Danzig, E.M. 2004 [A review of species of the mealybug genus [Phenacoccus Ckll. (Homoptera, Coccinea, Pseudococcidae) associated with firs with a discussion of the polymorphism in Ph. piceae (Loew).]. Entomologicheskoe Obozrenye 83(3): 530-537.

Notes: A group of closely related species of the genus Phenacoccus living on different species of Picea is revised. This group consists from one Nearctic and five Palaearctic species. Phenacoccus piceae in contrast to other Palaearctic species is characterized by intraspecific variation in the number of circuli and presence of dorsal multiocular pores. Polymorphism of Ph. piceae is probably explained by its wide Euro-Siberian distribution and association with two different species of host plants, Picea abies in Europe and P. obovata in Siberia.