Ultrastructural studies on the midgut of biting midge Forcipomyia nigra (Winnertz) (Diptera: Ceratopogonidae).

Biting midges belonging to the genus Forcipomyia are known to be hematophagous, predatory or saprophagous. Different stages of Forcipomyia nigra midges were investigated to provide a description of midgut ultrastructure. Larvae feeding on decaying organic matter possess simple, straight alimentary tracts whose middle regions are the longest. TEM studies of the larval midgut epithelium reveal that digestive cells show different ultrastructure depending on their age. The older cells with electron-dense cytoplasm degenerate while the younger ones with electron-lucent cytoplasm remain active in digestion. In saprophagous females, the ultrastructure of midgut epithelium changes according to the age of flies. Oogenesis induces degeneration of digestive cells and utilization of reserve material accumulated by them. The midgut epithelia of male midges consist of digestive and regenerative cells that show no evidence of cell degeneration as observed in females. Our results demonstrate differences between midgut digestive cells of males and females.