Malpighian tubule Any of the organs that are involved in the excretion of nitrogenous waste in insects, arachnids, and centipedes. They lie in the haemocoel. In insects Malpighian tubules open into the intestine; they selectively extract from the blood uric acid, which – together with water and salts – is deposited into the hindgut and excreted in the faeces. Some reabsorption of water and salts can occur in the tubule itself but most reabsorption occurs in the hindgut. See also cryptonephridial system.

Malpighian tubules The excretory organs of insects. They are long and narrow, made up of transporting epithelial cells, which join the gut at the junction of the mid- and hind gut. When stimulated hormonally they produce copious amounts of isotonic urine. Their numbers vary greatly from species to species.