A study was conducted to determine preimaginal developmental rate, adult survival, and fertility of two populations ofEretmocerussp. that parasitizeBemisia tabaci(Gennadius). An arrhenotokous parasitoid population was collected in Indio, Calif., and a thelytokous parasitoid population was collected from Oahu, Hawaii. Experiments were conducted with parasitoids reared onB. tabacihosts living on cotton,Gossypium hirsutumL. (‘Delta Pine 61’), or cucumber,Cucumis sativusL. (‘Poinsett 76’), in temperature-controlled cabinets at 20.0 and 29.0%C. Significant differences in preimaginal developmental periods were found between populations, temperatures, and plants. Adult longevity was greatest at lower temperatures. A limited preoviposition period existed. Fertilities were higher on cucumber and at 29.0%C. The sex ratio of the arrhenotokous population favored females. The intrinsic rate of natural increase (rm) for the arrhenotokous population varied from 0.0610 to 0.1149 on cotton and from 0.0856 to 0.1824 on cucumber, at 20.0 and 29.0‘C. Values for rmfor the thelytokous population varied hom 0.0858 to 0.1608 on cotton and from 0.0980 to 0.2117 on cucumber, at 20.0 and 29.0%C. The results indicate that biological control ofB. tabaciwould probably be better obtained byEretmocerussp. population from Hawaii at higher temperatures.