Colonies of Indianmeal moth, Plodia interpunctella (Hübner), and almond moth, Cadra cautella (Walker), reared in the laboratory on diet treated with Bacillus thuringiensis, became resistant to B. thuringiensis. However, resistance did not progress at the same rate or to the same extent in all of the colonies. Resistance in five Indianmeal moth colonies increased from 2- to 29-fold within three generations, and from 15- to 100-fold in ca. 40 generations under relatively low selection pressure. With higher selection pressure, resistance in one colony increased >250-fold. Resistance in an almond moth colony increased only ca. 7-fold in 21 generations of intensive selection. Resistance was stable when selection was discontinued after the resistance levels reached a plateau, but declined if selection was discontinued earlier. The resistance was partially recessive in the five Indianmeal moth colonies, but not to an equal extent. The resistance assorted independently of the recessive genetic markers copper, golden, and white-eye.
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McGaughey et al. (1988) studied this question.