Choice and no-choice tests for insect feeding were conducted following a previously described procedure . Wheat wafer discs (1 cm in diameter and 1 mm thick) were saturated by dipping them either in methanol only (control) or in a methanolic solution of the studied compounds (1%) to be tested. After evaporation of the solvent (30 min of air-drying), the wafers were weighed and offered to the insects in plastic boxes as the sole food source for 5 days. The feeding of insects was recorded under three sets of conditions: (1) on two control discs (CC), (2) on a choice between one treated disc (T) and one control disc (C; choice test), and (3) on two treated discs (TT; no-choice test). Each of the three experiments was repeated five times with 3 adult beetles (S. granarius), or 10 larvae (T. confusum or T. granarium). The number of insects depended on the intensity of their food consumption. The adults used for the experiments were unsexed and 7-10 days old. After 5 days, the discs were reweighed, and the average weight of eaten food was calculated as previously described .