| Summary: | On the market since 1996, genetically modified plants expressing an insecticidal toxin (Cry toxin stemmed from <em>Bacillus thuringiensis</em>) target several lepidopteran and coleopteran pests. In this study, we assessed the impact of two varieties of <em>Bt </em>maize producing different toxins (Cry1Ab or Cry1Fa, respectively) on the biology of a storage pest: <em>Plodia interpunctella </em>(Hübner) (Lepidoptera: Pyralidae). The Indianmeal moths were susceptible to both toxins but showed an escape behavior only from Cry1Fa. The weight of females issued from larvae reared on Cry1Ab increased with increasing toxin concentration, but adults of both sexes reared on Cry1Fa had decreased weight. Both toxins increased development time from egg to adult regardless of sex and had no impact on the male adult lifespan. Finally, we recorded a time lag between metamorphosis from the non-<em>Bt </em>and the <em>Bt </em>diets, which increased proportionally to Cry concentration in the <em>Bt </em>diet.
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