Theodore Dru Alison Cockerell was born at Norwood, Surrey, 22 August 1866 and died at San Diego, California, 26 January 1948. He was the eldest son of Sydney John Cockerell of Beckenham, and grandson of George Cockerell, a London coal merchant. His mother, Alice Elizabeth, was the daughter of Sir John Bennett, the well-known watchmaker of Cheapside. He was educated at a private school and at Middlesex Hospital Medical School; he was an honorary D.Sc. of Colorado College and of Denver University and Professor of Zoology at Colorado University. He became a naturalized American citizen in 1898, and was elected a member of the Conchological Society in 1921.
Cockerell was very interested in slugs and published many papers thereon in various scientific periodicals. His “ Check-list of the Slugs" appeared in The Conchologist, 2, 1893, and “ A Revised List of the Species of British Slugs “ in this Journal, 7, 1892 He was a prolific writer of notes on Mollusca and as he travelled widely had many observations to record. Later he devoted much of his time to the study of bees, and in 1946 wrote: “ I have been working on African bees: published 41 species of African Halichus in 1945. But to my regret I find no opportunity to work on Mollusca.” Mr. Tomlin writes: " He was a great advocate and coiner of so-called varietal names and for a short time tried to found the expression ‘varietas animalis' for colour forms of the soft parts, admitting distinct varietal names for shell and for animal.”
Cockerell took charge of the Desert Museum, Palm Springs, while Lloyd Smith, the Director, was away on war service, until February 1946. In 1891 he married Annie S. Fenn, daughter of G. Manville Fenn. She died in 1893. In 1940 he married Wilmette Porter, of Iowa.