Tracheal gases, respiratory gas exchange, body temperature and flight in some tropical cicadas

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 V·O2 to about 16 times the resting level. During wing-flapping in fixed flight, V·O2 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, FO2 in the thoracic air sacs remains near 17 % and FCO2, near 3 %. During non-flapping warm-up, FO2 falls to as low as 1 % and FCO2 rises to as high as 21 %. Thus, gas exchange may limit the rate of warm-up. When wing-flapping commences, FO2 and FCO2 quickly return to near resting levels, presumably as a result of auto ventilation. The interspecific regression of V·O2 on mass for three species of cicadas at 23-24°C has a slope of 0·89 and a 1-g intercept of 0·63 ml h−1.