Worked in the National Museum, Dublin, from 1922 as Technical Assistant (although he took charge of the zoological collections between 1924 to 1930) where he was much influenced by A.R.Nichols and J.N.Halbert. Perhaps best known for his later work on Mallophaga and Siphonaptera of which he compiled a Catalogue of the Irish species, but he also wrote some fifty articles on Irish Coleoptera between 1924 and 1951 (listed in Ryan, et al. (1984) pp.80-83.) Most appeared in the EMM, and many introduced new national and county records. In 1929 he prepared a supplementary list of Irish beetles which was published under the editorship of Dr R.Lloyd Praeger in Proc. R. Irish Academy, 93(B), pp.22-36 O’Mahoney’s collection of Irish Coleoptera amounting to 12,209 species was presented to the HDO by his family in 1951. Smith (1986) p. 84 notes that there is also manuscript material there including a notebook titled ‘Records of beetles in Co.Dublin (North East)’ and some correspondence. There is an obituary in INJ., 10, 1952, pp.229-230. (MD 7/04)