Bioenergetics of Ephestia cautella (Walker) (Lepidoptera: Phycitidae) Feeding on Stored Wheat

Abstract

An energy budget of all life stages of Ephestia cautella (Walker) was developed for insects that fed on single wheat kernels at 30 ± 1°C and 80 ± 5% RH. Food consumption, respiration, and biomass of the insect's developmental stages, and energy content of insect by-products and feces were determined. Larvae consumed an average of 33.9 mg (605.5 J) of wheat during development. Lightest life stage was the egg at 0.006 mg, and heaviest stage was the adult female at 3.452 mg. Female pupae and adults were 18 and 10%, respectively, heavier than male counterparts. The mass of exuviae increased from 0.002 mg for first instars (L1) to 0.097 mg for L5. Energy content of immatures increased from 10.9 J/mg for eggs to 23.7 J/mg for L5. Average energy content for all larval stages was 19.3 J/mg; for adult males, 23.7 J/mg; and for adult females, 25.1 J/mg. Average energy content of exuviae was 21.7 J/mg and of webbing and feces, 9.5 J/mg. A wheat kernel contained 17.9 J/mg. Mean oxygen consumption decreased from 200 μl/mg per hour for L1 to 4 μl/mg per hour for pupae; oxygen consumption per individual increased from 1 μl/h for L1 to 30 μl/h for L5, and declined to 7 μl/h for pupae. Cumulative energy loss from respiration was 176 J in 35 days. Cumulative assimilation efficiency for E. cautella was 33.4% for males and 37.7% for females. Gross production efficiency was 10.8% for males and 14.3% for females and net production efficiency was 31.0% for males and 36.7% for females.