The Design, Diversity, and Performance of Viscous Capture Threads Produce by Araneoid Orb-weaving Spiders

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

This project examines the design and function of viscous capture threads that are found in orb-webs produced by over 4,000 species of spiders. These sticky threads are formed of small adhesive droplets suspended on elastic fibers. Studies determine: 1. What adhesive forces contribute to droplet stickiness, 2. How these forces are recruited by fibers in a manner that resists crack propagation, 3. How droplet size, plasticity, and spacing optimize thread adhesion, 4. How well threads with different droplet profiles hold insect surfaces of different textures, and 5. How well orb-webs with different capture thread characteristics retain insects. This is done by: 1. Measuring how threads that have different droplet features stick to surfaces of different widths and textures, 2. Developing models that describe thread performance, 3. Conducting a survey and comparative analysis of the features of threads and orb-webs produced by many spider species, and 4. Measuring the time that insects are retained by orb-webs that have different capture thread features. These complementary approaches explain how viscous thread operates as an integrated adhesive system that recruits the compound adhesion of discrete units and resists crack prorogation, a set of serious challenges to both natural and manufactured adhesive systems. The principles and insights from these studies will help materials scientists develop new products and applications. These studies also show how capture thread design enhances prey capture by orb-weaving spiders and how it may facilitate prey specialization. These are important issues, as spiders are key predators in natural ecosystems and are receiving increasing attention as agents of biological insect control. Educational exercises are developed that involve grade school and high school students in field and laboratory studies that use microscopes, digital cameras, computer program, and simple, homemade instruments to collect and analyze data on the features of spider orb-webs and their threads.