The brains and higher sensory centers. A: A horizontal confocal optical section of the whole head region. B: A sagittal histological section of the head to show the brain subdivisions. The white dotted line covered with pseudo-green color indicates the position of the mushroom body-like structure in a section stained with hematoxylin-eosin. The dotted lines indicate optical cutting sites for confocal microscopy. C: The direct sensory pathways from tuft type cilia to the mushroom body, a sagittal section of the head. D-F: The nuclei distribution and neuropil structure. Horizontal optical sections viewed from the dorsal side at the level of the neuropil of the mushroom body (encircled with dotted red line). G-I: The highly mingled axons from small mushroom body neurons (G), the brain neuropil (H), and more ventral region (I). Nuclei stained with DAPI and tubulin positive fibers to show the distinct neuropils and axonal bundle patterns. The horizontal optical section series of confocal microscopy viewed from the dorsal (globuli cluster level) to ventral side. Arrowheads indicate the axonal fiber patterns running from dorsal to ventral, and to connectives. The phalloidin (actin) was used for counterstaining of neural fibers and muscles. br, brain; cen, central neuropil; co 1–5, connective to ventral nerve cords; ent, sensory axon entry region of the neuropil; pt, patch type cilia; mbc, mushroom body cells; np, neuropil; tt, tuft type cilia. Scale bar in A, D-I: 100 μm; B: 50 μm; C: 20 μm.