Food consumption and utilization by Tribolium confusum du Val (Coleoptera: Tenebrionidae) larvae and their susceptibility to the acetone extract of Nerium oleander L. (Apocynaceae) leaves in relation to three types of flour

Abstract

The nutritional indices of Tribolium confusum larvae reared on wheat, barley and corn flour and their susceptibility to acetone extracts of Nerium oleander leaves were studied. In addition, the concentrations of total protein, carbohydrate and lipid in the flours and the larvae reared on them were also determined. Although the lowest consumption index and relative growth rate (RGR) were obtained in larvae reared on corn flour, these showed the highest weight gain. No significant difference was apparent between the three types of flour in terms of digestibility, or between the RGR of larvae reared on barley and corn flour. In contrast, the RGR of larvae reared on wheat flour was significantly higher than that for those reared on barley and corn flour. The highest food utilization, in terms of the efficiency of conversion of ingested and digested food into biomass, was reached in larvae reared on corn flour. Larvae reared on wheat and corn flour had the highest and lowest total protein contents, respectively, while larvae reared on corn and barley flour had the highest and lowest total lipid contents, respectively. On the other hand, no relationship was evident between larval and flour total carbohydrate content. The present study showed that larvae reared on corn flour were more tolerant to acetone extracts of N. oleander leaves than those reared on wheat or barley flour. The relationship between the total protein, carbohydrate and lipid contents in the flour and the larval nutritional indices, and also the susceptibility of larvae to the botanical extract, were discussed.