Leaf weight and leaf area of peanuts,Arachis hypogaeaL. cv. ‘Florunner,’ consumed by three size classes of the fall armyworm,Spodopterda frugiperda(J. E. Smith), were determined under controlled conditions. Measurements were taken for peanut chronological ages of 45–70 (class 1), 67–92 (class2), and 92–120 (class3) days post-planting, respectively. Results indicated feeding rates for large larvae increased from 0.18 to 0.35g/larva/day as plant foliage progressed from class 1 to class 2. Oviposition increased from a mean of 486.5 to 1111.5 eggs/moth as larvae were fed class 2 foliage versus foliage in class 1. Mean adult female longevity 13.3 days) for adults whose larvae fed on class 3 foliage was significantly greater than longevities of moths from foliage classes 1 or 2.