ORGANIZATION OF THE ANTENNAL MOTOR SYSTEM IN THE SPHINX MOTH MANDUCA-SEXTA

The antennae of the sphinx moth Manduca sexta are multimodal sense org ans, each comprising three segments: scape, pedicel, and flagellum. Ea ch antenna is moved by two systems of muscles, one controlling the mov ement of the scape and consisting of five muscles situated in the head capsule (extrinsic muscles), and the other system located within the scape (intrinsic muscles) and consisting of four muscles that move the pedicel. At least seven motoneurons innervate the extrinsic muscles, and at least five motoneurons innervate the intrinsic muscles. The den dritic fields of the antennal motoneurons overlap one another extensiv ely and are located in the neuropil of the antennal mechanosensory and motor center. The density of motoneuronal arborizations is greatest i n the lateral part of this neuropil region and decreases more medially . None of the motoneurons exhibits a contralateral projection. The cel l bodies of motoneurons innervating the extrinsic muscles are distribu ted throughout an arching band of neuronal somata dorsal and dorsolate ral to the neuropil of the antennal mechanosensory and motor center, w hereas the cell bodies of motoneurons innervating the intrinsic muscle s reside mainly among the neuronal somata situated dorsolateral to tha t neuropil.