Metabolic Rate and Body Temperature in Singing Katydids

The oxygen uptake of the katydids Neoconocephalus robustus and Euconocephalus nasutus is about 0.03-1.5 ml O₂ h⁻¹ g⁻¹ at rest. During the warm-up that precedes stridulation and during stridulation this rate increases to 18.4 ml O₂ h⁻¹ g⁻¹ (maximum 26.4) in Euconocephalus and to 15.8 ml O₂ h⁻¹ g⁻¹ (maximum 19.5) in Neoconocephalus. Oxygen uptake during stridulation is 1.5-1.9 ml O₂ min⁻¹ per gram active muscle, a value similar to that of wing muscle of other insects in flight. The thorax temperature 'increases during warm-up and stridulation. Cooling that occurs when singing ceases is not a simple exponential function. Metabolic rates calculated from cooling curves are lower than measured values; we suggest they are lower because the rate of heat loss is about 23% greater during singing because heat is convected by wing movement. On the basis of measurements of abdominal temperatures we suggest that about 40% of the heat produced by the thorax is transferred to the abdomen and lost via this avenue.