[1] The main species of tree which act as hosts for this scale insect are horse chestnut, sycamore, maple, lime, elm, magnolia, bay and dogwood.

This is thought to be due to various habitat differences in urban settings; higher temperatures, more air pollution, lower availability of nutrients, and more stress caused by lack of moisture (more run-off and less water penetrating the ground).

[3] P. regalis is primarily a pest of urban trees; its sap-sucking activities reduce its hosts' vigour, and the excess honeydew produced by the insects encourages the growth of sooty mould, which is unsightly.

[1] The adult scale insect resembles a limpet and remains stationary on the bark of its host tree where it feeds on sap.

[4] In early summer, the mature female lays white, circular egg masses which become visible as they protrude slightly from under her brown scale.