Influence of normal load on friction and projected contact area of arolia (A–C) and euplantulae (D–F) of <i>Carausius morosus</i> (n = 10 for each level).

<p>Dark grey boxes on the left of each plot depict the actual data at 1-1 mN and 4-2 mN normal load. Triangles within the light grey boxes indicate the position of the estimated mean of the differences together with corresponding 95% confidence interval as calculated with a paired t-test. Horizontal dashed lines indicate the zero difference line. For arolia, friction showed a slight trend to increase with normal load (A), but not contact area and kinetic shear stress (B and C). For euplantulae, friction, projected contact area and shear stress (friction per projected contact area) (D to F) significantly increased with normal load.</p

Experimental set-up and morphology of arolium and euplantulae.

<p>(A) Set-up for measuring adhesion, friction and contact area of single attachment pads. (B) Scanning electron micrograph (SEM) of the arolium of <i>Carausius morosus</i>. The dotted line indicates the adhesive contact zone. (C) Contact area of arolium, as recorded during a force measurement. (D) Image of (C) after binary conversion with the fuzzy threshold algorithm <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081943#pone.0081943-Huang1" target="_blank">[29]</a>. (E) SEM of the euplantulae (second tarsal segment). (F) Contact area of euplantulae during a force measurement (second tarsal segment). (G) Polygon drawn around the contact area for measuring the projected contact area. Scale bars are 200 (B–C) and 100 (D–F).</p

EndleinFederle_Data_PONE-D-15-22788

Raw data for all figures presented in the manuscript

Use of attachment organs in unrestrained stick insects (<i>Carausius morosus</i>) (A) standing upright and (B) hanging upside down on a smooth petridish.

<p>Insects were filmed from the side and the contact area of individual pads was recorded using reflected-light microscopy (see insets). Note that euplantulae were never in surface contact when insects were hanging upside down. Scale bars are 200 for insets and 1 mm for side views.</p

Morphology of the tarsus of <i>Carausius morosus</i>.

<p>(A) pre-tarsus with adhesive pad (arolium) between the pair of claws. (B) surface of the arolium contact area with folds running along the proximal-distal axis. (C) pair of euplantulae on the ventral side of the tarsus (second tarsal segment). (D)–(F) acanthae on the surface of the euplantulae. AR arolium, CL claw, EU euplantulae. Scale bars are (A) 200 , (B) 4 (C) 100 m, (D) 20 , (E) 1 , (F) 10 .</p

Data for figures 1 & 3

Relationship between shear force, adhesive force, peel angle, and crack propagation speed for the adhesive organs of stick insects (Carausius morosus

Results of single pad adhesion measurements at different pulling forces for arolia and euplantulae of <i>Carausius morosus</i>, all performed with a preload of 2 mN (n = 10 for each condition; meansd).

<p>Results of single pad adhesion measurements at different pulling forces for arolia and euplantulae of <i>Carausius morosus</i>, all performed with a preload of 2 mN (n = 10 for each condition; meansd).</p

Shear stress (friction per unit projected contact area) of a single pair of euplantulae of <i>Carausius morosus</i> plotted against the optical contrast of the contact area for three normal loads (n = 10 for each level).

<p>Inset shows an example of the euplantula contact zone at 1,2 and 4(from left to right). Large symbols indicate the mean contrast and shear stress for each normal load with the corresponding standard error of the mean.</p

Relationship between peak normal force and corresponding shear force along the (projected) axis of the leg for individual steps.

<p>Filled circles denote steps in which the arolium made visible surface contact, whereas steps with detached arolium are marked with open circles. Lines show standardised major axis regressions on both types of steps. In most steps where the adhesive pad made contact, the legs were pulling, whereas steps without visible arolium contact occurred mostly when legs pushed. The drawings illustrate the direction of the normal forces (<i>F</i>_<i>N</i>) and shear forces (<i>F</i>_<i>S</i>) and the presence or absence of adhesive pad contact (black or white filling of the pad).</p

Reflected-light microscopy images of the tarsal hairs in contact with the smooth surface.

<p>(A) side contact of the hairs (B) tiny droplets left on the surface after pull-off.</p