Spruce beetles (D. rufipennis) from a population homogeneous with respect to population quality were subjected to different degrees of competition at corresponding stages of their reproductive cycles by varying the spacing of individuals and by varying the time of introduction of individuals into the competitive environment. Competition effects increase with gallery accumulation, as suggested in previous studies, and result in subsequent reduction of gallery production and oviposition. Increase in individual beetle quality, however, confers increased powers of resistance to the competition effects. Initial egg-free length is an unsuitable attribute for comparisons of populations. Expression of reproductive efficiency is a dynamic population characteristic which varies over the reproductive cycle, and which may be readily estimated by measurement of yolk deposition rate. For comparing populations, such measurements would be more valuable when carried out before the onset of competition effects. Individuals with the highest quality at the start of the egg-production cycle exhibit the highest reproductive efficiency as conditions change.