The present contribution to the knowledge of the use of snail shells for nesting by Hymenoptera in southern Africa adds considerably to the earlier contribution by the authors on this subject. It establishes that the strategy of nesting in sand-filled shells is commonly employed by Quartinia Ed. André (Vespidae: Masarinae) throughout the sandy winter rainfall areas. It records additional rearings from Quartinia nests of Allocoelia Mocsary (Chrysididae), Tricholabiodes Radoszkowski and an undescribed genus (Mutillidae), and Apolysis hesseana Evenhuis and Greathead (Bombyliidae). Nesting by Tachysphex hermia Arnold (Crabronidae: Larrinae) in a sandfilled snail shell is recorded for the first time. It establishes that the distribution of use of snail shells for nesting by bees coincides with and extends along the south coast east of that of Quartinia. The bees (Megachilidae: Megachilinae) involved are osmiines, species of Wainia (Caposmia) Peters and Hoplitis (Anthocopa) Lepeletier and Serville, and anthidiines, including Afranthidium (Afranthidium) hamaticauda Pasteels, all cavity nesters using empty snail shells. The only other aculeate recorded as using empty shells is Alastor ricae Giordani Soika (Vespidae: Eumeninae). Parasitism in bee nests in snail shells is uncommon. Only Chrysis Linnaeus (Chrysididae) and Eupelminae (Chalcidoidea: Eupelmidae) were found, each at only two sites. The preferred snail shells are those of several species of Trigonephrus Pilsbry (Dorcasiidae) on the west coast and in the desertic areas and of Tropidophora ligata (Miiller) (Pomatiidae) along the south coast to the east, all indigenous species. In some areas the habitats of these have been invaded by an exotic snail, Theba pisana (Miiller) (Helicidae). Shells of this snail are used to a limited extent by the smaller nesters in snail shells. This exotic snail presents a threat to the indigenous snails and to the snail shell nesters. In some areas ongoing coastal development is also a threat.