Abstract
Population processes and interactions among insects are mediated by thermally driven physiological time scales. The effects of temperature on developmental rates in Danaus plexippus and D. chrysippus were determined by rearing individuals under a range of constant temperatures. Rates of development changed in a linear fashion over a wide range of temperatures. The linear model accurately predicted development times under fluctuating temperatures for D. plexippus. The effect of this thermal time scale on competition between the 2 species is discussed.