Self-Selection of an Optimal Nutrient Mix from Defined Diets by Larvae of the Corn Earworm, Heliothis zea (Boddie)

Abstract

Last instar larvae of the corn earworm, Heliothis zea (Boddie), self-select an 80:20 protein:carbohydrate (casein:sucrose) ratio when offered two diets that are identical and complete except that one lacks casein and the other lacks sucrose. This ratio is nutritionally superior to four others, ranging from 100% casein to 100% sucrose, when incorporated in otherwise equivalent diets and fed to larvae throughout the last instar. The 80:20 ratio supports the best overall utilization of food (ECI) and the highest conversion of digested food to biomass (ECD). When the 80:20 ratio is fed throughout larval development, it is found to be better than the 50:50 ratio (the next best) with respect to growth rate and mortality. It is proposed that in nature most insects have both the opportunity and the capability to self-select a favorable nutrient mix. Herbivorous insects, for example, could self-select from an array of different plant species or from the various structures and tissues of a plant.