The Mechanical Power Output of A Tettigoniid Wing Muscle During Singing and Flight

Abstract

ABSTRACT The mesothoracic wings of tettigoniid insects are used in song production and flight; the metathoracic wings in flight only. In Neoconocephalus triops the wing stroke frequency during flight is about 25 Hz ; the frequency during singing about 100 Hz. The twitch duration of mesothoracic, first tergocoxal (Tcxl) wing muscles is only about one-half the duration of the upstroke or downstroke portion of the wing cycle. During tethered flight the Tcxl muscles are activated on each cycle with short bursts of action potentials, each burst typically containing four action potentials. Activating the muscles with brief, tetanizing bursts increases the duration of muscle activity and the mechanical power output per wing cycle above that obtainable with single twitch contractions of the muscle. The mechanical power output was determined for mesothoracic Tcxl muscles undergoing sinusoidal length change and stimulated phasically in the length cycle. At 25 Hz, the power at optimum muscle strain and optimum stimulus phase was 5 Wkg-1 at 30 °C for muscles activated with a single stimulus per cycle and about 33 W kg-1 for muscles activated with bursts of stimuli in the normal pattern of flight. The maximum power output at 100 Hz, the singing frequency, was 18 W kg-1. This was achieved with a single stimulus per wing cycle. From published values of oxygen consumption by tettigoniids during singing, it is concluded that the efficiency of conversion of metabolic to mechanical power during singing is about 3 %.