Harold Maxwell-Lefroy (20 January 1877 – 14 October 1925) was an English entomologist. He was a Professor of Entomology at Imperial College London who was posted as the second Imperial Entomologist to India. He worked on applied entomology and initiated experiments on the use of chemicals to control insects, founding the Rentokil company.
Maxwell-Lefory was born in the village of Crondall to Charles James Maxwell Lefroy of the 14th Hussars and Elizabeth Catherine McClintock.and attended Marlborough College and King's College, Cambridge, matriculating in 1895 and receiving a BA in the natural science tripos with first class in 1898 followed by a master's degree in 1902.
He served as assistant master of Seaford College, and later worked as an entomologist in Barbados from 1899. In 1903, Lefroy was appointed entomologist to the Government of India (succeeding Lionel de Nicéville, who was the first entomologist, appointed in 1901). Then in 1905 he was involved in the creation of the Imperial Agricultural Research Institute in Pusa, in the Indian state of Bihar, and he was appointed the first Imperial Entomologist.
Lefroy convened a series of meetings on an all-India basis, to bring together all the entomologists of the country. From 1915, five such meetings were held at the Imperial Agricultural Research Institute, and these formed the foundation of entomological knowledge in India. He was succeeded in the position of Imperial Entomologist by T. Bainbrigge Fletcher. He published Indian Insect Life, a summary of the major insects of economic importance in 1906, in association with Frank Milburn Howlett.
In the early 1920s, Lefroy was asked by Sir Frank Baines, Principal Architect of the Office of Works, to study ways of exterminating death watch beetles that had been found in Westminster Hall, beside England's Houses of Parliament. As a result, he went on to devise various successful formulations for pest control, and in time Lefroy began receiving regular orders from people who had heard about his work. In 1924, Lefroy and his assistant Miss Elizabeth Eades started supplying bottles of woodworm fluid from a small factory in Hatton Garden, which later led to the formation by them of a company called Rentokil Limited (now Rentokil Initial) in 1925.
Lefroy was killed by poisonous fumes in a laboratory accident in October 1925. It is thought that he was experimenting with Lewisite. Lefroy married Kathleen Hamilton O'Meara, second daughter of a provost-marshal in British Guiana. They had three children Gladys Kathleen, Charles, and Cecil Anthony Maxwell Lefroy (later CBE).
- Indian Insect Pests (1906)
- Maxwell-Lefroy, H. 1909. Indian Insect Life: a Manual of the Insects of the Plains (Tropical India) Thacker and Spink, Calcutta. xii + 786 pp.
- Maxwell-Lefroy, H. 1910. List of Names Used in India for Common Insects Indian Agricultural Research Institute, Pusa, India. iv + 47 + xii pp.
- Manual of Entomology 1923
- Food of Birds in India (1911) C. W. Mason and Maxwell-Lefroy
- "Maxwell-Lefroy, Harold (MKSL895H)". A Cambridge Alumni Database. University of Cambridge.
- John L. Capinera (2008). Encyclopedia of Entomology. Springer Science+Business Media. ISBN 978-1-4020-6242-1.
Harold Lefroy was born on January 20, 1877, ... King's College, Cambridge ...
- Western Daily Press. 15 October 1925. p. 12 http://www.britishnewspaperarchive.co.uk/viewer/bl/0000264/19251015/128/0012 – via British Newspaper Archive. Missing or empty
- Fox-Davies, Arthur Charles, ed. (1929). Armorial families : a directory of gentlemen of coat-armour (7 ed.). London: Hurst & Blackett. p. 1157.