Abstract
A comparison between Encarsia formosa GAHAN and Encarsia transvena (TIMBERLAKE), the parasitoids of the tobacco whitefly Bemisia tabaci (GENNADIUS), was made by conducting laboratory experiments on host instar choice and functional response to host density. E. formosa preferred young instar B. tabaci larvae such as the second instar ones and old instar larvae such as the fourth instar for host feeding. E. transvena preferred fourth instars both for host feeding and oviposition. When fourth instars were used, the functional response of the parasitoids followed a saturation type curve in which E. formosa was superior to E. transvena both in host feeding and oviposition.
