Career
Born in Cushendall, Company Antrim, he was one of two sons of James Delargy and Mary Josephine McQuillan. Following the death of James Delargy the family moved to Glenariff, Company Antrim and later to Company Wicklow. Graduating with a degree in Celtic Studies from University College Dublin, he founded the Folklore of Ireland Society in 1926 and was involved with the foundation of its magazine "Béaloideas" the following year.
He would remain its editor until his retirement.
In 1930 the Society became the Irish Folklore Institute and received a government grant, and in 1935 the Irish Folklore Commission (Coimisiún Béaloideasa Éireann) was established in University College Dublin by the first Fianna Fáil government. Ó Duilearga was appointed director and Seán Ó Súilleabháin (1903-1996) a Kerryman, was the appointed archivist.
The Commission operated under the aegis of the Department of Education, and aimed to collect, preserve and classify all aspects of Irish folk tradition in a systematic manner. One of its first projects was the Schools’ Collection Scheme 1937, which was a voluntary nationwide attempt to rescue "from oblivion the traditions…of the historic Irish nation.’ Operated through the National Schools system, it resulted in a collection of about a half a million manuscript pages of folklore, now housed in the Department of Irish Folklore at University College Dublin.
Ó Duilearga was appointed lecturer in Irish in University College Dublin in 1923, and later that year he was visiting Seán Ó Conaill in Kildreelig, south-west Kerry, when he encountered the Swedish folklorist Carl Wilhelm von Sydow.
He subsequently negotiated a sabbatical from University College Dublin to study folklore in Lund and Uppsala. He was made lecturer in folklore in University College Dublin in 1934, and Professor of Folklore in 1946, while continuing to serve as Director of the Folklore Commission. He resigned his University College Dublin chair in 1969, retired from the Commission in 1971, and died in Dublin in 1980.