John Cecil "Zoo" Le Souëf, the son of William Henry and Edith Le Souëf was born in a sleep-out at the Melbourne Zoo on 5 November 1905. His life-long nickname, acquired at Kindergarten, was attributed to his family's association with the Melbourne Zoo. Unlike the generation preceding him, Cecil's career assumed a different and more varied direction. Educated at Melbourne Grammar School, Cecil was employed as a cashier for Dalgety and Company. In 1927 he retraced his grandfather's steps and worked briefly as a jackeroo in the Riverina and Queensland. In the following year Cecil moved to Sydney where he married Dumel White Fisher and worked as a commercial traveller.

On the couple's return to Melbourne in September 1932, Cecil was employed by the ABC on publicity work and presenting a children's program entitled "Zoo Talk" on 3LO. Unfortunately in the midst of the depression, the ABC were forced to reduce staff and terminated his services in 1934. Concurrently in 1933 Cecil Le Souëf was appointed correspondent on natural history with The Star, a small newspaper affiliated with Argus. Employed to cover the zoo and any "good human interest stories", Cecil was also asked to write a ‘Nature Note' once a week. Several months later the editor cancelled the agreement citing duplication because the newspaper had an existing contract with Arthur Wilkie, the Director of the Melbourne Zoo

For the remainder of the decade and with his unfailing optimism, Cecil attempted several unsuccessful entrepreneurial ventures. In 1934 he acquired 56 acres at Belgrave and created Le Souëf's Fauna Park. In the following year he became involved in a film company and in 1938, Cecil Le Souëf floated another company to build an aquarium on the St. Kilda foreshore. After brief negotiations with the Council, he reconsidered citing structural difficulties. Undaunted, in 1939 Cecil attempted to establish another fauna park in Sandringham. The 1930s also proved difficult for Cecil on a personal level. In 1935 his seven year marriage broke down acrimoniously and the divorce was finalised in 1941.

Despite these disappointments Cecil continued to work as a freelance journalist and writer. Enthralled by natural history, particularly insects, he developed an enduring reputation as one of the great amateur entomologists. In 1941 Cecil joined the Entomologist Society and was elected secretary in 1942 until it was disbanded later in the year due to the war. When the Society was reformed in 1961 it was Cecil Le Souëf who was credited with its re-emergence. His infectious enthusiasm guided the Entomologist Society through several lean periods and his legacy is a thriving group of entomologists in Victoria. Cecil Le Souëf also traveled extensively throughout Australia in pursuit of different types of insects and moths. Credited with discovering on Mt. William in the Grampians the species Hesperilla Crypsargyra or Mountain Skipper and in 1980 Cecil found and described another species in the Darwin region. In later years his main entomological activity was a study of the lycaenid genus Ogyris, of which he reared many specimens from remote parts of Queensland and New South Wales.

In 1941 Cecil married Katherine Mary Clarke who shared his passion for entomology. The couple settled in Kyabrum where they owned a cordial factory until 1953 when they moved to Blairgowrie to run a general store. In 1960 the Le Souëfs established the Rosebud Aquarium which has been in recent years operated by their son Nicholas. Cecil Le Souëf was also a prominent identity in the community; he was appointed the Honorary Justice of the Peace, served on the Sorrento Court bench and was involved in Rotary receiving their highest honour, the Paul Harris Fellow.

After a period of illness, Cecil Le Souëf died on 21 June 1982. He was survived by his wife, son and three grandchildren.