Morphology and Chemical Characterization of the Metathoracic Scent Gland in Halyomorpha halys (Stål, 1855) (Hemiptera: Heteroptera: Pentatomidae)

ABSTRACT Halyomorpha halys (Stål, 1855) is an invasive pentatomid species causing considerable economic losses in agricultural systems. Despite the ecological importance of the metathoracic scent gland (MTG) in chemical defence and communication, detailed information on its morphology and secretion composition remains limited. In the present study, the MTG of adult males and females was examined using stereomicroscopy, light microscopy, scanning electron microscopy (SEM) and gas chromatography–mass spectrometry (GC–MS). The gland consisted of a single‐lobed reservoir associated with paired lateral glands, ostiolar openings and a well‐developed evaporatorium. Scanning electron microscopy revealed a porous band‐like structure embedded within the reservoir wall and an evaporatory surface densely covered with mushroom‐like cuticular bodies interconnected by trabeculae. A distinct channel‐like structure extending from the ostiole was also observed. GC–MS analysis identified 10 compounds in males and 11 in females, with trans‐2‐decenoic acid as the predominant component in both sexes, whereas several minor constituents showed sex‐associated variation. These findings provide a comprehensive morphological and chemical characterization of the MTG in H. halys , expanding current knowledge of scent gland organization in Pentatomidae and providing a morphological framework for future comparative and functional studies.