The Structure and Function of the Prothoracic Spine of the Desert Locust, Schistocerca Gregaria ForskÅl

1. The prothoracic sternal spine of Schistocerca is described. The second paired nerve innervates the sensilla of the sternum, coxae, and femora, and in subimaginal stages supplies chordotonal organs registering movement of the cervical membrane. Each nerve fibre serves the axons of several sensilla. 2. When the sensilla are waxed, control of the legs is disturbed. 3. When the prothoracic ganglion is isolated from the CNS stimulation of the sensilla produces complex, oriented, reflex cleaning movements by the legs. 4. Recordings were made from nerve 2 and from the commissures. Co-ordination is mainly segmental; the signal in the commissures is much reduced. At normal levels of stimulation there is no activity in nerve 2 unless several sensilla are excited. 5. Among related genera there is some correlation between manipulative ability and the number of sensilla on the spine. It is suggested that these sensilla contribute to the co-ordination of movements of the front legs.