Lost type specimen rewrites the history of a rare Vancouver Island bumble bee

Sometimes the biggest revelations in science come not from new discoveries in the field, but from old specimens in museum drawers and the tangled history of names attached to them. A new study published in the Journal of Hymenoptera Research has untangled a 160-year-old nomenclatural mystery surrounding a North American bumble bee, revealing that a name long considered invalid actually belongs to a species so rare in Canada that it is known from just five specimens collected in the 1970s. The work, led by Cory Sheffield and Paul Williams, demonstrates how careful analysis of historical distributions, type specimens, and the rules of zoological nomenclature can reshape our understanding of biodiversity itself.

The story begins with two entomologists who, unknowingly, gave the same name to two different bumble bees. In 1863, Ezra Cresson described Bombus flavifrons, the yellow-fronted bumble bee, a common and widespread species of western North America that ranges well into the western Arctic and as far east as the Hudson’s Bay region of Ontario. Three years later, Frederick Smith, writing in the appendix to J.K. Lord’s naturalist account of British Columbia, used the very same name for a different yellow-faced species. Smith’s specimen had been collected on Vancouver Island sometime between 1858 and 1862, during Lord’s stationing there, and it was the only new bee species described in that work. Because Cresson’s name came first, Smith’s taxon was considered a junior homonym and thus unavailable under the International Code of Zoological Nomenclature.

To complicate matters further, Smith’s type specimen, taken on Vancouver Island, British Columbia, is now seemingly lost. In 1888, Anton Handlirsch synonymized Smith’s taxon under Bombus vosnesenskii, a species described by Radoszkowski in 1862 and now commonly called the yellow-faced bumble bee. This synonymy stood for well over a century, and in 1890 Dalla Torre proposed Bombus columbicus as a replacement name for Smith’s unavailable taxon. But the new research argues that this synonymy was, in all likelihood, incorrect from the start.

The key insight comes from the historical distribution of the species involved in Canada. Prior to 2012, no records of Bombus vosnesenskii were known from Vancouver Island at all. The species was considered very rare in Canada up until the early 2000s, known only from a few specimens collected in the southcentral mainland of British Columbia adjacent to the United States border. In fact, only Buckell in 1951 provided specific locality information for the species in Canada, recording just three specimens from Osoyoos from 1925. Since then, Bombus vosnesenskii has undergone rapid range expansion and is now one of the most common bumble bees in southern parts of the province, extending onto Vancouver Island. This expansion may be due in part to the use of commercially available colonies in British Columbia, though natural spread from the adjacent United States may also be a contributing factor.

By contrast, Bombus caliginosus, a species not described until 1927, almost 40 years after Smith’s taxon was synonymized under Bombus vosnesenskii, is known in Canada only from southernmost Vancouver Island. These occurrences are based on five female specimens collected in the 1970s at Victoria, British Columbia, now held at the American Museum of Natural History. The species is also known from adjacent Stuart Island in the San Juan Islands and the Olympic Peninsula in Washington State. Given the morphological similarity between Bombus vosnesenskii and Bombus caliginosus, and their historical scarcity and disjunct distributions in Canada, the researchers propose that Smith’s taxon is actually conspecific with Bombus caliginosus, not with Bombus vosnesenskii.

The morphological evidence supporting this distinction is subtle but consistent. Females of Bombus caliginosus have a longer malar space, the distance between the mandibular hinges below the compound eye, with a length-to-width ratio of 0.90 compared to 0.71 in Bombus vosnesenskii. In many specimens of Bombus caliginosus, the fourth sternum bears a weak apical band of pale hairs, at least laterally, though this character is also present in some specimens of Bombus vosnesenskii. Tergum 4 of Bombus caliginosus often has some dark hairs basally, especially medially, while in Bombus vosnesenskii the black hairs are lacking or few. Stephen noted in 1957 that the relative lengths of the first and third flagellomeres also differed, with the first longer than the third in Bombus caliginosus but subequal in Bombus vosnesenskii. Williams and colleagues additionally noted differences in the size of punctures on the apical margin of the clypeus, being small in Bombus caliginosus but large in Bombus vosnesenskii.

Males of the two species can also be distinguished by the relative lengths of flagellomeres one and three, which are subequal in Bombus caliginosus but with the first shorter than the third in Bombus vosnesenskii. The males also differ in the shape of the apical recurved portion of the penis-valve head, narrowing apically in Bombus vosnesenskii but remaining subparallel in Bombus caliginosus. Thorp and colleagues provided illustrations noting differences in the shapes of the seventh and eighth sterna, the latter gradually narrowing apically in Bombus caliginosus while widely truncate apically in Bombus vosnesenskii. Despite these characters, all three major taxonomic treatments have stressed the difficulty of distinguishing the two species, especially for females.

Because Smith’s type specimen is lost, the researchers designated a neotype from Vancouver Island to fix the name to a physical specimen. The neotype is a female worker collected at Butchart Gardens in Victoria on 30 May 1973 by S. Gittelman, held at the American Museum of Natural History. The original description of Smith’s taxon was of a female with a body length of approximately 18 millimetres, consistent with the neotype selected. With this designation, Bombus columbicus is considered a senior synonym of Bombus caliginosus. However, under Article 23.9.1 of the Code, the prevailing usage must be maintained if the senior synonym has not been used as a valid name after 1899, which is the case here. The name Bombus caliginosus has subsequently appeared in numerous taxonomic, faunistic, and ecological papers, so the conditions for maintaining prevailing usage are met. Accordingly, Bombus columbicus is designated a nomen oblitum, a forgotten name, while Bombus caliginosus is designated the nomen protectum, the protected name.

The research also highlights the challenges of identifying these morphologically similar species in the era of citizen science. Online platforms such as Bumble Bee Watch and iNaturalist typically offer excellent occurrence documentation for bumble bees, but these two species are similar enough on a macro scale that identification from colour patterns shown in photographs is likely not reliable, as there are no consistent differences. Identification may only be possible when images show the malar space length or the ventral surface of the metasoma. Males of the two species are even harder to reliably identify from photos. Though all 400-plus specimens examined from British Columbia for this study have been identified as Bombus vosnesenskii, continued surveys and collection of specimens will be required to confirm the presence of Bombus caliginosus in, or its extirpation from, Canada.

This study exemplifies how modern taxonomy serves as a bridge between historical collections and contemporary biodiversity understanding. By carefully mining taxonomic, faunistic, and ecological literature, examining type material and photos of types, and analyzing over 400 specimens held at the Royal Saskatchewan Museum and Royal British Columbia Museum, the researchers have resolved a nomenclatural puzzle that has persisted since the Victorian era. The work also underscores the importance of museum collections in documenting biodiversity change over time, and the value of the International Code of Zoological Nomenclature in providing a stable framework for naming species. As bumble bees face mounting pressures from climate change, habitat loss, and disease, understanding the true identity and historical distributions of even the rarest species becomes ever more critical for conservation planning.

Subject of Research: Taxonomic nomenclature and type designation of the bumble bee species Bombus flavifrons Smith, 1866

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

Article References: Sheffield, C. S., Heron, J. M., & Williams, P. H. (2025). On the nomenclature of Bombus flavifrons Smith, 1866 (Hymenoptera, Apidae, Bombini). Journal of Hymenoptera Research, 98, 861-870. https://doi.org/10.3897/jhr.98.163217

Image Credits: AI Generated

DOI: 10.3897/jhr.98.163217

Keywords: bumble bees, taxonomy, nomenclature, neotype, Bombus caliginosus, Bombus vosnesenskii, Vancouver Island, ICZN Code, Journal of Hymenoptera Research, Bombus, flavifrons, Smith