Guanine accumulation in Boophilus annulatus (Say) at 15 temperatures (3-42 degrees C) showed embryonic development from 9 to 42 degrees C. Guanine concentrations steadily increased over the period of development. Eggs at 17-36 degrees C achieved hatch (requiring 54-12 d, respectively), and eclosion dates were estimated for larvae developing at 12 degrees C (day 172) and 14 degrees C (day 154) using linear regression. Development rates from 12 to 36 degrees C are described by a six-parameter biophysical model for poikilothermic organisms which defines three temperature development phases characterized by low-temperature (TL, 284.7 degrees K or 11.7 degrees C) and high-temperature (TH, 307.7 degrees K or 34.7 degrees C) enzyme inactivation and a linear region (RHO25, 0.049 day-1) of no temperature inhibition. A model of emergence distribution was derived by fitting a Weibull function to a single distribution representative of the normalized emergence distribution at each temperature.