Checklist of the apoid wasps (Hymenoptera, Apoidea excluding Anthophila) of Canada, Alaska and Greenland
Authors: Buck Matthias , Bennett Andrew M. R. 
Published: February 2025

The present checklist is the product of a critical taxonomic review of the Canadian/Alaskan fauna during the previous two decades. As of December 2024, 531 described species in 84 genera of apoid wasps (Ammoplanidae, Ampulicidae, Astatidae, Bembicidae, Crabronidae, Mellinidae, Pemphredonidae, Philanthidae, Psenidae, Sphecidae) are recorded from Canada and Alaska. Seventy species and two genera (Psammaletes Pate and Larra Fabricius) are newly recorded from the area, including eight accidentally introduced species and three naturally Holarctic species. Compared to the previous Catalog of Hymenoptera in America north of Mexico (Krombein 1979) the number of recorded species in Canada and Alaska has increased by 124% and the number of genera by 42%. The genera Foxia Ashmead and Pluto Pate are also recorded for the first time, but they are not included in the checklist because their species remain either unidentified or undescribed. A total of 23 species are non-native and have been introduced accidentally from other biogeographic regions. Crabro dietrichi R. Bohart is newly recognized as the only species endemic to the area of the checklist (restricted to Prince Edward Island, Canada). A total of 2109 provincial, territorial and Alaskan records are included, 705 of which (33.4%) are new. Records are based on verified material from 22 different collections, only 1.6% rely exclusively on data in the literature. The Alaskan fauna consists of 63 species (31 new records) in 24 genera (eight new records) and seven families, all of which are also known from Canada. No apoid wasps have been found in Greenland. The regions with the most diverse faunas are Alberta (326 species, 64 genera), Ontario (294 spp., 71 genera), British Columbia (292 spp., 64 genera) and Saskatchewan (248 spp., 58 genera). The highest number of new records are from Alberta (124 spp.), Saskatchewan (117 spp.), Manitoba (113 spp.) and New Brunswick (60 spp.). The greatest numbers of species exclusive to one political area within Canada and Alaska are recorded from British Columbia (63 spp.) and Ontario (44 spp.). In order to clarify species concepts, type material or images of types of 57 nominal species were examined. This led to 25 taxonomic changes. Eight synonyms are reinstated as valid species: Gorytes decorus Fox, sp. restit., Nysson freyigessneri Handlirsch, sp. restit., Lindenius errans (Fox), sp. restit., Oxybelus pacificus (Rohwer), sp. restit., Diodontus antennatus (Mickel), sp. restit. (extralimital to the area of the checklist), D. nigritus Fox, sp. restit. and Pemphredon bipartior Fox, sp. restit. Diodontus beulahensis (Rohwer), sp. restit. (extralimital to the area of the checklist) is a suspected synonym of D. americanus Packard. Fourteen new or revised synonymies are proposed: Crabro canningsi Finnamore, syn. nov. = C. maeklini Morawitz, Crossocerus eriogoni (Rohwer), syn. nov. = C. minimus (Packard), Solierella foxii (Viereck, 1906; nec 1902) (preoccupied), syn. rev. = S. mammillata Buck, nom. nov.; Diodontus gillettei Fox, syn. nov., D. rugosus Fox, syn. nov., D. florissantensis Rohwer, syn. rev., D. bidentatus Rohwer, syn. nov., D. siouxensis (Mickel), syn. nov., and D. striatus (Mickel), syn. nov. are all = D. americanus; D. vallicolae Rohwer, syn. nov., D. vallicolae salicis Rohwer, syn. rev., D. maestus (Mickel), syn. rev. and D. ater (Mickel), syn. rev. are all = D. nigritus Fox; Mimesa gregaria (Fox), syn. nov. = M. unicincta Cresson. Two new replacement names are proposed for preoccupied names: Solierella mammillata Buck, nom. nov. (for Niteliopsis foxii Viereck, 1906) and Mimesa curta Pulawski & Buck, nom. nov. (for Psen simplex Malloch, 1933). In an appendix, taxonomic changes and revised species concepts of 33 species or species complexes are briefly explained in order to clarify their status and avoid confusion. The biogeography of Canadian and Alaskan species is discussed, including Holarctic species and species shared with other biogeographic regions, distribution patterns within the Nearctic region, endemism, remarkable new records, geographic prevalence of nesting habits, distribution patterns and introduction timelines of introduced species, as well as faunal change. Diodontus minutus (Fabricius) is newly recognized as an introduced species from the Palearctic region despite first being discovered in North America in 1934. Based on literature data and observations on the internet platform iNaturalist.org, we document recent, rapid range expansions in ten native species of Sphecidae, Philanthidae and Bembicidae. These trends are likely caused by climate change and are projected to further increase apoid wasp diversity in Canada in the future. Lastly, we discuss the important contribution citizen science is making to faunistic wasp research through iNaturalist and other collaborative websites.