After serving parishes for 9 years, he was appointed headmaster of Trinity College School, Port Hope, which he turned into one of the most prestigious boys' schools in Canada.
As professor and head of the entomology department at the Ontario Agricultural College (now part of University of Guelph) 1906-20, he pioneered the instruction of the science of insects at the university level. Always an ardent collector of insects, he cofounded with William Saunders the Entomological Society of Canada in 1863, served for 11 years as its president and edited its journal, the Canadian Entomologist, for about 30 years. At Guelph he developed the teaching of economic entomology based on sound scientific principles, promoted the collection and careful identification of insects, and published widely on the lives of insects and on their control.