Bioenergetics of the granary weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae)

Abstract

Cumulative energy budgets were determined for the immature and adult stages of Sitophilus granarius (L.) reared on single wheat kernels, Triticum aestivum L. Caloric values (cal/mg dry weight) for S. granarius stages reared at 30 °C and 70% relative humidity (RH) were 5.792 for eggs, 5.989 for third-instar larvae, 6.474 for prepupae, 5.985 for pupae, and 5.975 for adults. Larval production increased exponentially from 0.13 cal in early first-instar larvae to 12.0 cal for 20-day-old fourth-instar larvae and prepupae, and declined to 6.9 cal during the pupal stage.To complete development larvae consumed a mean 62.6% of a 126-cal kernel, whereas an average adult consumed over 3.5 times more than the total larval consumption. Assimilation efficiencies for larval development were similar (73.9 to 76.2%) at three temperatures, 20, 25, and 30 °C. Of energy consumed during larval and pupal development, 65.7% was explained by respiration. Net production efficiency was 20% for all larval stages and 48% for total egg production by an adult.