Population growth of lesser grain borer, Rhyzpertha dominica (F.), in 135-kg lots of hard red winter wheat, Triticum aestivum L., was monitored at 3 grain moisture levels (≈10, 12, and 14%) at each of 3 temperatures (≈22, 27, and 32°C). Over this range of environmental conditions, a published population growth model explained 64–96% of the variation in insect density. Based on published studies and new data collected for developmental times, new equations were developed for egg production and developmental time, and daily adult mortality was estimated. Substituting new equations and mortality rate in the published model improved predictions, increasing by 3–24% the percentage of variation explained. The biggest improvements tended to be at the extreme grain moisture and temperature conditions.