Growth and induction in food consumption of Helicoverpa armigera Hbn. (Lep., Noctuidae) larvae on chickpea, soybean, and maize diets

Laboratory studies were conducted to determine the effect of different artificial diets made of powdered seed materials of chickpea ( Cicer arietinum ), soybean ( Glycine max ), and maize ( Zea mays ) on the growth, consumption, and feeding preferences of Helicoverpa armigera larvae. Food consumption and growth of ultimate instar gram pod borer larvae were minimal on maize diet. The nutritive value of the soybean diet was higher, but the consumption rate of larvae was highest on chickpea diet compared with the other test diets. The growth of larvae was statistically equal on chickpea and soybean diets, in spite of differences in the consumption rate of these diets and their nutritive value. There appears to be a direct correlation between the quantity of the diets consumed and their nutritive value for growth of the larvae on chickpea and soybean diets. The lower nutritive value of chickpea diet is correlated with its higher intake by the larvae. Similarly, the lower consumption rate of larvae on soybean diet is correlated with its higher nutritive value. The diet on which the larvae were fed during earlier instars did not induce any feeding preference for that particular diet in the ultimate larval instar. The larvae consumed similar quantities of each of the three diets in their ultimate instar, irrespective of having fed on any of these diets during any preceding instars. However, induction in the quantitative consumption of food by the larvae was evident. The higher or lower consumption rate of diet by the larvae in the ultimate instar was influenced by their food during earlier instars. Hence the food consumption rate of larvae in the last instar appears to be set while feeding on a diet in the preceding instars.