Population parameters (mean generation time, intrinsic and finite rates of increase, and days for population to double) and the components of the intrinsic rate of increase (developmental and prereproductive times, total fecundity, percent immature mortality, and fecundity rate) were estimated forMonelliopsis pecanis,Monellia caryella,Melanocallis caryaefoliaein clip cages placed on pecan,Carya illioensis(Wang.) K. Koch, leaflets exposed to ambient environmental conditions in an orchard from mid-June to late October. Developmental and prereproductive times differed between species and decreased over time during the growing season. Females produced less progeny when their offspring remained in cluster in the cages for 4–6 d than when offspring were removed daily after counting. Mortality was not a factor in determining the rate of increase because of low mortality of nymphs during the reproductive periods.M. caryellahad the shortest developmental, prereproductive, and generation times and required less time for its population to double, yetM. caryellahad the highest mean total fecundity, fecundity rate, and intrinsic and finite rates of increase. Results are compared with studies from the literature done at constant temperatures.