Spider WebsBehavior, Function, and Evolution

Spider WebsBehavior, Function, and Evolution

William Eberhard

Print publication date: 2021

ISBN: 9780226534602

Publisher: University of Chicago Press

Abstract

Spider silk proteins almost all evolved from a single ancestral “spidroin” gene that later multiplied in diverse forms. The strongest spider silk combines extraordinary extensibility and toughness, and the viscoelastic nature of draglines allows a web to absorb sudden stresses from prey without breaking or allowing the prey to bounce off the web. Behavioral mechanisms (some as yet poorly understood) are described for the initiation and termination of lines, including conversion of silk from an aqueous liquid, how some lines are made adhesive, and how the spiders themselves nevertheless avoid adhering to their own webs. There is previously unsuspected diversity in the chemical and mechanical properties of lines in different species, different glands, and even the silk from a given gland in a given individual spider. Detailed studies reveal that previous simplistic accounts were inadequate; inter- and intra-specific diversity abounds in the silk glands, the droplets of glue on sticky lines, the attachment discs fastening lines to each other, and the chemical and mechanical properties of the lines themselves. Multiple morphological and behavioral traits are crucial for building webs, including spinneret muscles, positions of silk gland spigots, and behavioral and morphological traits that reduce adhesion to their own webs.