Histological structure of the mouthparts, clypeo-cibarial system, and cephalic foregut in Philoliche rondani (Diptera, Tabanidae, Pangoniinae)

Abstract

The leading factor responsible for the evolution of Philoliche rondani mouthparts, as well as those of the other long-proboscid Pangoniinae, appears to be adaptation to the intake of nectar from concealed sources (flowers with elongated floral tube). Adaptations to blood-sucking, inherent only in females, have morphogenetic and behavioral aspects. Philoliche rondani males, as compared to males of Tabanus-like species, have better developed clypeus, labrum, and labium. The presence of a long proboscis has led to transformation of the labial musculature and complication of the food canal structure. During the intake of nectar, the distalmost portion of this canal is formed only by the labium. The lateral labial folds form a peculiar closing apparatus. The cibarial and pharyngeal pumps of Philoliche rondani are similar to those of other tabanids investigated.