P{Or83b-Gal4} transcriptional activation begins shortly before eclosion. P{Or83b-Gal4} (third chromosome)/UAS-EGFP transheterozygous antennae are shown at the designated times APF. Panels (A) through (E) display the antennal structures, while panels (F) through (J) show expression of enhanced green fluorescent protein (EGFP). At 78 h APF, the head bristles were fully pigmented, pigmentation was beginning in the abdominal bristles, and GFP expression was not yet visible in the third antennal segment (A, F). The first hints of GFP expression were found at 82 h APF (arrowhead; B, G). At 85 h APF, GFP expression is beginning to spread, but it is not yet established throughout the third antennal segment (C, D). By 92 h APF, GFP is detected widely throughout the third antennal segment (D) and (I). GFP expression was even more pronounced after eclosion E and (J).