Functional morphology of the proboscis of the fly Prosena siberita (Diptera, Tachinidae)

Functional morphology of the proboscis of the fly Prosena siberita
(Diptera, Tachinidae). The flower-visiting behaviour and mouthpart morphology were studied in the long-proboscid fly Prosena siberita (Fabricius, 1775) (Tachinidae) for the first time using light microscopy and scanning electron microscopy. Prosena siberita visits inflorescences to extract nectar. The proboscis consists of the basal rostrum and the long haustellum, which measures about half the body length. In resting position, the conspicuously thin haustellum points forward. The haustellum articulates with the extensible rostrum, where it can be folded downward for feeding. In the proximal haustellum, the u-shaped labrum-epipharynx unit forms the food canal along with the rod-shaped hypopharynx. Both components are surrounded from posterior by the laterally bent up prementum of the labium. In the distal haustellum, the prementum is tubular and forms the food canal; labrum and hypopharynx do not reach this section. At the tip, the short labella are directed forward. The labella form a gap leading to three longitudinal pseudotracheae which merge with the food canal in the prementum. Only a few other representatives of the Tachinidae have proboscises longer than the head. Some of these long-proboscid tachinid flies possess proboscises with long labella, which are foldable backwards. These findings suggest independent evolution of particularly long proboscises within Tachinidae.