Polyacrylamide gel electrophoresis (PAGE) was used to detect non-specific esterases (EST) in the adult and pupae of three species of whiteflies, Bemisia tabaci (Gennadius), B. tuberculata (Quaintance and Baker), and Tetraleurodes acaciae (Quaintance). Esterase banding patterns of over 216 adults from 22 collections in Jamaica matched the B type esterase banding pattern of the B biotype from Arizona. Eighty-six per cent of the plant species sampled in Jamaica were hosts of the B biotype of B. tabaci. These host plants included members of the Malvaceae, Euphorbiaceae, Solanaceae, Cucurbitaceae, Cruciferae, Caricaeae, Amaranthaceae, Papaveraceae, Caesalpiniaceae, and the Compositae family. Bemisia tuberculata and T. acaciae were monophagous colonizing Bocconia frutescens and Capsicum annuum, respectively. The esterase banding patterns of the three whitefly species studied were found to be electrophoretically distinct from each other. This study demonstrates that the pattern of esterase isoenzyme is species specific and may be used to identify and differentiate between whitefly adults, which are often difficult or impossible to identify morphologically.