Wikijunior:Bugs/Shield Bug

What does it look like?
There are over 200 known Shield Bug species. Size, body ornamentation and color vary greatly. Most Shield Bugs are green, gray, or brown to match their environment and are not easily noticed. Some species have bright colors.

They have a shield-shaped body. From the side, the back surface is slightly flattened and the underside appears slightly rounded. A distinctive, triangular shield hides the wings from the top and partially covers the abdomen underneath. A pale Y-shape often marks the back tip of the shield. The legs may be hairy or bristly and have only two segments at the end. The wings are well-developed.

Members of the Acanthosomatidae family are usually broadly oval or slightly tapering at the back end. On the small head are five-segmented antennae that may appear sunk into the front edge of the exoskeleton (pronotum). Antennae may have up to five segments.

Members of the Tessaratomidae family are often called Giant Shield Bugs. Some of these can be 1-1/2 inches long.

Shield Bugs are often referred to as stink bugs because they are similar in shape and emit a foul odor. Shield Bugs have only four odor-emitting glands on the abdomen instead of six.

Members of the Cydnidae family are called burrowing bugs. They are about ½ inch long and may be shiny brown, black, metallic, or bi-colored. They have a rounded, compact oval shape. Their spiny legs are adapted for burrowing into the ground.

Where does it live?
There are over 5000 Shield Bugs species worldwide. Several hundred species are found in warmer areas in the northern United States. They are abundant in wet meadows, especially on sedges. They can be found wherever there are woodlands and scrublands, but most live in subtropical and tropical regions.

Pentatomoidea, the largest Shield Bug family, is especially abundant in warmer regions of the southern hemisphere.

Many species of burrowing bugs spend part of their lives above ground hiding under stones and leaf litter.

What does it eat?
Most Shield Bug species are herbivorous (plant eaters), some are omnivorous, feeding on both plants and animals. They suck juices from shrubs, trees or other insects. The younger stages feed only on shoots or unripe seeds of a limited range of plants. The older immature stages and adults feed on a wide variety of plants.

Foliage of cypress trees is favored by some species. Elasmucha feeds on hanging spikes of small soft flowers of birch trees called catkins.

Burrowing bugs can burrow down three feet or more to suck root sap from plants.

Several species feed on other insects. Shield Bugs are sometimes called “timid predators” because they do not use their legs to overpower or manipulate prey. They attack slow-moving, defenseless creatures like caterpillars and aphids.

How does it defend itself?
Shield Bugs are well known for their ability to produce a foul odor secreted from the thoracic glands in adults and from the abdominal glands in nymphs. Some species are brightly colored to warn predators of the foul-smelling, bitter liquid. Other species have muted colors to blend into the environment.

Elasmucha grisea are known as “parent bugs” because of the care they give their young. They guard their eggs and newly hatched nymphs from the attacks of predators.

In Australia, an unpleasant species of the family Tessaratomidae can squirt a potentially blinding stream of defensive secretions.

What stages of metamorphosis does it go through?
Shield Bugs undergo simple metamorphosis, growing through three stages—egg, nymph and adult. The young or immature stages are called nymphs and often resemble small adults. The wings are less developed than those of the adult, and they are lighter in color.

The soft, pale nymphs are especially susceptible to predators. A new exoskeleton generally hardens in an hour or two. The nymph grows to its new size by taking in air. The wings are expanded by forcing blood into the veins.

What special behavior does it exhibit?
The female parent bug lays her eggs away from the catkin food source. She later leads the nymphs in a column to the food, like a mother duck leading her ducklings to water. She continues to care for her nymphs throughout their development.

Male and female burrowing bugs produce sound to attract a mate. They rub special pegs on the hind wings over file-like abdominal structures during courtship and mating.

How does this bug affect people?
The stink gland secretions are said to contaminate fruit when left on plants where Shield Bugs feed.

Giant Shield Bugs are reported to harm citrus crops.

The family Scutelleridae is reported to be a very serious pest of wheat and barley in West Asia. These Shield Bugs are referred to as “sunn pests” and damage crops by feeding on leaves, stems and grains. During feeding they are said to inject chemicals that harm the quality of flour made from these grains.