Female moths of the tobacco budworm,Heliothis virescens (F.), oviposit in the terminals of the cotton plant,Gossypium hirsutum (L.). The hatched larvae migrate to the terminal area and then to small squares (buds), on which they feed, finally burrowing into the anthers where they grow and develop. They attempt to avoid gossypol glands as they feed. Chemically related evidence explains, in part, these observations. The calyx crown of resistant lines (which is avoided) is high in the terpenoid aldehydes (TAs) including gossypol. HPLC data showed that the gossypol content of both susceptible and resistant glanded lines is equal, while the hemigossypolone and heliocides H1 and H2 are greatly increased in resistant lines and presumably are more closely associated with resistance. Analysis for total amino acids in cotton square tissues showed that there was a gradation from the calyx and calyx crown, which were lowest, to the anthers, the site of final insect development, which were highest. Synthetic diets mimicking amino acid distribution in anthers were found to be successful for larval growth and development.