Morphology of the third antennal segment and compound eyes of adults of the whitefly species Bemisia tabaci (Gennadius), B. argentifolii Bellows & Perring, B. tuberculata (Bondar), Trialeurodes vaporariorum (Westwood), T. variablilis (Quaintance), and Aleurotrachelus socialis (Bondar) were studied using scanning electron microscopy to aid in identification of adult whiteflies in cassava and beans in Colombia. Random amplified polymorphic DNA polymerase chain reaction markers proved complementary to the morphological identification of whitefly species and the only rapid method to distinguish individuals in the Bemisia tabaci species complex. From each species of whitefly, a region of the mitochondrial 16S rDNA gene was amplified, cloned and the sequence determined. Parsimony and distance analyses were performed and the results were similar to those based on morphology. The distance between the two species of Trialeurodes was greater than expected for two species within the same genus. The combination of morphological and molecular traits is useful in understanding the diversity and evolution of these whitefly species.