Fig. 6. Antennal lobe development in Drosophila. In the wild type, the projection neurons (blue) enter the lobe at the pupal stages before sensory afferents arrive in the lobe (A). (B) Ato-lineage neurons (green) arrive at the lobe at 20 hours APF and remain at the periphery in close association with glial cells (red). (C) Other sensory neurons (purple) arrive later. (D) Between 30 and 60 hours APF, glomerular formation occurs. Sensory neurons invade the nascent lobe; projection neurons arborize at glomerular sites and glial processes ensheath the developing glomeruli. (E) In ato¹/Df(3R)p¹³ animals, the residual sensory neurons enter the lobe but do not pattern glomeruli. These interneurons, although present in the lobe, do not target specific glomeruli and the glial cells produce ectopic branching within the lobe.