Central branchings of three sensory axons from a moth ear (Agrotis segetum, Noctuidae)

The central branchings of the sensory neurons in the noctuid moth ear have been investigated by introducing cobalt chloride through the cut ends of their axons. Three sensory axons stained, corresponding to the two auditory neurons (A cells) and the B neuron. The three axons were identified using physiological criteria. All three cells share the same basic morphology. Their axons divide into anterior and posterior branches, which contain numerous side branches. Their profiles lie ipsilateral, but A₁ gives off some fine side branches that cross the midline. The profiles of A₁ and B extend throughout all three thoracic ganglia, occupying a ventral, medial position. The branchings of A₂ remain within the meso- and metathoracic ganglia occupying a more dorsal and lateral position. We compare our results with those of an earlier anatomical study, and discuss them in relation to described interneurones and to behaviour