Tracheal Gases, Respiratory Gas Exchange, Body Temperature and Flight in Some Tropical Cicadas

Abstract

Fidicina mannifera Fab. (mass 3 g) can fly at a body temperature of 22°C but take-off is usually preceded by an endothermic warm-up that elevates Tth to 28 °C or higher. Warm-up is accompanied by slow, almost imperceptible, wing movements, gentle abdominal pumping and an increase in VOO2 to about 16 times the resting level. During wing-flapping in fixed flight, VOO2 increases explosively to about 70 times the resting level, and thoracic temperature rises to about 33°C. Wing-beat frequency increases with Tth. Between 25 and 34°C the mean wing-beat frequency is about 37 Hz. F. mannifera does not maintain free flight, or wing flapping in fixed flight, for more than about 100 s. Flight is supported aerobically, and we infer that exhaustion is related to depletion of substrate in the flight muscles. The volume of the tracheal system of F. mannifera is about 45% of total body volume. At rest, FCC2 in the thoracic air sacs remains near 17% and FCOCO2, near 3%. During non-flapping warm-up, FOO2 falls to as low as 1 and FCOCO2 rises to as high as 21%. Thus, gas exchange may limit the rate warm-up. When wing-flapping commences, FOO2 and FCOCO2 quickly return near resting levels, presumably as a result of auto ventilation. The interspecific regression of VOO2 on mass for three species of cicadas 23–24°C has a slope of 0.89 and a 1-g intercept of 0.63 mlh−1.