Meet the mustache wasps: phylogenetics and nesting behavior of Crabronini (Hymenoptera: Crabronidae)

Crabronini are well-known, not only for their narrow, shiny, silver-setaed clypeus (or mustache), but also for their highly diverse predatory and nesting proclivities. Yet a good understanding of the evolution of such behaviors has been limited by the absence of basic biological information for a number of genera and by a lack of modern cladistic analyses of this tribe. This state of affairs is partially remedied by a recently derived phylogeny of Crabronini based on adult external and internal morphology. This phylogeny is herein presented, classificatory changes are proposed, and nesting behavior is considered. In this new light, the early evolution of the group is shown to be characterized exclusively by ground-nesting habits. Nesting in plant materials of various kinds is derived well within the subtribe Crabronina and may have spawned a radiation of taxa. Reversals to ground-nesting habits have occurred repeatedly.