In this study were studied the biological characteristics of Spodoptera frugiperda and Spodoptera cosmioides larval in different food sources (sunflower leaves, soybean leaves, soybean pods, soybean leaves + pods and artificial diet). Under controlled conditions (25 ºC ±2 ºC, 70 ± 10% relative humidity and 12 h photophase) daily evaluated the larval weight and size, the duration and mortality of the larval and pupae stage and the weight of pupae. In general, both plant species (soybean and sunflower) can support S. frugiperda and S. eridania development, but the soybean was significantly less favorable of these species. These of lepidopterans, showed the faster developed, had higher survival and pupal weight in sunflower leaves and artificial diet, thus presenting the greater adaptability to food sources.
Key words: fall armyworm, Glycine max, Helianthus annus, nutritional ecology.