Significant spatial or temporal variability (or both) is shown in the physiological time (degree-days) needed for males of the tufted apple bud moth,Platynota idaeusalis(Walker), redbanded leafroller,Argyrotaenia velutinana(Walker), codling moth,Cydia pomonella(L.), and spotted tentiform leafminer,Phyllonorycter blancardella(F.) to complete one generation. For the four insect species at all geographic locations (North Carolina, West Virginia, Pennsylvania, and Michigan), the degree-day requirement for a generation is significantly smaller if the requirement is measured between the beginning of flight periods rather than between flight peaks. The degree-day requirement per seasonal generation significantly increases from spring to autumn for redbanded leafroller and spotted tentiform leafminer. Latitudinal effects on generation time for the tufted apple bud moth and redbanded leafroller show that the insects develop significantly faster and exhibit more synchronized flight periods with increasing latitude. Similar elevational effects are shown for tufted apple bud moth. Laboratory data do not give developmental parameter estimates that yield accurate phenology model predictions for three of the four species, and tufted apple bud moth developmental data from field cage rearings likewise give inaccurate parameter estimates for phenology model predictions. Model predictions of seasonal male flights are most accurate if model developmental parameters are estimated from monitoring field populations and these parameters are specific both spatially and temporally.