Nest architecture and use of floral oil in the oil-collecting South African solitary bee Rediviva intermixta (Cockerell) (Hymenoptera: Apoidea: Melittidae)

Abstract

Nest architecture, use of floral oil for brood cell lining and pollen collecting are described for the first time for the genus Rediviva, using the South African endemic oil-collecting solitary bee species Rediviva intermixta. The nest consists of a dead-end vertical tunnel with a single brood cell located at the end of each of several horizontally branching lateral tunnels. Brood cells are lined with a thin layer of waxy material, presumably derived from chemically modified floral oil. Rediviva intermixta is a pollen generalist but relies on a small number of host plant species for oil-collecting. Brood cells are provisioned with pollen from at least six plant families, but with a preference for non-oil-producing Scrophulariaceae. The nesting biology and Dufour’s gland size of the species are discussed and compared with the closely related genera Melitta and Redivivoides (non-oil-collecting) and Macropis (oil-collecting). The differences between Macropis and Rediviva suggest that oil-collecting in the two genera evolved independently.

Keywords:

• Rediviva
• solitary bee
• nesting biology
• oil-collecting
• floral host

Acknowledgements

Northern Cape Nature Conservation Service is gratefully acknowledged for giving their permission to collect bees and pollen samples. I am very much indebted to Kim Timmermann for the analysis of pollen samples and his help with nest excavations. Tonya Lander improved the quality of the manuscript by her insightful comments and linguistic corrections. I am indebted to Jerome G. Rozen, Jr. and two anonymous reviewers whose comments and questions contributed to the quality of this paper.