Wade (1976, 1977b) reported an experimental study of interdemic selection for increased and decreased population productivity among laboratory populations of the flour beetle, Tribolium castaneum. In response to artificially imposed group selection, changes in adult productivity occurred rapidly, within three or four generations, and were large in magnitude, the between-treatment differences at times exceeding 100 adults per population. When this experiment was terminated after eight episodes of interdemic selection, the mean number of adults per population in the A treatment, selected for increased productivity, was 178 ? 8.2, whereas a mean of 20 ? .6 adults was observed in the B treatment, selected for decreased productivity. When these values are converted to per capita rates of population increase, the average A individual is found to produce 10.01 offspring per generation-more than 30 times the B average of .31 offspring per generation. The present study was conducted to investigate whether or not differences in productivity between the A and B groups would persist when interdemic selection was relaxed. In the viewpoint of some authors (cf. Williams, 1966; Emlen, 1973; Dawkins, 1976), individual selection within populations might be expected to lead to a rapid convergence of productivity in the A and B populations when selection between populations was relaxed. The expected rate of convergence by individual selection would be a function of the amount of additive genetic variance for traits affecting productivity that was present within populations at the end of the interdemic selection experiment. Although the amount of this genetic variance is unknown, its relative magnitude can be estimated from experimental studies of effective population size in Tribolium (Wade, 1980a, 1984).