Nesting behaviour and provisioning in Bembix merceti and Bembix zonata (Hymenoptera: Crabronidae)

We studied the nesting behaviour and provisioning of Bembix merceti Parker and Bembix zonata Klug during three flight seasons (1993-1995). The females of B. merceti capture Diptera from seven different families to feed their larvae. Provisioning is progressive. The females provide a greater number of prey over subsequent days during larval growth. This activity begins increasingly earlier and lasts for longer, and prey capture is increasingly faster. Although the activity of the females is greater during the middle hours of the day, towards the end of each day the number of prey per wasp increases slightly and the duration of provisioning flights is reduced. Regarding Bembix merceti , we also report on nest structure and excavation as well as about the different natural enemies of these wasps. The data recorded for B. zonata refer to nest digging and structure, the wasps' natural enemies and their provisioning strategies, which in general are similar to those seen for the females of B. merceti .