Fig. 1. Survey of the spatial organisation of the embryonic head and brain neuroblasts at stage 11. Semi-schematic drawing showing a lateral view of a (A) wholemount and (B) a ventral view of a flat preparation, in which the head capsule has been dorsally opened. The pregnathal (light grey) and gnathal (dark grey) head region is indicated in relation to the engrailed expression pattern (dark blue). (C) Left half of a head flat preparation, including the complete pregnathal NB pattern. NBs are named according to their assignment to the trito- (T), deuto- (D) and protocerebrum (P), based on the reconstruction of segmental borders [indicated by red lines; for details see Urbach and Technau (Urbach and Technau, 2003a)]. Protocerebral NBs are subdivided into an anterior (Pa), central (Pc) and posterior (Pp) group (indicated by blue broken lines), roughly reflecting their origin from distinct mitotic domains (see Fig. 5 and Table 1). Each of the protocerebral groups, as well as the deuto- and tritocerebral NBs, is further subdivided into a dorsal (d) and a ventral (v) subgroup (indicated by yellow line) based on vnd expression [except NB Dd5, which co-expresses msh and is therefore attributed to the dorsal deutocerebrum (Urbach and Technau, 2003a)]. Within each subgroup, NBs are numbered from anterior to posterior and from ventral to dorsal. a, d, p, v: anterior, dorsal, posterior, ventral. as, is, las, mds, mxs: antennal, intercalary, labial, mandibular and maxillary en stripe, respectively. cl: en expression in the clypeolabrum. hs: en head spot. AN, IC, LA, MD, MX, PT, 1.AB: antennal, intercalary, labial, mandibular, maxillary, prothoracic and first abdominal segments, respectively. CF: cephalic furrow. CL: clypeolabrum. dML: dorsal midline. FG: foregut. OA: Bolwig organ/optic lobe anlagen. vML: ventral midline.