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Acknowledgements We are grateful for the guidance and supervision of Judy Cebra-Thomas and William Gresh during the course of this experiment. We extend additional thanks to Judy Cebra-Thomas for figures 1-5 used in this paper.   References Alberts, B. et al. 2002. Molecular Biology of the Cell, 4th ed. Garland Science, 1199-1210. Condic, M.L., D. Fristrom and J.W. Fristrom. 1990. Apical cell shape changes during Drosophila imaginal leg disc elongation: A novel morphogenetic mechanism. Development 111:23-33. Gates, J., Thummel, C.S. 2000. An enhancer trap screen for ecdysone-inducible genes required for Drosophila adult leg morphogenesis. Genetics 156:1765-1776. Gilbert, S.F. 2003. Developmental Biology, 7th ed. Sunderland: Sinauer Associates, 584-588. Kozlova T., Thummel, C.S. 2003. Roles for ecdysone signaling during Drosophila mid-embryonic development. Science 301:1911-1914. Metamorphosis: Drosophila imaginal discs. Lab manual: 80-84. Riddiford, L.M. Hormones and Drosophila development, in: Bate, M., Martinez-Arias, A. (eds.), The Development of Drosophila melanogaster, Vol. II, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 899-939. Ward, R.E., Reid, P., Bashirullah, A., Avino, P., Thummel, C.S. 2003. GFP in living animals reveals dynamic developmental responses to ecdysone during Drosophila metamorphosis. Dev. Biol. 256:389-402.