The Effects of Temperature on Flight Muscle Potentials in Honeybees and Cuculiinid Winter Moths

Amplitudes of extracellular action potentials in indirect flight muscles of honey-bees and cuculiinid winter moths decline with decreasing muscle temperatures and fall suddenly to zero. Action potential durations increase with amplitude decline. Amplitudes at 11 °C are only 20% of values near 30°C in workers of Apis mellifera mellifera. They fall to zero at approx. 10°C. In the cuculiinid winter moth Eupsilia devia, amplitudes at 1°C are approx. 12% of values at 27°C. They fall to zero between 0 and 1°C. The duration of action potentials in bees and cuculiinid winter moths is about 7 ms at 27 °C and increases to 52 ms at 11 °C in bees and to 66 ms at 1°C in moths. The ratios of action potential rise time to fall time are about 1 at 27°C for bees and moths. They decrease to 0·45 at 11 °C in bees and to 0·56 at 1°C in moths. Results suggest that bees can heat flight muscles only if muscle temperatures are above 10°C, whereas cuculiinid winter moths can shiver with muscle temperatures near 0°C.