The Utilization of Starch by Larvae of the Flour Beetle, Tribolium castaneum

Abstract

The nutritional value of various starches, incorporated in marginal diets, for larval development of the flour beetle, Tribolium castaneum (Herbst), was assayed at 32°. Wheat, maize and rice starches were optimal. Larvae died when fed raw potato starch at 32°, but survived and developed slowly at 28°. Development was slightly better with boiled potato starch. The β-amylase limit dextrin “core” of potato starch — containing much esterified phosphorus — was devoid of nutritional value, in contrast with the high nutritional value of β-amylase limit dextrin of commercial amylopectin. The amylolysis of starch by Tribolium larvae is attributed mainly to the activity of α-amylase, the characteristics of which were examined. The in vitro hydrolysis of starches is loosely correlated with their nutritional value: amylopectin and β-amylase limit dextrin were well digested, but non-solubilized amylose, only slightly. Boiled potato starch was well digested, whereas raw potato starch was not. The similarity of these in vivo and in vitro results to those obtained with higher animals is noted, and the usefulness of this observation for the bioassay of starches is suggested.