Erma S. Vanderzant

The role of ascorbic acid in the nutrition of three cotton insects

Abstract Purified diets were used to determine the effect of dietary ascorbic acid on the development of the boll weevil Anthonomus grandis (Boh.), the bollworm Heliothis zea (Boddie), and the salt-marsh caterpillar Estigmene acrea (Drury). It was shown that ascorbic acid is an indispensable nutrient for the growth and development of these three insects when reared under aseptic conditions. Boll weevil adults fed on diets deficient in ascorbic acid laid fewer eggs with lower hatch than adults that received this vitamin. Larvae from eggs of these adults that hatched did not survive beyond the second moult unless ascorbic acid was provided in the larval diet. When ascorbic acid was present in the adult diets, the eggs laid hatched into larvae some of which developed to adults even though their larval diets lacked the vitamin. Of the various stages of the boll weevil that were analysed, the egg contained the largest amount of ascorbic acid. Insects fed on ascorbic acid-deficient diets contained very little ascorbic acid. The bollworm and salt-marsh caterpillar have not been reared previously on purified diets. These two insects did not survive beyond the larval stage when their diets contained no ascorbic acid.

Nutrition of the adult boll weevil: Lipid requirements☆

Abstract Adult boll weevils ( Anthonomus grandis Boheman), reared from a defined diet, fed and oviposited similarly on defined adult diets with and without corn oil or fat-soluble vitamins. However, when both corn oil and fat-soluble vitamins were omitted from the adult diet, egg laying was markedly reduced. On adult diets lacking inositol, choline, or cholesterol, oviposition was less than half that obtained with the complete diet. Adults reared from larval diets without corn oil had a long pre-oviposition period and a high mortality. When fed the defined adult diet, they laid about half the number of eggs laid by females reared from a larval diet containing corn oil. Omission from the adult diet of corn oil and both corn oil and fat-soluble vitamins further reduced the number of eggs laid. Corn oil could be partially replaced by polyunsaturated fatty acids. The omission of most lipids and lipogenic factors did not seriously affect egg hatch. However, when adults were fed a diet deficient in cholesterol, not a single egg hatched after the eleventh day following their emergence.

Ascorbic Acid in the Nutrition of Plant-Feeding Insects

Bollworms, Heliothis zea (Boddie), and salt-marsh caterpillars, Estigmene acrea (Drury) gradually decreased in ascorbic acid content as they matured, even in its presence. Cotton leafworms, Alabama argillacea (H�bner), also lost ascorbic acid, although a dietary need for the vitamin was not proved. Pink bollworms, Pectinophora gossypiella (Saunders), reared without the vitamin, increased in ascorbic acid content as they matured, an indication that the vitamin was synthesized by the insect.

Nutrition of the adult boll weevil: Oviposition on defined diets and amino acid requirements☆

Abstract Boll weevil adults fed and oviposited on defined diets consisting of casein, amino acids, sugars, corn oil, cholesterol, inositol, choline, mineral salts, B-vitamins, agar, and water. No extractives of the cotton plant were needed to induce egg laying. Good oviposition also was obtained in protein-free diets in which amino acids and dextrin were substituted for casein. No eggs were obtained when arginine, histidine, isoleucine, leucine, lysine, threonine, tryptophan, valine, methionine, or phenylalanine were omitted one at a time from the diet. Eggs were laid by females fed diets containing the ten indispensable amino acids, glutamic acid, and glycine as the only sources of nitrogen for protein formation.

PHYSICAL ASPECTS OF ARTIFICIAL DIETS

The physical properties of artificial diets, texture, hardness, homogeneity, and water content are regulated by the addition of cellulose, agar, polysaccharide gums, and other large molecules. These physical aspects are important in promoting good growth and development of insects.