Enhancer trap expression is firstdetected in stage 9 in the procephalic lobe and in the ventral neurogenicregion. EcollacZ is expressed throughout embryogenesis in a segmentallyrepeating pattern in the nervous system . Expression is also detected intracheal placodes and in sense organs. Staining is observed in the labial,maxillary, and mandibular lobes, persists, and is associated with theantenno-maxillary complex, the hypophysis, the larval labral sense organ,and the clypeolabrum in mature embryos. In third instar larvae, stainingis strong in the cerebral hemispheres and in the ventral nerve cord. Inthe eye-antennal disc, expression is found in developing ommatidiaposterior to the morphogenetic furrow and at a stronger intensity at thefurrow. In adults, EcollacZ expression is seen in several neuronal nuclei ofthe brain and thoracic ganglion, and in cells of the retina, proboscis,and antenna. The sensilla that stain in the proboscis are thought to betaste neurons.