J Comp Physiol (1982) 149:163-177

1. The structure of one class of giant tangential neurons in the lobula plate of Calliphora, the `Vertical System (VS)' has been investigated by light microscopy. Different staining and reconstruction procedures were employed to ensure that all existing VS-neurons are revealed. 2. There are 11 VS-cells in a characteristic, and constant arrangement (Fig. 2). Each cell covers a particular area of the lobula plate, i.e., a distinct area of the retinotopic input array (Table 2), and therefore has a distinct receptive field. 3. Although VS-cells in general tend to occupy the posterior surface of the lobula plate, only three of them (VS 2-VS 5) reside exclusively in this layer. The other cells (VS1 and VS6-VS10) have bistratified dendritic arborizations (Fig. 6), whose dorsal parts are apposed to the anterior surface of the lobula plate. 4. The arrangement, territory and stratification of any given VS-cell is largely invariant in different individuals, whereas the branching pattern may vary considerably (Fig. 3). 5. The present results provide the framework for physiological studies of the role of individual VScells in movement perception, and their involvement in the control of particular locomotor behaviour.