Efferent system of the lateral ocellus in the dragonfly: Its relationships with the ocellar afferent units, the compound eyes, and the wing sensory system

Abstract

1. The activity of lateral ocellar nerve fibres of the dragonfly was studied with special reference to the activity of efferent fibres. 2. Afferent and efferent impulses were recorded from the distal and proximal cut-ends of the ocellar nerve using suction electrodes. The lateral ocellar nerve was found to contain, at least, two kinds of afferent (one large and the other small) and three kinds of efferent (one large and the others small) fibres (Fig. 7). 3. The large efferent fibre was activated by illumination of the compound eyes, and also during wingbeat (Figs. 4, 5, and 6). 4. In the intact ocellar nerve, the large afferent fibre was also activated during wing-beat, but the evoked discharge was inhibited by illumination (Fig. 2). The result suggests an excitatory pathway from the efferent fibre to the large afferent within the distal synaptic region of the ocellar nerve. 5. The impulse activities of wing sensory nerves were recorded relative to the position and movement of the wings (Fig. 10). 6. Electric stimulation of a wing sensory nerve produced bursting discharges in efferent fibres in both ipsi- and contra-lateral ocellar nerves (Fig. 11). It is probable that the efferent fibres are excited by input from sense organs in the wing's hinges.