Scanning Electron Microscopy Characterization of the Antenna in Males of Mesomorphus villiger (Blanchard, 1853) (Coleoptera: Tenebrionidae)

The tobacco ground beetle, Mesomorphus villiger (Blanchard, 1853) (Coleoptera: Tenebrionidae), is a widely distributed species across Asia, Africa, and Australia, recognized for its economic importance as a pest of tobacco seedlings and other crops in India. Despite its pest status and characteristic aggregation behavior, information on its antennae and antennal sensory structures remains limited. In this study, the morphology of the antennae and the types and distribution of antennal sensilla in M. villiger males were examined using scanning electron microscopy. The antennae had 11 segments, including a scape, a pedicel, and a flagellum, with the last three flagellomeres forming a club. Six types of sensilla were identified: Böhm’s bristles, sensilla chaetica (two subtypes), sensilla trichodea, sensilla basiconica (three subtypes), sensilla auricillica (two subtypes) and grooved peg sensilla. The structural characteristics and distributional patterns of the sensilla suggest functional specializations for olfactory, mechanoreceptive, and chemioreceptive roles. Sensilla diversity progressively increased from proximal to distal antennal regions, with the highest number of types observed on the club. This study provides the first comprehensive ultrastructural description of the antennae and antennal sensilla in M. villiger males, establishing a morphological foundation for future electrophysiological and behavioral investigations to be extended to females and supporting the development of innovative management strategies for this species.