Nesting Biology of Megachile (Chrysosarus) jenseni (Hymenoptera: Megachilidae) in Two Contrasting Pampean Agroecosystems: A Potential Pollinator for Alfalfa?

Abstract

Severalcrops depend on both managed and wild bees to produce fruits and/or seeds, andthe efficiency of numerous wild bees is higher than that of some managedspecies. Therefore,knowing and understanding the required resources for wild bees could enabledthe establishment of management practices to increase their populations. Here,we provide information about the nesting biology of Megachile (Chrysosarus)jenseni, a Faboideae-specialist bee species. Based on observations from twopopulations occurring in contrasting agroecosystems, this bivoltine speciesshowed common behavioral features shared with other species of subgenusChrysosarus, such as the use of petal pieces and mud as nesting materials andthe utilization of pre-existing cavities. Both studied populations showed abivoltine life cycle with a rapid early-summer generation and a secondgeneration, with most individuals overwintering. Main causes of mortality wereunknown diseases (or other factors), causing the death of preimaginal stages.Moreover, this species was attacked by a cleptoparasite megachilid (Coelioxysremissa), a parasitic eulophid wasp (Melittobia sp.), and a bee fly (Anthraxoedipus). Finally, we discussed the potential use of this leaf-cutter beespecies for alfalfa pollination.