Influence of Different Food Commodities on Life History, Feeding Efficiency, and Digestive Enzymatic Activity of Tribolium castaneum (Coleoptera: Tenebrionidae)

The life history, feeding indices, and digestive enzymatic activity of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) were studied on flours of 10 commodities (artificial diet, barley, cowpea, maize, millet, rice, sorghum, soybean, triticale, and wheat) at 30 +/- 1 degrees C, relative humidity 75 +/- 5% (12 h photophase). The maximum survival rate of immature stages was on artificial diet (75%), and the minimum rate was on soybean flour (30%). The duration of immature stages was significantly longer on soybean flour (33.3 +/- 0.6 days) than on other tested flours of commodities. Record for the highest fecundity of this insect was on artificial diet (418.9 +/- 9.1 eggs/female) and the lowest was on soybean flour (121.5 +/- 7.0 eggs/female). The results showed that fourth instar of T. castaneum reared on soybean flour had the lowest relative growth rate (RGR; 0.141 +/- 0.011 mg/mg/d) and efficiency of conversion of ingested food (34.59 +/- 0.009%). The amylolytic activity of fourth instar was the highest when larvae were fed on barley flour (8.97 +/- 0.25 mU/min/larva) and the lowest when they were fed on wheat flour (1.64 +/- 0.23 mU/min/larva). Larvae exhibited a single strong band of amylolytic activity among different flours of commodities; the lowest and highest intensity was for larvae fed on wheat and barley flours, respectively. The zymogram of the general protease activity showed four main bands, which the first band was unique for triticale-and artificial diet-fed larvae. The results of this study indicated that soybean flour was the most unsuitable food for feeding and development of T. castaneum.