Segmental and interganglionic projections from primary fibres of insect mechanoreceptors.

Projections of primary insect mechanoreceptor fibres in Locusta migratoria and Acheta domesticus are visualised with the cobalt intensification technique after axonal or dendritic filling with cobaltous chloride. Chordotonal proprioceptors of the locust mesothoracic thoracocoxal joint have typical segmental projections and more or less widespread interganglionic processes into the metathoracic, prothoracic and even suboesophageal ganglia. Similar observations can be made on locust abdominal chordotonal organs, from some of which all primary axons project into five preceding neuromeres or ganglia. From locust abdominal stretch receptors and cricket mechanosensitive sternal hairs single afferent axons extend through several ganglia. Locust campaniform sensilla and clavate hair projections of crickets terminate locally. It is concluded that many interganglionic primary afferents contribute to intersegmental control of motor coordination in insects.