Male E. simplicicollis change from female-like coloration to pruinose blue over the entire thorax and the first 7 abdominal segments through a predictable progression of color patterns. 17 stages were delineated in this study. The change occurs over a period of about 2 to 3 weeks in Gainesville, Florida. Males marked within a few hours of emergence were either released or placed in a large outdoor flight cage. Caged individuals were hand fed daily with different amounts of prey. The rate at which a male’s colors matured decreased both with decreasing food consumption and declining average air temperatures. A method is described for estimating the postemergence age of reproductively mature males from their color patterns upon arrival at a pond.