HOMONOMIES WITHIN THE VENTRAL MUSCLE SYSTEM AND THE ASSOCIATED MOTONEURONS IN THE LOCUST, SCHISTOCERCA-GREGARIA (INSECTA, CAELIFERA)

To understand the segmental reiteration of an insect, the serially arr anged neuromuscular system of the locust, Schistocerca gregaria, is st udied. The ventral muscle system is chosen and its motoneuronal supply is described in the thoracic and pregenital segments. In general, rep etitively arranged, similar sets of motoneurons (MNs) supply the ventr al muscles of these segments. Common criteria of both topology of musc les and neural features (nerve branches and motoneuronal supply) sugge st possible homonomies of the ventral longitudinal muscles and ventral diaphragm of the thoracic and abdominal system. Based on a segment-by -segment analysis, muscle topology and motor supply match, in most ins tances. There are, however, cases where such a parallelism is missing. In a particular case the supply of apparently homonomous muscles shif ts from one set of MNs to another. In another case, putatively equival ent MNs of different ganglia supply morphologically different muscle s tructures in the adult animal. Therefore, it becomes apparent that mus cles and their supplying MNs are, in principle, independent elements w hich might be subjected autonomously to ontogenetic processes. As a co nsequence, in the search for the basic segmental Bauplan depending on homonomous structures, muscles and MNs have to be regarded as separate entities.