A series of 11 Autograph Letters Signed, and 1 Typed Letter Signed, to Mr. Ludford, The Four Oaks Spraying Machine Co., Sutton Coldfield, with Ludford’s typed carbon replies, about the manufacture of new appliances for spraying insecticides, with worldwide distribution, atomisers, “backpack sprayers”, demonstration of equipment, the granting of a patent, and much else in technical detail. 22 pp., mostly 10 x 8 inches, in good condition, plus the carbon replies, with some newspaper articles. 1919-1925. Harold Maxwell-Lefroy (1877 –1925) was an English entomologist. He served as a Professor of Entomology at Imperial College London and as the second Imperial Entomologist to India. He left India after the death of two of his children from insect-borne diseases. He worked on applied entomology and initiated experiments on the use of chemicals to control insects. The success of his chemicals led to increased demand and the founding of Rentokil, a company for insecticide production. He was killed in an accident while experimenting on fumigants to control insects.