Larval competition in Drosophila melanogaster. I. Estimation of larval growth parameters.

Despite extensive research into the competitive interactions between the larvae of Drosophila for food, there have been few studies of the biological characteristics of the larvae which might underly competition. Here we present a sensitive method for estimating the larval feeding rate, larval gut capacity, larval conversion efficiency and larva-adult conversion efficiency, using radioactively labelled yeast. Two developmental stages, defined by the time since oviposition, were investigated in eight genetically distinct strains of Drosophila melanogaster. Significant genetic variation was recovered for all parameters at the second instar but only for conversion efficiency at the third instar. Feeding rate and the gut capacity had large and heterogenous error variances, especially in the third instar, while conversion efficiencies were relatively more stable.