Charles William Mally, economic entomologist, grew up on a maize and stock farm in Iowa. He studied entomology at the Iowa State College of Agriculture and Mechanic Arts, graduating as Master of Science (MS) in 1894, but was interested in natural history in general. Subsequently he worked at the State Agricultural Experiment Station of Ohio, where he was chief assistant to Professor M.F. Webster, one of the foremost American economic entomologists at that time. At the beginning of his career he published, among others, two papers on Psyllidae (so-called jumping plant lice) found at Ames, Iowa in the Proceedings of the Iowa Academy of Sciences (1894, 1895).
Mally came to the Cape Colony in February 1900 to take up an appointment as assistant entomologist (under C.P. Lounsbury*) in the Department of Agriculture at Cape Town, a post previously occupied by Claude Fuller*. At this time he worked mainly on the development of insecticides. In September 1903 he was sent to the Eastern Cape to serve as assistant entomologist there, following representations from that region for the services of an entomologist to help combat insect pests. He was stationed at the Albany Museum, Grahamstown, and in 1904 his post was upgraded to Eastern Province entomologist. During this period he investigated measures to combat the maize stalk borer, fruit fly and locusts, and published several papers in the Agricultural Journal of the Cape of Good Hope: "Notes on the so-called paralysis tick, Ixodes pilosus" (1904, Vol. 25, pp. 291-296), in which he provided the first published record of tick paralysis in South African animals; a detailed paper on "The fruit fly (Ceratitis capitata, Wied.)" and its control (1904, Vol. 25, pp. 647-662); "The destruction of locusts" (1905, Vol. 26, pp. 406-420); and "The mealie stalk-borer" (1905, Vol. 27, pp. 159-168). He acted as honorary curator of the Albany Museum's entomological collections and studied the habits and life histories of local insects.
In 1905 the Cape government reorganised the Department of Agriculture and, fearing that he might be retrenched, Mally resigned at the end of 1905 to return to the United States. At first he settled in Garrison, Texas, but soon accepted a post in the Ohio state service. However, he returned to Grahamstown in 1907 to take up his previous post, which had been filled by W.R. Dewar*.
After the formation of the Union of South Africa in 1910 Mally was transferred to Cape Town in 1911 as government entomologist for the Cape Province. He was promoted to senior entomologist in 1919. In 1922 he prepared very finely pulverised dry arsenite of soda, developed a small dusting machine with which to distribute it, and demonstrated its effectiveness in destroying locusts. The powder was widely used by the government to combat wingless locusts in regions where water for spraying was not available, and was also adopted for distribution by aeroplane. In recognition of his work in economic entomology the University of Stellenbosch awarded him an honorary Doctor of Science (DSc) degree in Agriculture in 1924. Lounsbury (1940), his former chief, later wrote of him: "A harder working and more industrious entomologist this country has never had".
Mally collected fungi, which were later taken up in the National Collection of Fungi of the Plant Protection Research Institute (part of the Agricultural Research Council) in Pretoria. In due course he was elected a Fellow of both the (British) Entomological Society and the Linnean Society. He became a member of the South African Philosophical Society in 1900, remained a member when it became the Royal Society of South Africa in 1908, was elected a Fellow of the society in 1917, and served on its council during 1919-1920 and in 1924. By 1903 he was a member of the South African Association for the Advancement of Science and in 1908, when the association held its annual meeting in Grahamstown, delivered three (unpublished) entomological papers. In later years many papers by him were published in the association's annual Reports, including "Notes on the use of poisoned bait for controlling the house fly, Musca domesica, L." (1914); "Anhydrous liquid hydrocyanic acid for fumigation purposes" (1915); "On the selection and breeding of desirable strains of beneficial insects" (1916); "Finely powdered mercuric chloride for the destruction of the Argentine ant, Iridomyrmex humilis Mayr." (1916); "A convenient type of hydrocyanic gas generator for the destruction of the mealy bug, Pseudococcus capensis Brain" (1916); "The Woolly Aphis (Eriosoma lanigera) as a factor in apple culture" (1917); and "On the persistence of arsenide of soda in the soil" (1918). As president of Section D of the association in 1920 he spoke on "Some zoological factors in the economic development of South Africa". In 1908 he joined the South African Ornithologists' Union and when the Union was incorporated into the new South African Biological Society in 1916 became a foundation member of the latter. He was an examiner in entomology for the final year of the BSc Agriculture examinations of the University of the Cape of Good Hope in 1916.
In 1926 Mally was was appointed as a lecturer at the Elsenburg Agricultural College, University of Stellenbosch, while retaining his post as senior entomologist in the Division of Entomology of the Department of Agriculture. He then conducted research on the use of raw linseed oil to combat delayed foliation in fruit trees, and on the use of hydrogen cyanide to treat white aphid in vineyards. After his retirement in 1932 he held temporary appointments at Cape Orchards and at African Explosives and Chemical Industries. He was married to Annie (or Anna) Ayres, with whom he had three children who all died before him.