Morphological Characterization and Distribution of Antennal Sensilla of Six Fruit Flies (Diptera: Tephritidae)

Fruit flies (Diptera: Tephritidae) are important pests of many fruits and vegetables. In this study, the external morphology, types, and distribution of antennal sensilla in both male and female adults of the six fruit fly species, including Bactrocera tau (Walker), Bactrocera dorsalis (Hendel), Bactrocera cucurbitae (Coquillett), Bactrocera minax (Enderlein), Bactrocera diaphora (Hendel), and Bactrocera scutellata (Hendel), were observed by using scanning electron microscopy. The antennae of the six fruit fly species consist of a basal scape, pedicel, and an elongated flagellum. Arising from the proximal dorsal ridge of flagellum there is an arista consisting of two short basal segments and a long thin distal segment. Six distinct morphological types of sensilla are recorded in both sexes, including microtrichial sensilla, sensilla chaetica, sensilla trichoid, sensilla basiconica, short type of sensilla basiconica, and sensilla coeloconica. The abundance and distribution of these six sensilla types on the antennae of both sexes are recorded. In addition, the possible functions of the above-mentioned sensilla types are discussed in light of previously published literature. The functions include the mechanoreception of microtrichial sensilla, sensilla chaetica, and sensilla trichoid; olfactory functions of sensilla basiconic, and sensilla coeloconica; and thermoreception of the short type of sensilla basiconica. Future functional antennal morphology and electrophysiological studies are needed to confirm these proposed functions.