Stink bugs are often referred to as shield bugs because they have a triangular plate on their backs which very much resembles a shield. They get their derogatory name from the foul-smelling liquid they emit from glands located on the underside of their thorax and which they release from pores on the sides of their bodies. The production of this stench is a defensive mechanism which the bugs employ when they are provoked by predators or mishandled in some way.
Shield or stink bugs belong to the hermiptera order, which is comprised of between 50,000 to 80,000 species of true bugs such as cicadas, planthoppers, leafhoppers, aphids, and bedbugs. Their colouration normally ranges from brown to green, although there are some varieties that are very striking in appearance, bearing bright yellow, brilliant green, red, purple, and black dots or bands in their shields.
Like other members of the hermiptera order, the majority of stink bugs are herbivores and feed on plants. They have sharp needle-like mouth parts that they use to pierce the plants they’re feeding on and suck out their juices. Preferring fruits such as apples, melons, peaches, and tomatoes, shield bugs have also been known to feed on vegetables such as beans and crop plants such as cotton. Their colours enable them to blend in effortlessly with their natural surroundings – i.e. gardens, orchards, and farms. Because they reproduce rapidly, stink bugs have the potential of becoming agricultural pests. Many times, though, stink bugs feed only on one host plant and leave the surrounding plants alone. When they feed on a plant, their effect is to cause cosmetic damage, making the plant or fruit difficult to sell. There are some species of shield bugs, however, that are predatory; they feed on caterpillars and other pest insects. These ones are considered beneficial to have around in farms and orchards as they serve to prevent other pest insects from destroying crops and plants.
Different species of stink bugs exist in most parts of the world. In the United States, they used to be prevalent mainly in the southern states, but recently a species imported from Asia has been seen particularly in the Middle Atlantic States such as New Jersey and Pennsylvania.
In most areas, shield bugs are active from spring to late fall. During the warm months, the females produce hundreds of eggs and deposit these underneath plant leaves and stems. In warmer areas, they can do this twice yearly. Because they produce so copiously, their presence can potentially grow quickly into plague proportions. However, normally the stink bugs’ natural predators keep their numbers in check. Once the eggs hatch, they go through five stages before they reach their full-sized adult stage. In their immature nymph stage, they are smaller and wingless, although they already possess the scent glands they are so maligned for. They also possess the piercing and sucking mouth parts that their grown-up versions have. Adult stink bugs, on average, grow to ¾ of an inch.
Stink bugs dislike the cold, and before cold weather begins, they begin their search for warmer climes. In this manner, they become real pests to homeowners as they look for ways to enter houses and hibernate there for the duration of the cold season. Although they are harmless to humans, their presence is often a nuisance to many, especially when they congregate in swarms. Improper methods of disposing of the insects often cause a stench that many find difficult to abide.