Light and electron microscopicexamination of the midgut Wohlfhrtia nuba revealed 7 differentiated portions along its epithelium.The anterior portion of the midgut was considered as an important site for absorbtion of nutrients.The posterior midgut,especially its proximal portion,can be considered as an impotant site of accumulation and secretion of secretory vesicles. On the other hand ,the mosaic A andBcells of the middle midgut may be primarly involved in lowering its Ph.According to location,shape,and electron density of cytoplasm,there are two ultrastructurally distinct endocrine cell types (closed and open) in the middile and posterior midgut.