Scale insects are attacked by many beneficial parasitic and predatory insects, which keep them in check in many areas. They are divided into armored scales, soft scales and mealy bugs. Armored scales are protected by a stiff waxy covering which they secrete and enlarge as they grow, but it is free from their body. After a female scale has settled it does not move. Soft scales have a cottony or feltlike deposit on the backs but no free covering.
Some species move slightly in the young stages.
The best known soft scales are terrapin scale, European fruit lecanium, cottony maple scale on citrus and the soft brown scale on many plants in the South and in greenhouses. Mealybugs move about freely for most of their life but often live in colonies. Their bodies are covered with long waxy threads. Citrus mealybug, long tailed mealybug, coconut mealybug, pineapple mealybug and cottony cushion scale are destructive pests in the warmer areas. Greenhouse orthezia and many of the above species infest greenhouse-grown plants and the taxus mealybug is destructive in cooler areas.