Bioenergetics of granivorous beetles, Cryptolestes ferrugineus and Rhyzopertha dominica (Coleoptera: Cucujidae and Bostrichidae)

Abstract

The weights and caloric values of insects and exuviae, the food consumed and egested, and oxygen respired were estimated at regular intervals for all stages of the rusty grain beetle, Cryptolestes ferrugineus, reared on wheat kernels. Immature stages assimilated between 66 and 79% of the food consumed and the proportion of assimilated energy converted into tissue growth increased from 3 to 23% during development. Similar observations were made for the lesser grain borer, Rhyzopertha dominica, but the food consumed and egested was not measured because much of the kernel chewed by this insect was not ingested, leaving a frass of white powder difficult to separate from the rejecta. For R. dominica a maximum of 38% of the energy assimilated during development was converted into tissue. Adults of both species used most energy to produce eggs. The net efficiencies of the use of energy for reproduction are higher in some stored-product beetles whose populations increase more rapidly than those which increase more slowly.