Simon Maddrell made elegant contributions to the study of the excretory system of insects, devising improved techniques for measuring secretory activity of Malpighian tubules in vitro. He discovered the existence of a diuretic hormone in Rhodnius, derived from neurosecretory cells in the thoracic ganglia and liberated commonly by exocytosis, from axon terminations along the abdominal nerves. He found that many insecticides induce release of diuretic hormone and this may be one reason for their effectiveness. Neurohormones were also shown to control the plasticity of the cuticle. Simon’s methods have been widely employed in the search for hormones affecting insect water balance, as well as many epithelial transport processes.

Professor Simon Maddrell FRS died on 10 September 2020.