Marotta, S., & Tranfaglia, A. 1995a Variability of morphological characters and its use in the systematics of mealybugs (Homoptera: Pseudococcidae).. Israel Journal of Entomology 29: 67-73.

Notes: Intraspecific variations in morphological characters are common in mealybugs; their incorrect or superficial interpretation has often led to proliferation of synonyms and neglect of studies on the possible existence of cryptic or sibling species; this paper reports a study of three species of Puto: P. superbus, P. tauricus and P. pilosellae; it is determined that use of morphological characters alone is not reliable enough for discrimination between P. superbus and P. tauricus and further biological studies are required; presence of a singular circulus was regarded as characteristic of P. pilosellae, however, a second circulus has been found in two specimens; discussion of use of occurrence and number of circuli as a fundamental taxonomic character.