Antennal Morphology and Ultrastructure of Holotrichia parallela (Coleoptera: Scarabaeidae)

Antennal morphology and type and distribution of antennal sensilla of Holotrichia parallela (Motschulsky) (Coleoptera: Scarabaeidae) were determined using scanning electron microscopy and transmission electron microscopy. Holotrichia parallela antennae were a typical lamellate type, including a basal scape, a pedicel, a flagellum, and a lamellar club composed of the three terminal flagellomeres. The antennae of males were slightly longer than those of females. Twenty-two subtypes of sensilla were identified on the outer and inner surfaces of the lamellae in both sexes: three sensilla trichodea (TRS), three sensilla chaetica (CHS), four sensilla placodea (PLAS), two sensilla coeloconica (COS), six sensilla auricilica (AUS), one Bohm's bristle (BB), and three sensilla basiconica (BAS). TRS, CHS, and BB were distributed primarily on the outer surfaces of the antennae as mechanoreceptor sensilla, while PLAS, COS, AUS, and BAS were concentrated on the inner surfaces of the lamellae as chemoreceptors. PLAS and BAS were more abundant in males than in females, but females had more COS and AUS. PLAS were distributed along the lamellar periphery, while COS, BAS, and AUS were distributed in the center of the lamellae.