A/Prof. Ajay Narendra1, Mr Pranav Joshi1, Dr Daniele Liprandi2, Dr Gregory Anderson3, Dr Jonas Wolff1,2

1Macquarie University, Australia, 2University of Greifswald, Greifswald, Germany, 3Queensland Museum, South Brisbane, Australia

Biography:

Ajay Narendra is an Associate Professor of Invertebrate Neuroethology with an interest in spatial navigation and design of sensory systems at the limits of size. His group also specialises in working with nocturnal insects/spiders where they use behavioural, physiological and pharmacological tools to investigate the neural basis of navigation.

Abstract:

Predator-prey interactions are a crucial driver in selection for kinematic performance in animal movements, pushing the limits of extreme speed and power. In small animals, physiological limitations to the evolution of power density (i.e., the rate of force production per actuator mass) have been repeatedly overcome by mechanisms of elastic energy storage in external devices that release energy at much higher rates than muscles. Typically, spiders avoid hunting ants since ants are heavily defended, with numbers, morphological structure and chemicals. The nocturnal spring-snare spiders (Theridiidae: Propostira sp.) found in Australia's tropical rainforests live in association with green tree ants (Oecophylla smaragdina), on which they feed exclusively. We will show how these spiders overcome dangerous predators by isolating and immobilising individual ants from foraging trails. The spiders construct a unique snare that lures ants and a fan-shaped array of tension lines acting as spring actuators, propelling ants into the core web at accelerations close to 1400m/s². The snare consists of a dense, regularly shaped cone-like foot structure that specifically attracts nearby O. smaragdina ants. The spider constructs serial arrangements of tension lines, and small pre-strains of the silk are sufficient to overcome the strong attachment forces of the ant to reach power densities of up to two megawatts per kilogram actuator mass, this surpassing the performance of other spring-actuated systems.