Stink bugs are known for their distinctive odor, released when disturbed. This potent scent is “coriander-like,” “pungent,” or even resembles “burnt rubber.” Not everyone perceives this odor similarly, raising the question of whether some individuals cannot smell stink bugs at all.
The Chemistry of the Stink Bug Odor
The unique smell of stink bugs comes from defensive secretions containing specific chemicals. These aldehydes, trans-2-decenal and trans-2-octenal, are major contributors to the scent. Stink bugs release these chemicals from glands on their abdomen, deterring predators.
Each aldehyde contributes different notes. Trans-2-decenal is described as waxy, fatty, or fried, with hints of coriander, cilantro, mushrooms, or floral notes. Trans-2-octenal has a nutty, waxy, or cucumber-like aroma, with fresh green and herbaceous undertones. Combined, these compounds create the strong, often unpleasant odor. These chemicals are also found in cilantro, explaining why some who dislike cilantro’s taste find the stink bug odor offensive.
The Science Behind Olfactory Differences
Differences in stink bug odor perception stem from variations in human olfaction, a complex sense relying on olfactory receptors. Humans have approximately 400 intact olfactory receptor genes. Their genetic makeup varies significantly. These variations, called polymorphisms, alter how odor molecules are detected.
Specific anosmia is one reason some people may not smell stink bugs. This is the inability to detect a particular odorant, or reduced sensitivity, while other smell functions remain intact. It differs from general anosmia, a complete loss of smell. For stink bugs, an individual may lack the precise olfactory receptor to bind effectively with trans-2-decenal and trans-2-octenal, or their receptors may be less sensitive.
Specific receptor variants directly influence how these chemicals are perceived. Research shows genetic variations in olfactory receptor genes lead to substantial differences in odor perception; two individuals can differ functionally at over 30% of their olfactory receptor alleles. Some individuals may have a receptor variant that does not respond to stink bug chemicals, or responds very weakly, leading to little to no odor perception. This is comparable to color blindness, where genetic variations in visual receptors alter color perception.
Beyond complete inability to smell, perceptual thresholds vary among individuals who detect the odor. A detection threshold is the minimum odorant concentration required to detect its presence, even without identification. The recognition threshold, a higher concentration, is where the odor is clearly identified. These thresholds are not fixed and vary significantly due to unique genetic predispositions and olfactory system sensitivity. Even among those who perceive the stink bug smell, some are far more sensitive than others.