C.B. Simpson qualified as Bachelor of Science (BS) at the University of Idaho in 1898. Continuing his studies in entomology at Cornell University, New York State, he obtained the degree Master of Arts (AM) in 1900. That same year he was appointed in the Division of Entomology of the United States Department of Agriculture, where he established an enviable reputation as a field investigator. His work related mainly to the codling moth as an agricultural pest and led him to publish a monograph, The codling moth (Washington, 1903), as well as reports on his investigations of this pest in Idaho (1901) and in the north-west of the country (1902). In 1903 the government of the Transvaal Colony asked the Chief of the Division, L.O. Howard, to recommend a suitable person for the new post of government entomologist of the Transvaal. Howard recommended Simpson, who was appointed as the first Chief of the Division of Entomology in the Transvaal Department of Agriculture, assuming duty in August 1903. Before leaving the United States he requsted an advance from the Transvaal government to buy some technical books. Upon his arrival he first spent several weeks with the government entomologists of the Cape Colony (Charles P. Lounsbury*) and Natal (Claude Fuller*) before settling in Pretoria. He held his position until his death early in 1907, and showed considerable energy and ability.
As the first professional entomologist in government employ, Simpson made a significant contribution to the early development of economic entomology in the Transvaal. Within the first year he published two articles and some notes in the Transvaal Agricultural Journal and from July 1904 to July 1906 wrote the Entomological Section of this quarterly publication. By 1906 he was a member of the South African Association for the Advancement of Science. At this time he had a collection of identified South African mosquitoes. Shortly after being married to Annie B.U. Perrin, he died in his post of enteric fever. C.W. Howard* succeeded him as government entomologist, though for a short period only.