Scale insects are small, immobile insects with no visible legs or antennae, pressed tightly against the plant on which they are feeding. Many are common and serious pests of trees, shrubs and indoor plants. Scale insects feed on plant sap. They have long, threadlike mouthparts (stylets) which are six to eight times longer than the insect itself. Scale feeding slowly reduces plant vigor; heavily infested plants grow poorly and may suffer dieback of twigs and branches. An infested host is occasionally so weakened that it dies. Scales often secrete a sticky honeydew which is attractive to wasps and ants and which supports the growth of black sooty molds.