The development of Helicoverpa (= Heliothis) armigera (Hb.) (Lepidoptera: Noctuidae) on foliage, squares and bolls of four cotton cultivare [G 27, HD 167 (Gossypium arboreum), H 777 and H 974 (G. hirsutum)] and one hybrid (HHH 81) was studied under controlled conditions. The results indicated that some biological parameters were influenced only by plant parts and not by cultivar/hybrid. The larvae died as first instars when reared on the foliage of cv. G 27 and HD 167. Irrespective of cultivar, the larvae and pupae weighed more when the larvae were reared on cotton bolls than on squares and foliage. The larval and pupal periods were shortest for larvae reared on bolls, followed by squares and foliage. The fecundity of the female was highest when the insect was reared on bolls, followed by foliage and squares. The longevity of the female moth was highest in insects reared on bolls, followed by insects reared on squares, and on foliage. The longevity of the male moth was not influenced by rearing on the different plant parts. The duration of the life cycle was shortest for insects reared on bolls, followed by squares and foliage.