FOREWING MOVEMENTS AND INTRACELLULAR MOTONEURON STIMULATION IN TETHERED FLYING LOCUSTS

A new optoelectronic method was used for the measurement of wing movem ents in tethered flying locusts, The method is based on laser light co upled into a highly flexible optical fibre fastened to a forewing. A d ual-axis position-sensing photodiode, aligned to the wing hinge, revea led the flapping, i.e. up-down movement, and lagging, i.e. forward-bac kward movement, of the wingtip as indicated by the emitted light, Meas urements were combined with electromyographic recordings from flight m uscles and with intracellular recording and stimulation of flight moto neurones. Compared with muscle recordings, intracellular recordings sh owed an increase in the variability of motoneurone activity, Stimulati on of flight motoneurones reliably caused distinct effects on wing mov ements, Inhibition of elevator (MN83, MN89) activity led to a decrease in the amplitude of the upstroke. Inhibition of depressor (MN97) acti vity reduced the amplitude of the downstroke and sometimes stopped fli ght behaviour, An increase in MN97 activity caused a reduction in the extent of the upward movement and prolonged the flight cycle.