Histological Structure of the Clypeo-Cibarial and Labral Skeleton and the Musculature in the Lower Asilomorpha(Diptera): 2. Stratiomyoidea

摘要

The superfamily Stratiomyoidea is characterized by a highly diverse structure of the mouthparts and the clypeal part of the head capsule. Xylomyia has an immovable clypeus rigidly merged with Irons and genae and a short proboscis with restricted mobility. In most Stratiomyoidea, the clypeus is longitudinally subdivided into five zones: medial centroclypeus, two lateral membranes located on its sides, and two lateral sclerotized zones adjoining the anterior tentorial pits. The mobility of stratiomyid centroclypeus is determined by the width of the lateral membranes and the presence of a so-called dorsal hinge, a weakly sclerotized integumental stripe at the proximal end of the centroclypeus. Poorly developed lateral membranes, a short centroclypeus, and a short and weakly movable proboscis are characteristic of most Beridinae and all the studied members of Pachygasterinae and Sargi-nae. Some species of Stratiomyinae and Clitellarinae have a long narrow clypeus, wide lateral membranes, and a longfolding proboscis. Owing to the shift of clypeus to the ventral side of the head, the proboscis elongates significantly as it is unfolded and its distal part moves forwards. The clypeus becomes more mobile due to the development of clypeal ridges as supporting structures. The latter are transformed into large plates which merge with the cibarium to form a rigid cuticular skeleton, the fulcrum. The mobility of the fulcrum creates conditions under which the typical anterior pharyngeal pump cannot function, and the pharynx is progressively replaced by the oesophagus.