Stink bugs are common insects found in homes and gardens. Identifying them accurately helps in understanding their behavior, especially since some are considered pests while others are beneficial.
Overall Appearance
Stink bugs are recognized by their broad, flattened bodies, which often resemble a shield when viewed from above. This body shape earns them the nickname “shield bugs” in some regions. Adult stink bugs typically measure around 0.5 to 0.75 inches (1.27 to 1.9 cm) in length, and are nearly as wide as they are long.
Their coloration varies, though many commonly encountered species are mottled brown, gray, or green. This range of colors provides camouflage, allowing them to blend into their natural surroundings like bark and foliage. The underside of many stink bugs, such as the brown marmorated stink bug, is often a creamy white-brown or light gray.
Specific Body Features
Their head often appears somewhat triangular and is typically tucked into the front margin of the pronotum, which is the shield-like segment behind the head. They have two antennae, each composed of five segments, which they use to explore their environment. Many species display distinct banding on their antennae, which can be a key identifying mark.
They have six legs, which are relatively slender and adapted for crawling and gripping surfaces. A prominent triangular plate, known as the scutellum, is located in the center of their back, covering a significant portion of their abdomen. This scutellum can be the same color as the rest of their body and in some species, it covers nearly their entire back.
Adult stink bugs have two pairs of wings, with the forewings, called hemelytra, having a hardened base and membranous tips. When at rest, these wings fold over their back, with the membranous tips often overlapping. While nymphs lack fully developed wings, they develop as the insect matures into an adult.
Common Varieties and Lookalikes
The Brown Marmorated Stink Bug (BMSB), an invasive species, is mottled brownish-gray and approximately 0.67 inches (1.7 cm) long. A key identifying feature for the BMSB is the alternating light and dark bands on its antennae and the alternating dark bands along the thin outer edge of its abdomen. Green Stink Bugs, on the other hand, are typically bright green with narrow yellow, orange, or reddish edges, measuring between 0.5 and 0.7 inches (13 to 18 mm) in length.
Squash bugs, for instance, are often confused with stink bugs due to similar coloring and body shapes, but squash bugs are generally narrower and more elongated. Their abdomens often have orange-brown stripes along the edges. Assassin bugs generally have a more slender head and a visible proboscis, a piercing mouthpart, that is thicker than their antennae.
The Spined Soldier Bug, a beneficial predatory stink bug, can be mistaken for pest stink bugs. However, the Spined Soldier Bug has sharp, outward-protruding spines behind its head and a distinctive dark marking on the transparent part of its forewings that forms a small tail-like appearance when the wings overlap. In contrast, brown stink bugs, which are pests, often have more rounded shoulders.