The hemiellipsoid neuropil and its corresponding cell cluster. A to C: 3-D reconstructions of the hemiellipsoid neuropil (HN) of the left brain hemisphere in different orientations. In A and B the cell cluster 5 and in C the HN is displayed semitransparently, to show the subjacent structures. D: Silver impregnation of a microtome slice is shown, and the boxed areas are pictured in higher magnification in G and J, making the orientation of fibers within the various layers visible. Note that in E, the horizontal vibratome section with immunohistochemical labeling against SIFamide (SIF; black) is obtained from another animal, but in a similar section plane. F: Horizontal vibratome section triple labeled against cell nuclei (NUC; blue), synapsin (SYN; red) and allatostatin-like (AST; green) immunoreactivity. The boxed area in F is illustrated in higher magnification in H, to present the synaptic interconnections within the second intermediate layer, in a single-channel view for anti-synapsin (white) immunoreactivity. Abbreviations: 5, cell cluster 5; Cap, Cap neuropil; CO1, outer or 1st core neuropil; CO2, inner or 2nd core neuropil; IL, intermediate layer; IL1 and IL2, outer or 1st and inner or 2nd intermediate layer (subunits of the IL).