The whitefly genus Rhachisphora Quaintance & Baker is reported for the first time from the Andaman Islands. Puparia and earlier stages of immatures of a new whitefly, R. saddlensis sp. nov. found infesting Semecarpus kurzii Engl. (Anacardiaceae) are described with illustrations of its habitus on the leaf, line drawings, photographs, and SEM microphotographs of the type specimens are provided. Puparia of the new species differ from other Rhachisphora species in having an elongate cordate vasiform orifice, a row of submarginal pores and the caudal tracheal pore deeply inset from the margin. The new whitefly is dimorphic in which female puparia are larger than the male puparia and found feeding on both surfaces of the leaves. In addition, an identification key to Rhachisphora species known from India is provided.