Neuffer, G. 1964 Bemerkungen zur Parasitenfauna von Quadraspitiotus perniciosus Comst. and zur Zucht bisexueller Prospaltella perniciosi Tow. im Insektarium.. Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz 71(1): 1-11.

Notes: Title in English: [Remarks on the parasite fauna of Quadraspitiotus perniciosus Comst. and on the breed of bisexual Prospaltella perniciosi Tow. in the Insectarium]. In mass culture the bisexual San Jose scale parasite Prospaltella perniciosi soon becomes unisexual (parthenogenetic). There is no evidence that bisexual P. perniciosi, which became unisexual in the insectary, regains bisexuality after liberation in the field. This experiment attempts to maintain its bisexuality through the use of imported apple twigs infested with San Jose scale from Conecticut and Wisconsin to Stuttgart, and by a technique of alternating temperatures.