Jumping mechanisms in dictyopharid planthoppers (Hemiptera, Dicytyopharidae)

Abstract

The jumping performance of four species of hemipterans belonging to the family Dictyopharidae, from Europe, South Africa and Australia, were analysed from high-speed images. The body shape in all was characterised by an elongated and tapering head that gave a streamlined appearance. The body size ranged from 6 to 9 mm in length and from 6 to 23 mg in mass. The hind legs were 80-90% of body length and 30-50% longer than the front legs, except in one species in which the front legs were particularly large so that all legs were of similar length. Jumping was propelled by rapid and simultaneous depression of the trochantera of both hind legs, powered by large muscles in the thorax, and was accompanied by extension of the tibiae. In the best jumps, defined as those with the fastest take-off velocity, Engela minuta accelerated in 1.2 ms to a take-off velocity of 5.8 m s(-1), which is the fastest achieved by any insect described to date. During such a jump, E. minuta experienced an acceleration of 4830 m s(-2) or 490 g, while other species in the same family experienced 225-375 g. The best jumps in all species required an energy expenditure of 76-225 μJ, a power output of 12-80 mW and exerted a force of 12-29 mN. The required power output per mass of jumping muscle ranged from 28,000 to 140,200 W kg(-1) muscle and thus greatly exceeded the maximum active contractile limit of normal muscle. To achieve such a jumping performance, these insects must be using a power amplification mechanism in a catapult-like action. It is suggested that their streamlined body shape improves jumping performance by reducing drag, which, for a small insect, can substantially affect forward momentum.