Scale insects are often overlooked because many do not look like typical bugs. While males resemble flies and have legs and wings, females become stationary on tree bark or branches and lose their legs and eyes by reabsorbing them. They grow a waxy covering that gives some species a protective shell. Some are shaped like tiny, headless turtles. Others may look like they are covered in white fluff or powder. These immobile females feed by tapping into the tree or host plant using a long needle-like mouthpart and sucking out plant juices. Some species of scale do not require males to reproduce, using parthenogenesis, a form of asexual reproduction, to create offspring instead.
Some species of scale are beneficial for chemicals that they produce that can be collected and used as dyes and wood finishing. Some feed on invasive plants, reducing their health and ability to spread. There are a variety of reasons why scale insects are considered undesirable, too. Their feeding habit can deplete a plant of vital resources on plant, weakening overall health. A few species of scale are tremendous crop pests. In addition, scale insects excrete a sweet, sticky substance called honeydew. The sweetness of it attracts ants. It also creates a perfect environment for a fungus to grow called sooty mold. This fungus is black and powdery, and notorious for coating stems and leaves, hindering photosynthesis, and causing affected areas to turn yellow. This makes the plant look sick and/or unattractive. The black sooty substance also falls onto pavement and cars beneath it.
Scale insects use all sorts of plants as hosts, and many species are plant specific, choosing to only live and reproduce on one type of plant. Trees, shrubs, ornamental house plants and flowering plants can all host scale. They are often seen on the underside of leaves and on tree branches. Dead ones remain on branches and their dried, waxy coating may easily come off when rubbed. Live ones are like little barnacles, clinging to the substrate. The best time to control scale populations is when they are still crawling and susceptible to treatments and removal, but pruning off branches and leaves after they have settled also helps reduce their numbers and impact. Natural controls include parasitic wasps and lady beetles.
Scientific Name: Various spp.
Colors: black; white; orange; green; yellow; red; brown
Note: An insect's reach is not limited by lines drawn on a map and therefore species may appear in areas, regions and/or states beyond those listed above as they are driven by environmental factors (such as climate change), available food supplies and mating patterns. Grayed-out selections indicate that the subject in question has not been reported in that particular territory. U.S. states and Canadian provinces / territories are clickable to their respective bug listings.