Figure 2. Higher-order visual and olfactory neuropils in M. stellatarum and D. elpenor.

Anterior (left) and posterior (right) view of 3D reconstructed central neuropils of the diurnal (a) and nocturnal (b) species. Higher-order sensory structures in colour, other neuropils in grey, remaining neuropil in light grey (c). Close-up of the anterior optic tubercle (visual). (d,e) Olfactory projections from the antennal lobes identified the lateral horn (d, blue line), and the olfactory input regions to the mushroom body calyx (calyx inner zone, (e). Lobula injections revealed visual input regions in the mushroom body calyx (e). Scale bars in (c–e) 100 μm. (f–h). Relative neuropil volumes of higher-order visual (f), olfactory (g) and multimodal (h) brain areas: grey (diurnal) and black (nocturnal) circles show individual measurements, shaded areas interquartile ranges and horizontal bars (colour code as in a,b) medians. Significance tests with Mann-Whitney-U test: *p < 0.05, **p < 0.01, ***p < 0.001. (i) The grade shift index (gsi) and the slope ratio (si). Colour as in Fig. 1. For full results and statistics see Supplementary Tables S1, S2.