MOTOR SUPPLY OF THE DORSAL LONGITUDINAL MUSCLES .1. HOMONOMY AND ONTOGENY OF THE MOTONEURONS LOCUSTS (INSECTA, CAELIFERA)

The neural supply of the dorsal longitudinal muscles in successive seg ments from the prothorax to the pregenital abdomen of adult and larval instar locusts (Locusta migratoria and Schistocerca gregaria) has bee n studied. Stainings have also been carried out for embryos. The whole complement consists of three muscles, of which one or both of the sma ller ones degenerate in the pterothoracic segments during early imagin al life. Based on morphological criteria, several motoneurone types ca n be distinguished. The neural set is almost identical for all segment s, independent of the general organization of each segment. At about 6 5% of embryogenesis, all neurone types can be identified with respect to soma position and basic features of the central branching pattern. By the end of embryogenesis, a dendritic pattern is esl tablished whic h resembles the adult pattern in all major aspects. The reiteration of homonomous elements suggests that they form part of the basic segment al neural Bauplan generated early in embryogenesis. This study of musc les and motoneurones forming identifiable, reiterated neuromuscular un its can serve as a segmental matrix for a comparative study comprising other phylogenetic groups of the Tracheata.