The developmental responses ofSpodoptera eridania(Cramer)Pieris rapae(L.). fed onBrassica nigra(Koch) plants grown with four nutrient solutions were studied. When assayed, the plants from the different nutrient treatments (basic nutrient solution, low nitrogen, low sulfur, and 10% of basic nutrient solution) had dissimilar chemical profiles with respect to allylisothiocyanate concentration, protein concentration, and water content.S. eridaniagrew fastest on the low-sulfur plants and did not complete development on plants grown with the low-nitrogen or low-basic-nutrient solutions.P. rapaedeveloped most rapidly on the low-sulfur and low-nitrogen plants. The reasons for these developmental responses are discussed.