Tremblay, E., Tranfaglia, A., Rotundo, G., & Iaccarino, F.M. 1977 Comparative observations on some pseudococcid species (Homoptera Coccoidea).. Bollettino del Laboratorio di Entomologia Agraria 'Filippo Silvestri'. Portici 34: 113-135.

Notes: Planococcus citri, Pseudococcus calceolariae, P. obscurus and P. longispinus; evaluated degree of affinity through morphological and serological comparisons; similarity index.