The current work was carried out to investigate the effects of methanolic, petroleum ether and nbutanol extracts (30.0, 15.0, 7.5, 3.7 and 1.8%) of Nigella sativa seeds on several parameters of the adult performance and phase transition of Schistocerca gregaria. The n-butanol extract exhibited the most potent adulticidal activity followed with petroleum ether and methanolic extract, respectively, after treatment of penultimate (4th) instar nymphs. After treatment of last (5th) instar nymphs, methanolic extract exhibited the least adulticidal activity. Also, treatment of penultimate instar nymphs with N. sativa extracts resulted in blocked adult emergence in a dose-dependent course. Whereas no effect was exhibited by n-butanol extract on adult emergence after treatment of last instar nymphs, various degrees of restrained process was determined at some concentrations of other extracts. All N. sativa extracts (only at the higher two concentrations) caused adult deformities after treatment of the penultimate instar nymphs. After treatment of the last instar nymphs, nbutanol extract halted the adult morphogenesis only at the higher two concentrations but other extracts impaired it at all concentrations. In connection with the phase transition, treatment of penultimate instar nymphs with n-butanol extract (at 15.0 %) resulted in a solitarious tendency of S. gregaria adults as appeared with deeply green colour. The ovarian maturation in adult females was pronouncedly or slightly prohibited by N. sativa extracts during prolonged duration, depending on the concentration. Also, the reproductive life-time (oviposition period) was affected. Total adult longevity was shortened or prolonged, i.e. adult aging was accelerated or delayed, depending on extracts, concentration level and time of treatment.