We describe for the first time the biology and immature stages (egg, mature larva, and pupa) of the cleptoparasitic bee Radoszkowskiana rufiventris (Spinola) based on fieldwork in Egypt over a 2-year period. The biological information includes egg deposition and hatching, developmental rates, method of killing the host immature, larval feeding, larval defecation, cocoon spinning, and voltinism. We also describe the immature stages and some aspects of the biology of the following: (1) Megachile (Pseudomegachile) nigripes (Spinola), the host of R. rufiventris; (2) Coelioxys (Liothyrapis) decipiens Spinola, another cleptoparasite of M. nigripes; and (3) C. (Allocoelioxys) coturnix Pérez, which attacks the nests of M. (Eutricharaea) minutissima Radoszkowski from the same geographic region.

On the basis of the information gained from this study and from a review of pertinent literature, we consider whether Radoszkowskiana and Coelioxys shared a common cleptoparasitic ancestor or whether cleptoparasitism evolved independently in each.