Insects resembling stink bugs often lead to confusion about their identity. Distinguishing between them is important for understanding their potential impact on gardens, crops, or homes.
Understanding the Stink Bug
The brown marmorated stink bug (BMSB), Halyomorpha halys, is recognizable by its distinctive shield shape and mottled brown and gray coloring. Adults typically measure about 14 to 17 mm long, roughly the size of a U.S. dime. It has alternating light and dark bands on its antennae and along the outer edge of its abdomen. When disturbed or crushed, this insect releases a characteristic pungent odor.
The BMSB is an invasive species, first reported in the United States in Pennsylvania in 2001, though it may have established earlier. It is a significant agricultural pest, feeding on over 100 plant species, including fruits, vegetables, and field crops. Feeding causes damage like pitting and scarring on fruit, making produce unmarketable. Adult BMSBs also seek shelter indoors in autumn to overwinter, becoming a nuisance pest.
Common Look-Alikes
Several insects are frequently mistaken for the brown marmorated stink bug due to shared physical characteristics. The Western conifer seed bug has a similar size and overall brownish color. Squash bugs also share a comparable coloration and are often confused with BMSBs.
Boxelder bugs, with their somewhat flat and oval shape, can also be mistaken for stink bugs. Leaf-footed bugs have a similar body structure. The rough stink bug, a species within the same family, is also commonly confused with the BMSB due to its similar size and brownish hue.
Key Distinctions for Accurate Identification
Differentiating the brown marmorated stink bug from its look-alikes involves observing specific visual cues.
Western Conifer Seed Bug
The Western conifer seed bug (Leptoglossus occidentalis) is typically about three-quarters of an inch long and reddish-brown, featuring a prominent white zigzag line across the center of its wings. It has flattened, leaf-like enlargements on its hind legs. While both produce an odor, its body is more elongated and narrower than the BMSB’s broad, shield-like form.
Squash Bugs
Squash bugs (Anasa tristis) are generally dark gray to dark brown and are typically longer and narrower than stink bugs, measuring about 5/8 inch long. They have an oval shape, less shield-like than the BMSB. Unlike the BMSB’s white wing overlap, squash bugs have a brown wing overlap and often a brown and white checkered pattern around their abdomen. Squash bug eggs are oval and copper-colored, laid in clusters on the underside of leaves, unlike the BMSB’s light green or yellow, barrel-shaped eggs.
Boxelder Bugs
Boxelder bugs (Boisea trivittata) are identified by their black bodies with distinct orange or red markings, including three red lines on the pronotum and fine red lines on each wing. They are approximately half an inch long and have a flat, oval shape. Unlike the BMSB’s mottled brown, boxelder bugs are clearly black and red, and their wings fold over their backs, creating an “X” pattern at rest. They lack the shield shape characteristic of stink bugs.
Leaf-Footed Bugs
Leaf-footed bugs are named for the leaf-like expansions on their hind legs, a feature absent on true stink bugs. These bugs often have narrow brown bodies with a yellow or white zigzag line across their flattened backs. Their antennae lack the distinct white banding of the brown marmorated stink bug.
Rough Stink Bug
The rough stink bug (Brochymena sulcata) closely resembles the brown marmorated stink bug in size and brownish color. It is distinguished by a rough or toothed edge on the front margin of its thorax (shoulders). It also has two white bands on its hind legs and no antennal bands, unlike the BMSB’s one hind leg band and distinct antennal bands.
Importance of Correct Identification
Accurate identification of insects is important for managing pest populations and safeguarding agricultural production. Even similar-looking insects have varied impacts and require distinct management strategies. Some are merely nuisance pests, while others cause significant crop damage.
Knowing if an insect is a serious agricultural pest, like the brown marmorated stink bug, or a less harmful nuisance, such as the boxelder bug, helps apply appropriate control methods. Misidentification can lead to unnecessary pesticide use or ineffective pest control efforts. It also provides peace of mind, helping individuals avoid undue alarm over harmless insects and focus on managing actual threats.