The ovipositor musculature of Bactrocera depressa Shiraki (Diptera, Tephritidae)

Structure of the ovipositor sclerites and musculature was studied in the tephritid fly Bactrocera depressa Shiraki, whose larvae develop in the fruits of Cucurbita moschata and other Cucurbitaceae. The functioning and adaptations of the ovipositor of this species to laying eggs into soft fruits are discussed with respect to their differences from the ovipositor characteristics in species with different host specializations, e.g., Ceratitis capitata (Wiedemann) (Hanna, 1938), Lenitovena trigona Matsumura (Ovtshinnikova, 2008), Urophora affinis Frauenfeld and U. quadrifasciata (Meigen) (Berube and Zacharuk, 1983) and Campiglossa plantaginis (Haliday, 1833) (Ovtshinnikova, 2010). The ovipositor musculature of Bactrocera depressa is very similar to that of Ceratitis capitata, a species which lays eggs in soft tissues of various fruits. The sclerites and musculature of the ovipositor, especially the basal part of syntergosternite VII, in the fruit infesting Bactrocera (also in Ceratitis) is intermediate between that in Lenitovena laying eggs in the (soft) decaying wood, and Urophora and Campiglossa that deposit eggs in the hard flowerheads of asteraceans. Species of the latter genera have still more complicated structure of the basal part of syntergosternite VII enabling a more intense protruding of the ovipositor and its more closely controlled operating during oviposition in the harder plant tissues. The discussed morpho-functional rearrangements proceed within species of a single lineage of the modern classification (Korneyev, 1999) from the basal Lenitovena to the terminal Urophora and Campiglossa, Bactrocera occupying an intermediate position in this row. In this way, the technology changes (from a muscul lever to a pump) resulting in an increase of the ovipositor mobility during piercing of the substrate.