Hoverflies (Diptera: Syrphidae) are agriculturally important organisms because they can offer dual ecosystem services: adults can pollinate, and larvae (of some species) can predate on pests (Doyle et al. Reference Doyle, Hawkes, Massy, Powney, Menz and Wotton2020; Dunn et al. Reference Dunn, Lequerica, Reid and Latty2020; Pekas et al. Reference Pekas, De Craecker, Boonen, Wäckers and Moerkens2020; Rodríguez-Gasol et al. Reference Rodríguez-Gasol, Alins, Veronesi and Wratten2020). Hoverflies have also been used as bioindicators in Europe because different functional groups, primarily determined by larval feeding habitat, have been found to vary with vegetation (Sommaggio Reference Sommaggio1999; Speight et al. Reference Speight, Monteil, Castella and Sarthou2010). Despite the insects’ importance, the literature on hoverflies in Alberta is almost entirely limited to taxonomic papers (e.g., Curran Reference Curran1923; Vockeroth Reference Vockeroth1992; Young et al. Reference Young, Marshall and Skevington2016; but see Borkent and Harder Reference Borkent and Harder2007) and Harper’s (Reference Harper1959, Reference Harper1963, Reference Harper1978) aphid control studies. Here, new records of hoverfly species in Alberta are presented, including one species that has not been previously collected in Alberta, two species that are of conservation concern, and two species that have fewer than 15 records across their entire range. Furthermore, the presence of one species that has previously been found only in the Rocky Mountains and not in agricultural areas and of three species that to date have been found in Alberta only through research-grade iNaturalist observations is confirmed.
The overarching goal of the present study was to examine the relationship between hoverflies and agricultural field borders in central Alberta in order to inform agricultural and conservation management plans (Pizante et al. Reference Pizante, Acorn, Jiménez and Frost2025). Twenty Malaise traps (NHBS black and white Malaise trap; NHBS, Totnes, Devon, United Kingdom) were placed within 1 m of, and with the openings running parallel to, 10 canola crops in central Alberta, Canada (Fig. 1). Propylene glycol (100%) was used as a preservative in the collection heads. The contents of the Malaise traps were collected every two weeks from 17 May to 20 August 2021. Collected hoverflies were sorted under dissecting microscopes, pinned, and identified to genus, using Vockeroth and Thompson (Reference Vockeroth, Thompson, McAlpine, Peterson, Shewell, Teskey, Vockeroth and Wood1987) or Miranda et al. (Reference Miranda, Young, Locke, Marshall, Skevington and Thompson2013). Keys to identify specimens to species included Shannon (Reference Shannon1916), Vockeroth (Reference Vockeroth1992), and Young et al. (Reference Young, Marshall and Skevington2016). Skevington and Locke (Reference Skevington and Locke2019) and BugGuide (https://bugguide.net) were used as additional aids for all identifications. Identifications of our Platycheirus specimens were confirmed by Dr. Andrew D. Young (University of Guelph, Guelph, Ontario, Canada). Vouchers were deposited in the E.H. Strickland Entomological Museum (UASM), Edmonton, Alberta, Canada (accession numbers: 423878, 423879, 423901, 423912, 423950, 423968, 423970, 423976, 423981, and 423985).
Figure 1. Map of study sites and locations of new Alberta hoverfly records with reference to the City of Edmonton, Alberta, Canada: A, locations where new records of species were found – although three individuals of Platycheirus varipes were found, two specimens of P. varipes were found at the same site (southernmost green point in A); B, locations where species of conservation concern were found; and C, locations where species with limited records were found. Edmonton shapefile available to the public from the City of Edmonton (2019). Canada shapefile available to the public from the Government of Canada (2016). Map created in QGIS (https://www.qgis.org).
The following literature, collections, and databases were used to confirm the records: Strickland (Reference Strickland1938, Reference Strickland1946), Vockeroth (Reference Vockeroth1992), Amos (Reference Amos2019), Skevington and Locke (Reference Skevington and Locke2019), the Alberta Conservation Information Management System (ACIMS) database of Alberta flies (Government of Alberta 2022), the Global Information Facility (GBIF), the Canadian National Collection of Insects, Arachnids and Nematodes (CNC; Ottawa, Ontario, Canada), the Royal Alberta Museum (PMAE; Edmonton), the Northern Forestry Centre, Canadian Forest Service, Natural Resources Canada (NFC; Edmonton), and John H. Acorn collection (JHAC; Edmonton). In the GBIF searches, “human observation” was included as an acceptable basis of record to check research-grade iNaturalist observations and specimens preserved in museums or collected as a part of the International Barcode of Life Consortium.
One species was found that has not been recorded in Alberta before the present study. Three specimens of Platycheirus varipes Curran were collected on 11 June, 10 August, and 16 August 2021 (Fig. 1A). In North America, this species has previously been collected in the Yukon, Northwest Territories, northern Manitoba, northern Ontario, Québec, and Prince Edward Island, Canada, in Alaska, Wyoming, and Maine, United States of America, and in Greenland (Young et al. Reference Young, Marshall and Skevington2016; Skevington and Locke Reference Skevington and Locke2019). Outside of North America, this species has also been collected in Norway, Sweden, Finland, and Russia (GBIF 2024a).
Two species of conservation concern were found during the present study. Eristalis brousii Williston is extirpated throughout most of its range, possibly through replacement by an introduced Palearctic species, E. arbustorum (Linnaeus) (Skevington and Locke Reference Skevington and Locke2019). Eristalis brousii is being considered for status assessment in Canada, which could make it the first hoverfly species to be listed under Canada’s Species at Risk Act (Committee on the Status of Endangered Wildlife in Canada 2024). It is still present in Alberta, as confirmed by seven records collected after 2000: one CNC record collected in 2004 from Elk Island National Park (CNC_Diptera9599), one PMAE record collected in 2010 near Wainwright, Alberta (PMAE.IZ00119388), and five JHAC records – one collected in 2017 at the Summer Village of Gull Lake, Alberta; one collected in 2016 near Empress, Alberta; one collected in 2015 at the University of Alberta’s Mattheis Research Ranch near Gem, Alberta; and two collected in 2013 on the west arm of Pakowki Lake. In this study, two specimens of E. brousii were collected on 3 June and 11 June (Fig. 1B). Furthermore, no individuals of E. arbustorum were found in this study, although three records of the species have been reported in the province, all from the JHAC: one collected in 2015 near Carrot Creek, Alberta, and two collected in 2013 on the west arm of Pakowki Lake.
One specimen of Parhelophilus brooksi Curran was found on 14 June (Fig. 1B). The last known record of P. brooksi is from 1980. Although too few records exist to make a formal status assessment, the species is conspicuous and easily identifiable, making it unlikely that the lack of records is due to insufficient collection or identification efforts (Klymko et al. Reference Klymko, Schlesinger, Skevington and Young2023). However, in 2021, the same year as the present study, two iNaturalist records appeared: one from Cariboo, British Columbia, Canada (Van Loon and Van Loon Reference Van Loon and Van Loon2021) and another from Peterborough County, Ontario (Yukich Reference Yukich2021).
Two species were found that are known in North America only from 11 and 14 records, respectively (Young et al. Reference Young, Marshall and Skevington2016). Three specimens of Platycheirus parmatus Rondani and one specimen of P. perpallidus Verrall were collected in this study (Fig. 1C). These species are not yet of conservation concern – in fact, Klymko et al. (Reference Klymko, Schlesinger, Skevington and Young2023) list P. parmatus as secure – but the lack of records makes these new records notable nonetheless. It is possible that more specimens of P. perpallidus were collected, but the females are indistinguishable from those of P. quadratus (Say), P. immarginatus (Zetterstedt), and P. neoperpallidus Young. Males of P. immarginatus were also collected during the present study.
One specimen of Megasyrphus laxus (Osten Sacken) was collected. This species is well-documented in the Rocky Mountains (Skevington and Locke Reference Skevington and Locke2019) but has only recently been photographed and collected in agricultural lowlands (PMAE record from 2021 in Parkland County, Alberta (PMAE.IZ00162101) and 10 iNaturalist observations; GBIF 2024b).
The presence of three species whose records prior to ours consisted entirely of research-grade iNaturalist records was confirmed. These species are Sphaerophoria novaeangliae Johnson (one specimen, two iNaturalist observations; GBIF 2024c), S. pyrrhina Bigot (one specimen, one iNaturalist observation; GBIF 2024d), and Volucella evecta Walker (five specimens, two iNaturalist observations; GBIF 2024e).
Acknowledgements
This research took place on Treaty 6 territory, traditional lands of First Nations and Métis people. We thank Michelle M. Locke and Jeffrey H. Skevington for their advice, Andrew D. Young for confirming our identifications, two anonymous reviewers for their helpful comments, and Pilar Jiménez, Jessica Lagroix, Olivia deBourcier, Brittany Wingert, Alia Rauf, Ash Davidson, Hannah Kastelic, Naomi Isaac, and Sydney Kennedy-Flynn for their work on the larger project. We also thank the landowners who let us sample on their fields. Data collection was financially supported by the Alberta Conservation Association (ACA; Award Number: 015-00-90-285). We also acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC). Nous remercions le Conseil de recherches en sciences naturelles et en génie du Canada (CRSNG) de son soutien. R.P. acknowledges three Alberta Graduate Excellence Scholarships (AGES).
Competing interests
The authors declare no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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