Ecologist and entomologist who drew attention to the environmental effects of pesticides. Born in Barrhead (East Renfrewshire), Mellanby spent most of his life away from Scotland. He was educated at Barnard Castle School (Co. Durham), King's College, Cambridge and the University of London. Between 1935 and 1945, he worked in medical entomology at the London School of Hygiene and Tropical Medicine taking the opportunity of his military service during the Second World War to study typhus in Burma (now Myanmar) and New Guinea. He helped create the first university in Nigeria, at Ibadan, becoming its first Principal (1947-53). He was appointed Head of the Entomology Department at Rothamsted Experimental Station in 1955. Mellanby founded the Monks Wood Research Station (Huntingdon, Cambridgeshire) in 1961, becoming its Director. Here he led research into the effects of pesticides on the environment, advocating biological control, using predators to eat the pests, as a safer alternative. He wrote the pioneering book Pesticides and Pollution (1967) and founded the journal Environmental Pollution in 1970.
Mellanby was awarded a CBE and his name survives in Mellanby Hall at the University of Ibadan.