A distributional checklist of the sawflies (Hymenoptera) of Canada, Alaska (USA) and Greenland (Denmark) is presented. In total, 758 extant, described species, classified in 113 genera in 12 families are recorded. Of these, 729 (in 113 genera in 12 families) are reported from Canada, 183 (in 48 genera in 8 families) from Alaska, and 7 (in 1 genus) from Greenland. The list includes 69 new species records and 5 new generic records for Canada and 29 new species records and 7 new generic records for Alaska. The family Xiphydriidae is also newly recorded from Alaska. No new records are reported from Greenland. Eighty-four new combinations are proposed for species of Nematinae (Tenthredinidae). Distributions are listed for all species, for those in Canada by province or territory, except the province of Newfoundland and Labrador is divided into the island of Newfoundland and the region of Labrador. This inventory is compared with previous Nearctic and Palaearctic surveys, checklists and catalogues.

Northern North America, sawflies, species distributions

Sawflies (including horntails) comprise an ancient series of lineages in the order Hymenoptera. Including fossils, there are 8618 described species of sawflies in the world (Taeger et al. 2018) compared to a total of about 154,000 in the order Hymenoptera (Huber 2017). The earliest known fossils of Hymenoptera are sawflies of the family Xyelidae (Riek 1955; Lara et al. 2014) from the middle to late Triassic. Previously, sawflies were classified in the suborder Symphyta (Smith 1979a); however, morphology-based phylogenetic studies on the order Hymenoptera established that sawflies were part of a paraphyletic grade of lineages that diverged prior to the origin of the suborder Apocrita, a clade that includes all other extant families of Hymenoptera (Königsmann 1977; Rasnitsyn 1988; Ronquist et al. 1999). This hypothesis of relationships has been supported by more recent studies using molecular data, e.g., Heraty et al. 2011; Peters et al. 2017. In most of these studies, the sawfly superfamily Xyeloidea (family Xyelidae) is sister group to all other Hymenoptera (but see Peters et al. 2017) and superfamily Orussoidea (family Orussidae) is sister group to Apocrita. Sawflies are currently classified into seven extant superfamilies and fourteen extant families (Taeger et al. 2010, 2018). All extant superfamilies are present in northern North America with representatives of all families except for Blasticotomidae (Tenthredinoidea) and Megalodontesidae (Pamphilioidea) (Taeger et al. 2018; Bennett et al. 2019) (Table 1 and Figs 2–26).

In terms of biology, all sawflies are herbivorous as larvae, except for Orussoidea which are parasitoids of horntails (Hymenoptera: Siricidae) (Rawlings 1957) and wood-boring beetles (Coleoptera) (Powell and Turner 1975). Most larvae are external feeders on angiosperms, but some taxa feed externally on conifers, for example, Diprionidae (Benson 1939), Pamphiliidae (Middlekauff 1958) as well as some Tenthredinidae (e.g., Prous et al. 2017). A few taxa, mostly in the tenthredinid subfamily Selandriinae, feed externally on ferns (Smith 1969b). Feeding inside plants has evolved several times, for example, wood-boring in Anaxyelidae (Wickman 1967), Siricidae (Schiff et al. 2012) and Xiphydriidae (Smith 1976a). Some larvae develop internally in stems, especially stem sawflies (Cephidae) (Ries 1937), whereas others feed and develop inside reproductive organs of their host plants, e,g,, species of Xyela Dahlman (Xyelidae) in the staminate cones of pine trees (Pinus Linnaeus) (Burdick 1961). Some species, especially in the genus Euura Newman have larvae that are gall-makers (Benson 1960). In addition, some are leaf-miners, especially within the tenthredinid subfamily Heterarthrinae (Leppänen et al. 2012). Because of their herbivory, some species can be pests, e.g., the wheat stem sawfly, Cephus cinctus Norton (Cephidae) is a widespread pest of wheat and other cereals in North America (Shanower and Hoelmer 2004) and Sirex noctilio Fabricius (Siricidae), a recent invasive species in North America, is a major pest of pine trees in many parts of the world (Hoebeke et al. 2005). As adults, most sawflies, especially females, feed on pollen and nectar, but some taxa, especially in the tenthredinid subfamilies Allantinae, Selandriinae and Tenthredininae are active predators of other insects (Benson 1950) (Fig. 17).

On a world level, sawfly researchers are very well-served by the online Electronic World Catalog of Symphyta (ECatSym) (Taeger et al. 2018), which provides a comprehensive compilation of the taxonomic and distributional information and literature sources for all species of sawflies. With respect to surveys of sawflies within the Nearctic region, the catalogue of Smith (1979a) recorded 992 species in America North of Mexico and included distributional ranges for all species, including those known in Alaska and Greenland up to 1974. Masner et al. (1979) calculated the number of described species of sawflies by family in Canada (443). A comprehensive survey of the sawflies of the state of Alaska (USA) has not been made since Smith (1979a), whereas Vilhelmsen (2015) recently reviewed the sawflies of Greenland. Taxonomically, the Nearctic sawfly fauna is very well-studied relative to other groups of Hymenoptera (see references in Table 2), and on a regional level is probably better studied than any other part of the world except for Europe (see comparison in Results and Discussion). Historically, early workers provided catalogues of Nearctic sawflies, e.g., Edward Norton (1867, 1868). In the late 19^th and early 20^th centuries Alexander MacGillivray and, later, Sievert Rohwer both described over 500 species of sawflies (Taeger et al. 2010), the majority of which were Nearctic. In addition, Charles Marlatt revised the North American species of the taxonomically challenging tenthredinid subfamily Nematinae (Marlatt 1896). Starting in the 1930s Herbert Ross contributed to our knowledge of Nearctic sawflies, most importantly with his classification of the genera (Ross 1937) as well as his catalog of the sawflies of North America, north of Mexico (Ross 1951). More recently, from the 1960s to the present, David Smith revised many groups, described over 500 species and provided the catalogue of the sawflies of America North of Mexico (Smith 1979a). Goulet (1992) provided keys to the genera and subgenera of the sawflies of Canada and Alaska. It is the purpose of this paper to provide a distributional checklist of the sawflies of Canada, Alaska and Greenland, incorporating previously published, substantiated records as well as new records based on authoritatively identified specimens.

A total of 758 described, extant species of sawflies in 113 genera in 12 families are recorded in Canada, Alaska and Greenland (Tables 1, 2). This represents 8.2% of the 9250 species of Hymenoptera recorded from northern North America (Bennett 2021a). Of these, 729 species, in the same 113 genera and 12 families, are recorded from Canada. This is a 64.6% increase from the 443 species reported in Masner et al. (1979). Taeger et al. (2018) recorded 1245 extant described species in the Nearctic region, which means that northern North America has about 61% of the described Nearctic species, not taking into account new distributional records and species not included in Taeger et al. (2018).

Relative to other parts of the Northern Hemisphere, Canada’s sawfly fauna is less speciose and/or less well-known than other countries/regions. The land mass of Canada is 9.985 million km², which equates to one species per 13,697 km². Adding Alaska (1.718 million km²) and Greenland (2.166 million km²) to this calculation, the average species density of sawflies in northern North America is one species per 18,297 km². In contrast, Taeger et al. (2006) published a checklist of the sawflies of Europe, which recorded 1392 species of sawflies. Considering the land mass of Europe (10.18 million km²), this equals an average of one sawfly species per 7313 km². Other Northern Hemisphere sawfly surveys include Liston et al. (2014) for Britain and Ireland (539 species in 313,100 km² = one species per 580.9 km²), Naito et al. (2020) for Japan (875 species in 377,915 km² = one species per 431.9 km²) and Macek et al. (2020) for the Czech and Slovak Republics (750 species in 127,901 = one species per 170.5 km²). Because of the great differences in the geographic size of these three surveys compared to northern Northern America, it is difficult to make comparisons. A more appropriate comparison of sawfly species diversity between northern North America and a Palaearctic country is provided by Sundukov (2017) who recorded 1546 species in Russia (surface area 17.1 million km²), which equals an average of one sawfly species per 11,060 km². In summary, surveys of smaller areas generally have greater density of sawfly species recorded (except for northern North America compared to Russia), and there is a higher density of sawfly species recorded in all of the Palaearctic surveys compared to the northern Nearctic. The lower species richness of sawflies recorded from the northern Nearctic compared to the Palaearctic is likely an effect of lower sampling in the Nearctic. The western Palaearctic is certainly the best sampled region of the world for most groups of organisms, including sawflies. In conjunction with greater sampling, there has been more study of sawflies in Europe compared to northern North America, especially the hyperdiverse Nematinae. For example, Pristiphora Latreille has 221 described species (Taeger et al. 2018) of which about 120 are known from Europe (Prous et al. 2017). Haris (2006) treated the European species relatively recently and provided a key for 155 Palaearctic species, and Prous et al. (2017) revised 90 species from Scandinavia and neighbouring regions. In contrast, Pristiphora has only 55 described species in the entire Nearctic region (24.7 million km²) (Taeger et al. 2018) and has never been completely revised for the region, although unpublished work by H.R. Wong indicates that many undescribed Nearctic species exist and a revision of the genus for the region is currently in progress (S. Monckton, pers. comm.).

Figure 1. 

Map of Canada, Alaska and Greenland showing number of described, recorded sawfly species and percentage of total species for each region. Canada is comprised of all regions except for Alaska and Greenland. See Methods, Presentation of data section for acronyms of regions treated in the checklist.