Aspects of the development and mortality ofIps avulsus(Eichhoff) were studied at seven constant temperatures from 10 to 35°C. On average, eggs occupied 10.3% of the total time in the host, larvae 34.8%, pupae 11.8%, and teneral adults 43.1%. Plots of development rates (reciprocal of median times) and percent mortalities versus constant temperatures indicated that the insect is well adapted to high temperatures but sensitive to low temperatures. The timing of oviposition relative to sibling oviposition time in a slab had little effect on the development times of any life stage or the life cycle. Oviposition time influenced life-stage and life-cycle mortality, although the effects were not great. For example, the probability of larval death increased from 16.6 to 28.7% for individuals originating in the first and fourth quarters of the oviposition period. The probability of death due to cannibalism was less than 10% and was not influenced by oviposition time. No difference was observed in the overall proportion of males to total emerging beetles (0.496) and 0.5; however, this proportion increased with time throughout the emergence period. Models were developed to predict life-stage and life-cycle development times as functions of temperature. A mechanistic model described the development rate versus constant temperature relationship, whereas a cumulative Weibull function described the temperature-independent distributions of normalized development times. The life-cycle model was validated using a multiple-cohort simulation procedure and data ofI. avulsusemergence from three trees in each of three field plots. The validation indicated model suitability in a larger model of population dynamics, although additional testing is indicated.