Bonsai tree

Scale are another ubiquitous garden variety pest in temperate regions. Scales are some small insects of the order Hemiptera, generally classified as the superfamily Cocoidea. There are about 8000 species of scales, with many of that rather large number considered pests on our plants. Scales are one of the most destructive insects in the United States, with many species invaders from other areas of the world. They can survive in harsh condittions, from the tundra to the tropics and thrive on all parts of a plant, commonly the underside of the leaves and on branches. They are not limited in their location region.

There are three general categories scale insects fall in to: Diaspididae or armored scales; Cocidae or soft scales; Pseudococidae, commonly known as mealybugs. The armored scales are the ones with the most effective outer coating, and subsequently, the most dificult to deal with.

Scale Habits: Most of the scales are plant parasites. They feed on the sap of a plant, usually puled directly from the vascular system. While one or two scale may not be a cause for alarm, a host of these little criters feeding on a tree will quickly lead to problems. Some scales feed exclusively on one type of plant. Others target a small number of species.

Soft scales and mealy bugs can excrete honeydew, sometimes in large amounts. Sooty mould happily grows on this stuff and while it is generally harmless. Ants are also attracted to the honeydew excreted, though they do not herd scale the same way they do aphids. Armored scale do not excrete honeydew.
Scale Reproduction/Life cycle: The sexual differences in appearance between male and female are huge in scale insects. Mature female scale are sessile, have no legs or antenae, usually much larger than the males and are usually the ones we see when we notice a scale infestation. Mature males are smaller, typically have visible wings and they do not feed and die in a day or two.

Anatomy of a Scale Insect: Scale insects vary greatly in size, as well as appearance. They can be very tiny, at only a millimeter in diameter, or a little larger, though few are larger than about five milimeters across. Scale come in almost any colour, from brown to green, white to yellow, all depending on the species. The appearance of the armor can vary not only with species, but also the host plant the scale is feeding on, gender, life cycle stage, time of year and other environment conditions, which can make identifying the particular species, or even genus, of scales by the layman, very difficult.

All scales have antenae and six legs, though mature females lose these features completelly. They have piercing and sucking mouth parts.