Feeding and Nutrition of the Pea Aphid, Acyrthosiphon pisum (Homoptera: Aphidae), on Chemically Defined Diets of Various pH and Nutrient Levels1

Abstract

The pea aphid, Acyrthosiphon pisum (Harris), was maintained longer than 2 months and through almost 3 generations on an unnatural diet—a chemically denned aqueous solution of 40.17% dry matter consisting of 23 amino acids, 4.315%; 11 water-soluble vitamins, 0.146%; sucrose, 35%; mineral salts, 0.705%; and cholesterol benzoate, 0.0025%, at pH 7.6. During the first generation, growth on this diet for the first week or so was comparable to that on susceptible pea plants, though adults obtained on the diet weighed only half to two-thirds as much as those reared on the plants. Nevertheless, survival on both foods was similar. During the second generation growth was slower, some mortality occurred, and the adults obtained weighed half to two-thirds less than those on the plants. Variations in pH, or in the salt, sucrose, or total amino acid concentrations above or below those of the standard chemical diet usually resulted in reduced aphid growth, reproduction, and survival. Furthermore, aphids in preference tests could discriminate between different diets, and they usually selected and aggregated on those diets with a pH and a chemical composition closest to that of the standard diet. Finally, aphids on the diets remained apterous; they increased their original weights 12- to 30-fold, and they fed and excreted at rates 5–7 times less than those of aphids on pea plants.