Composition and substrate-dependent strength of the silken attachment discs in spiders

Abstract

Araneomorph spiders have evolved different silks with dissimilar material properties, serving different purposes. The two-compound pyriform secretion is used to glue silk threads to substrates or to other threads. It is applied in distinct patterns, called attachment discs. Although ubiquitously found in spider silk applications and hypothesized to be strong and versatile at low material consumption, the performance of attachment discs on different substrates remains unknown. Here, we analyse the detachment forces and fracture mechanics of the attachment discs spun by five different species on three different substrates, by pulling on the upstream part of the attached thread. Results show that although the adhesion of the pyriform glue is heavily affected by the substrate, even on Teflon it is frequently strong enough to hold the spider's weight. As plant surfaces are often difficult to wet, they are hypothesized to be the major driving force for evolution of the pyriform secretion.

Hunting with sticky tape: functional shift in silk glands of araneophagous ground spiders (Gnaphosidae)

“…In attachment discs of both web-building and wandering spiders, PI silk breaks before detachment for surfaces with moderate to high polarity (Grawe et al, 2014;Wolff et al, 2015). This means that the adhesion of the glue coat exceeds its strength in these cases.…”

A theoretical-numerical model for the peeling of elastic membranes

“…Adhesion is a topic that has attracted great interest in the mechanics community in recent years. The field of biological materials has allowed to exploit theories for adhesion formulated in the past years (Kendall, 1975;Maugis, 1992;Palacio and Bhushan, 2012) and has stimulated the formulation of novel theories and models for complex problems emerging from bio-mimetics (Lai et al, 2009;Carbone et al, 2011;Prokopovich and Starov, 2011;Brodoceanu et al, 2016;Cutkosky, 2015), from biomechanics (Arzt et al, 2003;Tian et al, 2006;Grawe et al, 2014;Labonte and Federle, 2016) or even from nano-mechanics (Rakshit and Sivasankar, 2014;Mo et al, 2015).…”

Phylogenetic position and composition of Zygiellinae andCaerostris, with new insight into orb-web evolution and gigantism

“…Moreover, because orb webs are made with nature's toughest biomaterial and covered with glue, orb weavers are central objects of biomaterial research (e.g. Hayashi & Lewis, ; Agnarsson et al ., ; Swanson et al ., ; Vollrath & Porter, ; Agnarsson, Kuntner & Blackledge, ; Sensenig, Agnarsson & Blackledge, ; Sahni, Blackledge & Dhinojwala, ; Blackledge et al ., ; Vasanthavada et al ., ; Grawe, Wolff & Gorb, ; Stellwagen, Opell & Short, ). Hence, a solid phylogenetic understanding of orbicularian spiders would benefit all of these biological disciplines.…”