The genus Andrena in Belgium: revisions, clarifications, and a key for their identification (Hymenoptera: Andrenidae)

As an early-industrialising northern European country, Belgium has a comparatively wellstudied insect fauna. Despite this, many challenging insect groups have lacked domestic specialists, and so work is required to resolve outstanding issues for the Belgian fauna. The species-rich genus Andrena is no exception, being the largest bee genus in Belgium and more broadly the West Palearctic, and amongst its most taxonomically challenging. A critical review of the literature and examination of museum and contemporary collections has produced a list of 81 confirmed Andrena species for Belgium, with a further five species that cannot be positively confirmed as present historically. Nineteen species reported from or suggested as possibly present in Belgium are definitively excluded. The controversial taxon Andrena batava Pérez, 1902 is confirmed as present in Belgium along with Andrena apicata Smith, 1847, and its status is clarified through support from genetic and morphological evidence combined with a lectotype designation. A lectotype is also designated for Andrena mitis Schmiedeknecht, 1883. The controversial specific status of Andrena nigrospina Thomson, 1872 is supported by fresh genetic analysis as distinct from Andrena pilipes Fabricius, 1781, which is also confirmed as present in Belgium. Two members of the Andrena ovatula (Kirby, 1802) species complex are present in sympatry: A. ovatula and Andrena afzeliella (Kirby, 1802). An identification key to the genus is presented. These results illustrate the extent to which our understanding of this complex bee genus is incomplete, even in nominally better studied northern European countries.