Mouthpart structure of the adult Bicaubittacus appendiculatus () (Mecoptera: Bittacidae)

The structure and functional morphology of the mouthparts were investigated in adult hangingfly Bicaubittacus appendiculatus (Esben-Petersen, 1927) by scanning electron microscopy and histological serial sections. The mandibulate mouthparts consist of a labrum-epipharynx, paired mandibles and maxillae, and unpaired labium and hypopharynx. The labrum is elongated and tapered toward the apex. The epipharynx is furnished with numerous sensilla. The mandibles are sword-shaped, with an outer sharp tooth curved mesad and an inner blunt corner. The basal region of each mandible processes a conical projection. The maxillae are well-developed, each consisting of a sclerotized cardo, an elongated stipes, which bears an inner lacinia, an outer galea, and laterally a five-segmented maxillary palp. The labium is formed by a postmentum, a prementum and a pair of two-segmented labial palps. The hypopharynx is concave inward on the anterior side, with numerous microtrichia on the posterior surface. Seven types of sensilla were found on the mouthparts: sensilla basiconica on the epipharynx, and maxillary and labial palps; sensilla chaetica on the epipharynx; sensilla palmata, sensilla placoidea and sensilla trichodea on the epipharynx and maxillary palp; sensilla campaniformia and hair plates on the basal joints of palps. The sensillar function and the feeding mechanism of mouthparts in bittacids are briefly discussed.