The purpose of this article is to place before the fruit-growers and all interested in practial entomology, the main facts regarding the lifehistory, habits and appearance of the Oyster-shell Bark-louse Scale, and of the scales which are often mistaken for it. The damage done by this scale of late years has attracted so much attention, and so many enquiries have been received concerning the best methods for its eradication, that it is hoped earnest efforts will be made at once by all concerned to get it under control.