Glanded and glandless cotyledonary cotton leaves, were used to compare the effects of glandular chemicals (primarily gossypol) on the survival and development ofAlabama argillacea(Hübner), a specialist on Gossypieae, andHeliothis virescens(F.), a polyphagous species.A. argillaceasurvived equally well on either leaf type and the weight of late-larval instars was significantly increased by feeding in glanded leaves. However, survival and pupal weight ofH. virescenswere reduced by this food. The differences in response to glandular chemicals by these two species suggest that changes made in plant chemistry to enhance the resistance of plants against generalist feeders may not lessen, and may in fact increase, the impact of adapted specialists on cotton.