Examination of Hivetop Incubator Efficacy for Emerging Osmia lignaria (Hymenoptera: Megachilidae) and the Impact on Apis mellifera (Hymenoptera: Apidae) Colonies

Osmia lignaria Say is used in combination with Apis mellifera L. to pollinate U.S. orchard crops. The deployment of O. lignaria requires artificial warming to synchronize adult bee emergence with crop bloom. However, current methods for emerging bees are time consuming and inefficient; the Hivetop Incubator (HTI) invention creates a space atop an A. mellifera hive whose heat flows through the screened bottom of the HTI to incubate cocooned O. lignaria adults therein. In response to HTI heat, O. lignaria adults chew out of cocoons, find an exit hole, and fly away to nest in provided nesting sites and, thereby, pollinate a crop. Objectives for studies performed in Utah and Washington were to: 1) determine whether HTIs inhibit A. mellifera thermoregulation or colony growth, 2) compare O. lignaria emergence duration from an HTI with and without hive heat, and 3) assess whether O. lignaria females leave HTIs located at the orchard edge to nest throughout the orchard. We found no significant differences between the internal temperatures of A. mellifera colonies with and without HTIs and no impact on A. mellifera food storage or brood production. Osmia lignaria in hive-heated HTIs emerged 3× faster than bees in unheated HTIs. Heated HTIs were significantly cooler than hive temperatures but significantly warmer than HTIs atop empty hive boxes. Osmia lignaria nest distribution was not correlated to the location of HTIs at the orchard edge. Overall, HTIs were effective for timely, on-site emergence of O. lignaria for orchard pollination without negatively impacting A. mellifera colonies.