Confused flour beetle, Tribolium confusum is a major pest of grains and grain products. Some legumes hitherto not used as major food are gaining interest due to increase in human population and the need of food and feeds. Susceptibility of fresh and processed Glycine max and Cajanus cajan flours, and white wheat flour (control) to T. confusum was studied towards planning effective storage techniques, and developing cheap insect diet. Ten copulating pairs of the beetle were introduced into 20 g of each flour. Number of eggs laid, emerged larvae, pupae, eclosed adults, and duration of development of each insect stage was used as indices of survival of T. confusum on the flours. Proximate composition, saponin; and α-amylase and protease inhibitors contents was used to determined suitability of each flour as insect diet. Highest (201.00) and lowest (62.40) numbers of eggs were recorded in wheat and fresh soybean flours. Highest percentage of emerged larvae (92.76), moisture (10.40) carbohydrate (63.96) and α-amylase inhibitor activity (45.10mg/ml/min) were found in wheat. However, fresh Soybean flour had the highest crude protein (39.83%) while wheat had the lowest (20.52%). There were no significant (p > 0.05) relationship between number of egg and anti-nutrient (r2 = 0.91), and proximate composition of the flours (r2 = 1.00). Mantel-Cox Log rank index revealed survival time significantly increased from fresh flour to roasted ones for larvae (Z = 76.17; p < 0.0001), pupa (Z = 63.18; p < 0.0001) and adult (Z = 21.16; p < 0.0001). The study reveals better survival of T. confusum on the processed legume flours due to reduced anti-nutrients and suitability of the flours as insect diet.
Keywords: T. confusum, Glycine max, Cajanus cajan, Survival, Insect diet