The Lepidoptera section at the museum houses the most comprehensive collection of butterflies and moths from southern Africa in the World, consisting of more than one million specimens stored in excess of 7,000 drawers, reflecting the results of more than a century of collecting and research. From early on, the original focus on the then Transvaal extended first across South Africa and then the subregion, and today there exist comprehensive holdings especially from Namibia, Zimbabwe and Swaziland, with Botswana, southern Mozambique and Lesotho still being somewhat under-represented.
As mentioned above, the original mandate of the collection was to document the Lepidoptera fauna of the then Transvaal Republic. This quickly expanded as a result of the annexation of the Transvaal by the British, and the result of meeting these new challenges is reflected in the steadily growing number of species recorded from southern Africa: the first checklist, which appeared in 1917, listed 3607 species; and the latest inventory, published in 2002, listed no fewer than 8497 species and subspecies out of a total of perhaps 12,000 to 15,000.
Although generally representative, a particular feature of the collection is the strong representation of the so-called microlepidoptera, a group that tends to be under-represented in many collections because of the difficulties associated with their study. This is to a large extent due to the efforts of Dr A.J.T. Janse (1877-1970), whose extensive private collection of southern African moths was purchased by the Government in 1945 and subsequently amalgamated with the existing Lepidoptera collection at the museum. In addition to working on several groups of microlepidoptera himself, Janse assiduously sent specimens to England for identification and description by E. Meyrick (1854-1938), the acknowledged World authority at the time. Research on microlepidoptera was continued by Dr L. Vári, who joined the then Transvaal Museum in 1948; he mainly focused on various groups of leafminers in addition to being a prodiguous fieldworker.
Another name firmly linked to the Lepidoptera collection is that of Dr G. van Son (1898- 1967). Upon his joining the staff of the then Transvaal Museum in 1924 van Son was expected to focus his attention on several groups of insects but quickly specialized on butterflies and skippers, and his most lasting legacy is undoubtedly the series of four monographs entitled The Butterflies of Southern Africa, published between 1949 and 1979, the fourth volume having been edited posthumously by Dr L. Vári.
With the appointment of the current incumbent, Dr M. Krüger, in 1991, the focus of taxonomic and systematic research switched to various groups of the so-called macrolepidoptera, including ennomine geometrids, noctuids, and lithosiine arctiids.