During the course of research on the wasps and bees of semi-arid areas, Sarah and Fred Gess, two eminent entomologists, observed that what appears at first glance to be the bottom of a C. royenii flower is in fact tightly appressed, hairy staminal filaments curving inwards from the cup walls at 5 mm above the true bottom of the flower. Above this level, the filaments separate and rise upwards and outwards to hold the anthers erect. The flowers are most often visited by a black carpenter bee with rufous legs- Xylocopa lugubris (Apidae: Anthophorinae) and two species of pollen wasps (Vespidae: Masarinae).
The robust carpenter bee flies straight into the flowers with its underside towards the centre of the flower. In doing so it makes contact with the anthers when in the pollen presenting phase, and with the stigmas when in the receptive phase-the perfect pollinator for these flowers. Xylocopa lugubris , which nests in dry, pithy stems, usually of Aloe inflorescences, is widespread in Africa and is therefore available throughout the range of C. royenii.
Unlike the carpenter bee, the two relatively small pollen wasps are not very reliable pollinators as they often drink nectar from a flower without making contact with the anthers or stigmas. The wasps were observed using the flowers of C . royenii also as a shelter for sunning themselves, especially during cool, breezy weather, as well as for courting and mating!
Distribution and Habitat
Codon royenii occurs in semi-desert and desert parts of Namibia, Northern and the Western Cape. The core distribution area of C. royenii coincides with the winter rainfall Succulent Karoo Region (Van Wyk & Smith 2001), with short extensions into adjacent parts of Namibia and the Northern Cape, areas that receive mainly summer or all-season rainfall. It inhabits sandy flats, dry, sandy river beds, rocky slopes, pockets of gravel between boulders, disturbed places or also occurs along roadsides.
Uses and cultural aspects
Because of its copious nectar (which explains its common name, honey bush), the flowers of Codon royenii are collected by the Nama people as a delicacy (Gess 1999). The predominantly spiny habit may protect the plants against browsing by animals in the very dry areas of southern Africa where they occur. Plants of C. royenii are nonetheless eaten by stock when the plants are young.