Stink bugs are small insects, often shield-shaped, recognized for their unusual ability to release a distinct, unpleasant odor. This characteristic smell is the reason behind their common name and serves as a primary defense mechanism. While they may appear harmless, their odor can be quite potent, leading many to wonder about its origin and purpose.
The Chemical Signature
Stink bugs possess specialized glands that produce the compounds responsible for their characteristic smell. These glands are located on the underside of their thorax and dorsal surface of the abdomen. When disturbed, these insects can release a fluid containing chemicals through small pores. The primary compounds contributing to the odor are aldehydes and esters, particularly trans-2-decenal and trans-2-octenal. These compounds quickly evaporate, creating the noticeable smell.
While these aldehydes are the main contributors, the specific chemical composition can vary among different stink bug species. For instance, trans-2-decenal is often described as having a “powerful waxy orange aroma,” and trans-2-octenal may have a nutty or waxy scent, sometimes resembling cucumber. Despite individual notes that might seem tolerable in isolation, their combination results in the offensive odor.
Purpose of the Pungent Release
The pungent odor released by stink bugs serves primarily as a defensive mechanism. This chemical deterrent helps protect them from predators. Stink bugs release their smell when threatened, handled, or crushed. The sudden release of this strong scent makes the bug unappetizing or unpleasant to a potential attacker.
Beyond deterring direct threats, the odor can also act as an alarm signal to other stink bugs. Some chemicals released, known as aggregation pheromones, can attract other stink bugs to an area, potentially indicating a safe overwintering spot or a food source. This dual function highlights chemical communication within these insects.
Perceiving the Odor
The human perception of the stink bug’s odor varies, but it is generally considered unpleasant. Many people describe the smell as similar to cilantro or coriander, while others liken it to burnt rubber, strong herbs, or a sour, fermenting apple. Some individuals may perceive it as having a sulfurous or rancid quality. The specific chemical blend and individual olfactory senses contribute to these differing descriptions.
While the odor is strong, it is generally not considered harmful or toxic to humans or pets. The fluid released is not poisonous, though it can cause temporary skin irritation in sensitive individuals upon direct contact. Ingesting a stink bug, while unappealing, typically causes only mild symptoms like upset stomach or mouth irritation in pets. The smell itself can linger on surfaces or in the air for hours or even days, particularly indoors.