Scales are most commonly of a brown or whitish color, flat or tortoise-shaped, and easily seen. They adhere closely by the under surface of their bodies to the stems, branches, and foliage of woody plants. The mature Insect is stationary, and its body at length becomes a shell containing hundreds of eggs. These hatch, and the young emerge from the shell, crawl about and settle, to develop into the familiar form. A strong solution of fir-tree oil, like that used for mealy bugs, is a good remedy. A strong solution of whale-oil soap, made by adding an ounce or more of the soap to three gallons of water, even more if necessary, is also useful in combating them. After dipping or syringing the plants they may be allowed to stand over night, when they should be rinsed off with clear water. Applications may need repeating every three or four days until the Insects are gotten rid of. It is difficult, for a time, to tell when they are dead. If killed, the bodies will fall off easily, and in the case of the soft-shelled species shrivel up somewhat after a time. Kerosene and water emulsion (see _Kerosene_) will kill them.
INSECTICIDE. A substance which will kill insects. Insecticides are of two general classes--those that kill by contact (see _Kerosene_), and those that poison the insect (see _Paris Green_ and _Hellebore_).
IRIS. Many handsome perennials, of which the Blue Flag is familiar to every old-fashioned garden. Most Irises thrive best in a rather moist soil, and some of them may be colonized in the water in margins of ponds. Gardeners usually divide them into two sections--the tuberous-rooted or rhizomatous, and the bulbous. A third division--the fibrous-rooted--is sometimes made. The common and most serviceable species belong to the tuberous-rooted section. Here belongs the beautiful and varied Japanese Iris, _Iris lævigata_ (or _I. Kæmpferi_), which is among the most deserving of all hardy perennials. Most of these Irises need no special care. They are propagated by division of the rootstocks. Plant the pieces 1 foot apart if a mass effect is desired. When the plants begin to fail, dig them up, divide the roots, discard the old parts and grow a new stock, as before. _I. Susiana_, of this section, is one of the oddest of Irises, but it is not quite hardy in the North. Of the bulbous section, most species are not hardy in the North. The bulbs should be taken up and replanted every two or three years. The Persian and Spanish Irises belong here. The bulbs give rise to but a single stem.