Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom; Zoology Department, University of Cape Town, Private Bag X3, Rondebosch, 7701, Cape Town, South Africa
Burrows, M., Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom; Picker, M.D., Zoology Department, University of Cape Town, Private Bag X3, Rondebosch, 7701, Cape Town, South Africa
Pygmy mole crickets live in burrows at the edge of water and jump powerfully to avoid predators such as the larvae and adults of tiger beetles that inhabit the same microhabitat. Adults are 5-6 mm long and weigh 8mg. The hind legs are dominated by enormous femora containing the jumping muscles and are 131% longer than the body. The ratio of leg lengths is: 1:2.1:4.5 (front:middle:hind, respectively). The hind tarsi are reduced and their role is supplanted by two pairs of tibial spurs that can rotate through 180deg. During horizontal walking the hind legs are normally held off the ground. Jumps are propelled by extension of the hind tibiae about the femora at angular velocities of 68,000deg s-1 in 2.2 ms, as revealed by images captured at rates of 5000 s-1. The two hind legs usually move together but can move asynchronously, and many jumps are propelled by just one hind leg. The take-off angle is steep and once airborne the body rotates backwards about its transverse axis (pitch) at rates of 100 Hz or higher. The take-off velocity, used to define the best jumps, can reach 5.4 ms-1, propelling the insect to heights of 700mm and distances of 1420mm with an acceleration of 306g. The head and pronotum are jerked rapidly as the body is accelerated. Jumping on average uses 116 μJ of energy, requires a power output of 50mW and exerts a force of 20mN. In jumps powered by one hind leg the figures are about 40% less. © 2010. Published by The Company of Biologists Ltd.
animal; animal behavior; article; biomechanics; Gryllidae; hindlimb; histology; locomotion; motor activity; physiology; anatomy and histology; locomotion; Animals; Behavior, Animal; Biomechanics; Gryllidae; Hindlimb; Locomotion; Motor Activity; Cicindelidae; Coleoptera; Hexapoda; Insectivora; Orthoptera; Tridactylidae; Animals; Behavior, Animal; Biomechanical Phenomena; Gryllidae; Hindlimb; Locomotion; Motor Activity
