Because the ingredients of the artificial larval diet (the basic diet) used to mass-rear the West Indian sweetpotato weevil Euscepes postfasciatus were expensive, so we substituted materials at 1/3 of the price (the low-cost diet). There was no difference in the survival rate of the weevil between those reared on the basic diet and those on the low-cost diet. As the quantity of artificial diet per rearing tray was increased, the survival rate of the weevil rose significantly up to 30 g of diet. The survival rate of the weevil was increased 1.6 fold by inoculating eggs in scratching lines 1 mm deep and 1 mm wide on the surface of the artificial larval diet. One hundred fifty eggs per rearing tray was probably a reasonable number because the survival rate and the actual number of surviving weevils at 150 eggs did not differ significantly from their respective maximums for other numbers of eggs. Rearing of 45,000 weevils per month was established using these methods. This represents a 4.5 fold increase compared to culturing by the conventional method. The new mass-rearing method could produce 1.6 adult weevils per gram of diet.