Microscopic and ultrastructural studies of the ileum of anisopteran larvae reveal the existence of thick and thin epithelia. The thick epithelium apparently is organised for ion transport. The cells are covered with a multilayered cuticula. The apical cell membrane is much folded. Many mitochondria occur beneath these foldings. The basal cell membrane is also folded and closely associated with mitochondria. The lateral cell membranes are simularly folded. Septate desmosome structures are present. Transporting epithelia in the anterior part of the hindgut may play an important role in the osmoregulation of the haemolymph of the larvae by reabsorbing ions from the urine, produced by the Malpighian tubules.