Stink bugs, members of the insect family Pentatomidae, are familiar, if unwelcome, visitors in homes and gardens. These shield-shaped creatures are recognized as agricultural pests and nuisance home invaders, especially when seeking shelter indoors to overwinter. Their presence often sparks curiosity about their basic biology and the unique defense mechanism that gives them their common name.
Six Legs: The Defining Feature of Insects
A stink bug possesses six legs. This specific number is the defining trait that classifies it into the Class Insecta, a group also known as Hexapoda, which literally means “six legs”. These six appendages are arranged in three pairs, with each pair extending from one of the three segments of the thorax.
The legs are segmented, allowing for articulation and movement, and they terminate in specialized tarsi and claws. The three pairs of legs provide the stable, tripod-like gait characteristic of most adult insects.
Anatomy Beyond the Legs
Beyond the six legs, the stink bug’s body is divided into three distinct sections: the head, the thorax, and the abdomen. The family name, Pentatomidae, refers to their characteristic broad, shield-like shape. The most prominent feature is a large, triangular plate called the scutellum, which extends over a significant portion of the back.
The head holds a pair of antennae, typically composed of five segments. Crucially, the head also contains the piercing-sucking mouthparts, known as the proboscis or rostrum. This specialized structure is deployed to pierce plant tissue, allowing the bug to extract sap or juices. Adult stink bugs are also equipped with wings, which are folded flat over the abdomen and enable them to fly effectively.
The Source of the Stink
The unpleasant odor for which the stink bug is famous is a defense mechanism used to deter predators. This foul scent is produced by specialized glands located on the underside of the insect’s body. In adult stink bugs, these scent glands are positioned on the thorax, specifically between the first and second pair of legs. The chemical mixture is released through small openings in the exoskeleton when the bug is disturbed, handled, or crushed.
The primary components of this defensive spray are volatile organic compounds, specifically aldehydes like trans-2-decenal and trans-2-octenal. This chemical composition prompts many people to describe the odor as smelling distinctly like strong coriander or cilantro.