Schetters, C. 1960 Untersuchungen über die Art und die Folgewirkung des Saugvorganges bei der San José-Schildlaus (Aspidiotus perniciosus Comst.). [Investigations on the nature and effects of the sucking process in Quadraspidiotus perniciosus.]. Zeitschrift für Angewandte Entomologie 46(3): 277-322.

Notes: The salivary sheaths of the San José scale are variable in form and have numerous ramifications in the parenchyma tissue, especially at the ends, which can have several branches in fruits and non-woody parts of plants. As in many other plant sucking insects, the feeding stylets of the San José scale are surrounded in the plant tissues by a secreted sheath which acts as a guide. It must also contain enzymes which break down the cell sap on which the insect feeds. The necroses and other alterations seen in the lignified parts of plants are due to the action of these enzymes.