A box elder bug is not a stink bug, although the two insects are often confused by homeowners who find them clustering near their homes in the fall. Both species are classified under the same taxonomic Order, Hemiptera, meaning they are both considered “true bugs” and share piercing-sucking mouthparts. Despite this shared classification, they belong to entirely separate insect Families. The box elder bug belongs to the family Rhopalidae, sometimes called scentless plant bugs, while the true stink bug belongs to the family Pentatomidae. These family differences mean they are biologically and physically distinct.
Anatomy and Life Cycle of the Box Elder Bug
The box elder bug, scientifically known as Boisea trivittata, is identified by its striking appearance. The adult measures about one-half inch long and features a dark brown or black body with distinct red or orange markings. These markings include three longitudinal red stripes on the thorax and red piping along the edges of the wings. When the wings are folded, the reddish markings often create a noticeable ‘X’ pattern across the back.
Box elder bugs undergo an incomplete metamorphosis, progressing through three stages: egg, nymph, and adult. Females lay reddish-brown eggs in the spring, typically in crevices on the bark of their host trees. The nymphs that hatch are bright red and wingless, gradually developing black markings as they mature. The insects are named for their primary food source, the seeds and sap of the box elder tree (Acer negundo), though they will also feed on other maples and ash trees.
As temperatures drop in the fall, adults aggregate in large numbers on warm, sunny surfaces, like the south-facing sides of homes. They do this before seeking protected places to overwinter.
Defining the True Stink Bug
The stink bug is a member of the insect family Pentatomidae, a group that includes over 4,700 species worldwide. This family is defined by the characteristic, broad, shield-shaped body of the adult insect. They typically range from about one-third to three-quarters of an inch in length and have a large triangular plate, known as the scutellum, situated in the center of their back.
The name “stink bug” comes from their chemical defense mechanism. When threatened or crushed, they release a foul-smelling compound from specialized glands located on the underside of their body. This odor is an effective deterrent to predators and is a key distinguishing feature. Their diet is diverse; most species are herbivorous, feeding on fruits, vegetables, and ornamental plants, which can cause significant crop damage.
Key Differences in Appearance and Behavior
The most immediate difference between the two insects is their overall body shape. The box elder bug is narrow and elongated, while the stink bug has a distinctly wide, shield-like, or pentagonal shape. Box elder bugs have a consistent coloration of black with bright, distinctive red or orange lines and markings. In contrast, common stink bugs, such as the brown marmorated stink bug, are typically mottled brown, green, or gray, allowing them to blend into bark and foliage.
The nature of their odor also differs significantly. A box elder bug emits a mild, sometimes staining, odor only when it is crushed or killed. The stink bug, however, releases a strong, persistent chemical defense spray from its glands when it is disturbed or feels threatened. Furthermore, their feeding habits diverge. The box elder bug specializes in the seeds and sap of specific trees like the box elder, while many stink bug species are generalist feeders that can damage a wide variety of commercial crops.