Although best known for his work in freshwater biology, his first job (1933–34) was on a scientific expedition to the Indian Ocean.
In 1941, he was commissioned as Lieutenant into the Royal Army Medical Corps,;[1] he subsequently rose to the rank of Major; he addressed problems relating to malaria in Iraq, Iran, India and Burma.
He then concentrated on a detailed taxonomic study of the British Ephemeroptera (mayflies), culminating in the publication in 1961 of the first complete guide to their nymphs (most recent edition 1979).
His principal locations of study were in Ford Wood Beck, a small stony stream near his home in Outgate near Hawkshead, Cumbria; and in Hodson's Tarn, a moorland lake close to the Windermere Laboratory of the FBA.
He was a prolific author of scientific papers and books; his Life in Lakes and Rivers (co-authored with E. B. Worthington) was at one time a set text in the Open University.