deformation. The joint is slowly compressed, while the external deflection is maintained. This is not observed (red brackets). β₀, F₀, l₀: starting values