The knowledge of the distributions, ecology and natural history of the pollen wasps (Vespidae: Masarinae) of the world has been reviewed (Gess, 1996). For the semi-arid to arid areas of southern Africa, the area with the highest species diversity of pollen wasps, the present contribution presents updated distributions of the genera and examines these in relation to the requirements for successful nesting. It shows that: the widespread, ground nesting genus Ceramius Latreille and the recently discovered Namibian ground nesting genus Priscomasaris Gess, the basal member of the Masarini, both of which require water and stable soil with a relatively high clay element for nesting, do not penetrate the true desert; the ground nesting genus Masarina Richards, with a southwestern distribution, has water dependant species but also, at least, one species which uses nectar instead of water, and, at least, one species which penetrates the desert in southern Namibia; the closely related widespread genus Jugurtia de Saussure, of which many species require water and stable soil with a relatively high clay element, may also have species which use nectar instead of water as there are two species which penetrate the desert, one in the south and one in the north of Namibia; the widespread genus Celonites Latreille, with species nesting in or above the ground on plants or stones and using nectar as a bonding agent, penetrates the desert along drainage channels; and the widespread, ground nesting genus Quartinia Ed. André, the most species diverse and smallest in size has many species which are truly successful desert dwellers. It is suggested that the reasons for the success of Quartinia species as desert dwellers are that: their small size enables them to reproduce successfully with minimal resources of provision; their remarkable ability as adults to produce self generated silk frees them from dependence on water or nectar as bonding agents in nest construction and enables them to nest in sand in nature such that it cannot be cemented with water or nectar; in windswept areas they are able to nest in small pockets of stable sand such as that trapped in snail shells; they are able to fly and forage in gale force winds; and they are able to fly at extremes of temperature, both high and low.