Bioenergetics of the Larger Grain Borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), Feeding on Corn

Abstract

An energy budget was developed for all life stages of Prostephanus truncatus (Horn) reared singly on whole corn kernels at 30 ± 0.05°C and 70 ± 2% RH. Materials removed from kernels, estimated consumption, respiration, insect biomass, and rejecta were determined. Mean energy in joules (J) accumulated in biomass per individual in the developmental stages was as follows: egg, 0.6; first instar, 1.2; second instar, 7.8; third instar, 37.9; prepupa, 40.4. The mean energy content of one corn kernel was 4,537 J. A mean of 547 J was removed by larval feeding, of which a mean of 252 J was estimated to be consumed. Adults consumed an estimate of 1,128–4,210 J during a life span of 45–168 d and could remove between 5,728 and 21,383 J. During development, 295 J were lost as frass and feces. The highest rate of O2 consumption (16.4 µl O2 · mg−1 · h−1) occurred in first instars 6 d old, but most oxygen was consumed by third instars at 16 d (28.2 µl O2 per individual per h), equivalent to an energy loss of 13.6 J · d−1. Cumulative respiration was 78.4 J for larval development and 85.1 j for adults at 26 d. Cumulative assimilation efficiency was 47.2%, gross production efficiency 16.0%, and net production efficiency 34.0%. The energy budgets of P. truncatus and nine stored-product pests were compared.