Ludwig Mally, a pharmacist who resided in Cape Town for most of his adult life, was registered as a chemist and druggist in the Cape Colony on 6 March 1867 (not in September 1858 as listed in the Government Gazette of 9 January 1885). When the Cape Pharmaceutical Society was formed in January 1887 he served as a member of its first executive committee. By that time he and Johan Carl Adolf Geister were the proprietors of the firm Wentzel and Schleswig, wholesale chemists and druggists, on the corner of Adderley and Shortmarket Street. In 1890 he was one of a committee of four pharmacists who considered amendments to a draft of what became the 1891 Medical, Dental and Pharmacy Act. Their most important (and successful) recommendation was that a separate Pharmacy Board be created.
In 1897 Mally accompanied Rudolph and Max Schlechter* on a zoological collecting trip, by ox-wagon, from Piquetberg to the Orange River. The specimens that he and Rudolph Schlechter collected were donated to the South African Museum. Mally's contribution consisted of some 34 specimens representing four species of scorpions from the Clanwilliam district and Namaqualand. The next year he donated a collection of spiders to the museum.
Mally became a member of the South African Philosophical Society in either 1897 or 1894. His membership ceased when it became the Royal Society of South Africa in 1908. By 1903 he was an associate member, and by 1906 a full member, of the South Africal Association for the Advancement of Science.