Abstract
In 1979, C. D. Michener proposed a hypothesis for the evolutionary history of the large, cosmopolitan, cleptoparasitic bee genus Nomada. This hypothesis was based on known host relationships and the geographic distribution of extant species. One clear-cut prediction was that a cladistic analysis should show that the Neotropical species of Nomada parasitic upon exomolapsine anthophorid bees occupy the most basal position on a cladogram of subgroups within Nomada. This paper presents the results of such a cladistic analysis, which did not confirm Michener's prediction. The implications of the cladistic analysis for an interpretation of the phylogenetic history of Nomada are discussed, and known host associations for the genus worldwide are tabulated. No simple global evolutionary scenario is suggested by the cladistic analysis. The genus Nomada may be very old, and its constituent groups may have been involved in the complex histories of the biota of several continents.

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