The synaptic connectivity in each compartment are shown as arrows whose width is indicative of the number of synapses connecting the corresponding cell types. The arrows are color-coded as follows: DANs, green; MBONs with dendrites in the α1, α2 and α3 compartments, purple; the feedforward MBON-γ1pedc>α/β, dark blue; the feedforward MBON-β1>α, magenta; DPM, brown; and APL, light blue. Arrowheads indicate the main presynaptic sites of each neuron type. The names of cell types (shown in the rectangles with rounded corners) are color coded to reflect the major neurotransmitter of the cell: black, dopamine; orange, acetylcholine; green, glutamate; blue, GABA. The transmitter for MBON-α2sp is unknown (name is shown in grey), and for DPM (name shown in brown) is 5HT, GABA and the neuropeptide amnesiac. The correspondence of number of connections and line thickness is as follows: no line is shown when there are less than five connections; five connections, 2 pt line; 50 connections, 4 pt line; 15000 connections, 35 pt line; with line widths interpolated between these values using a log scale. Precise numbers can be found in the Tables 2–8 and Supplementary file 1. For some connections, such as the connections to and from KCs of APL, DPM, MBON-γ1pedc>α/β, MBON-β1>α and KCs, we have pooled the data from all three α-lobe compartments and present them in the lower rectangle labeled α lobe. We similarly pooled data on synapses between MBON-γ1pedc>α/β and MBON-β1>α and from MBON-γ1pedc>α/β to APL that was derived from counts in the α2 and α3 compartments. When more than one cell of a given type is present, such as the two MBON-α3 cells, the synapse counts for each cell have been added in determining line widths. The connection from MBON-γ1pedc>α/β to MBON-α1 is shown as a faint arrow because the EM reconstruction failed to identify MBON-γ1pedc>α/β in the α1 compartment (see text), although the presence of its arbors is indicated by light level data (Aso et al., 2014a).