On the nomenclature of Bombus flavifrons Smith, 1866 (Hymenoptera, Apidae, Bombini)

The name Bombus flavifrons has been applied to two different bumble bee species in North America, one described by Ezra Cresson in 1863, the other by Frederick Smith in 1866. Bombus flavifrons Cresson, 1863 is currently considered the valid name for a common and widespread species in western North America, while B. flavifrons Smith, 1866 is considered a junior homonym of B. flavifrons Cresson, and thus not available. Consequently, B. columbicus Dalla Torre, 1890 was offered as a replacement name for B. flavifrons Smith. Smith’s taxon was described from a now-lost type specimen taken on Vancouver Island, British Columbia, Canada but has been considered a junior synonym of B. vosnesenskii Radoszkowski, 1862 since 1888. Prior to 2012 no other records of B. vosnesenskii were known from Vancouver Island, and it was considered very rare in Canada up until the early 2000s, known only from a few specimens from the southcentral mainland of British Columbia adjacent to the United States border. Bombus caliginosus (Frison, 1927) was not recorded in the literature from Canada until 2014 and is known only from five specimens collected in the 1970s at Victoria, Vancouver Island. Bombus caliginosus is distinguishable from B. vosnesenskii with some difficulty. Due to the morphological similarity of B. vosnesenskii and B. caliginosus , and their historical scarcity and disjunct distributions in Canada, we propose that B. flavifrons Smith is conspecific with B. caliginosus , a species that was not described until almost 40 years after the synonymy of B. flavifrons Smith under B. vosnesenskii . As the type specimen of Smith’s taxon is seemingly lost, we also designate a neotype of B. flavifrons Smith from Vancouver Island to support the proposed nomenclature. Though Bombus columbicus is here considered a senior synonym of B. caliginosus syn. nov. , under Article 23.9.1 of the ICZN Code, we designate the name nomen oblitum to maintain the prevailing use of B. caliginosus for this taxon.