Homeostasis is the maintenance of static conditions in the internal environment.
Homeostatic mechanisms are active processes because conditions are nearly always subject for forces that will bring about changes. Like virtually all other organisms, terrestrial and aquatic insects confront the problem of maintaining an optimal balance of water and of salts between the intracellular and extracellular compartments. With respect to insects, the most general physiological expression is that ions and water are secreted by Malpighian tubules and they are selectively resorbed in hindguts. Removing excess water from the extracellular compartment is known as diuresis. Most of our information on the regulation of diuresis by DH and ADH comes from research on adult mosquitoes, on the blood-sucking bug Rhodnius and, of course, on the locust.