Diptera of Canada.

The Canadian Diptera fauna is updated. Numbers of species currently known from Canada, total Barcode Index Numbers (BINs), and estimated numbers of undescribed or unrecorded species are provided for each family. An overview of recent changes in the systematics and Canadian faunistics of major groups is provided as well as some general information on biology and life history. A total of 116 families and 9620 described species of Canadian Diptera are reported, representing more than a 36% increase in species numbers since the last comparable assessment by JF McAlpine et al. (1979). Almost 30,000 BINs have so far been obtained from flies in Canada. Estimates of additional number of species remaining to be documented in the country range from 5200 to 20,400.

This paper is dedicated to the memory of Terry A Wheeler, an exceptional Canadian dipterist and long-time contributor to the Biological Survey of Canada, who passed away in the early stages of this project.

The world fauna of counts almost 160,000 named species (Borkent et al. 2018) divided into approximately 160 extant families (Pape and Thompson 2013). Flies dominate the Canadian insect fauna in numbers of named species and, in many habitats, in overall abundance. That dominance becomes especially apparent in the northern parts of the country where dipterans form a ubiquitous feature of the summer landscape.

occur in almost all freshwater and terrestrial habitats where they display an impressive range of life histories and feeding habits. From parasites to leafminers, predators and filter feeders (to mention only a few), flies have diversified to exploit almost all organic substrates for their development (see Courtney et al. (2017) and Marshall (2012) for detailed overviews). Canada holds approximately 20% of the world’s freshwater reserves so, unsurprisingly, families with aquatic stages are very well represented in the country. In the present survey, the (non-biting midges), whose immature stages are primarily aquatic, account for the most named species (798) in a single family (Table 1).

Table 1.

Census of in Canada.

Taxon1	No. species reported in McAlpine et al. (1979)	No. species2 currently known from Canada	No. BINs3 available for Canadian species	Est. no. undescribed or unrecorded species in Canada	General distribution by ecozone3A	Information sources
Nematocerous Diptera
Infraorder Tipulomorpha
Superfamily Tipuloidea
Tipulidae	5204	216	190	30	all ecozones	Oosterbroek 2018
Cylindrotomidae	? 4	7	6	0	Pacific Maritime, Boreal Plains, Boreal Shield, Newfoundland Boreal, Mixedwood Plains, Atlantic Maritime	Oosterbroek 2018
Limoniidae	? 4	354	345	186	all ecozones	Oosterbroek 2018
Pediciidae	? 4	56	52	0	all but Arctic	Oosterbroek 2018
Superfamily unassigned
Trichoceridae	20	21	34	10	all ecozones	Pratt 1992
Infraorder unassigned
Deuterophlebiidae	1	3	1	1	Boreal Cordillera, Montane Cordillera
Nymphomyiidae	2	1	1	0	Boreal Shield, Atlantic Maritime, Mixedwood Plains	Courtney 1994
Infraorder Psychodomorpha
Blephariceridae	11	7	4	3	all but Prairies
Psychodidae	30	34	114	10−50	all ecozones	Quate 1955, Young and Perkins 1984
Tanyderidae	2	2	0	1	Montane Cordillera, Atlantic Maritime
Infraorder Ptychopteromorpha
Ptychopteridae	7	8	5	8	all but Arctic	Fasbender and Courtney 2017
Infraorder Culicomorpha
Superfamily Chironomoidea
Chironomidae	480	798	4266	1000	all ecozones	Ashe and O’Connor 2009, 2012
Superfamily Simulioidea
Ceratopogonidae	180	263	1341	300	all ecozones	Borkent and Grogan 2009, Borkent 2016
Thaumaleidae	3	13	6	2−5	Pacific Maritime, Boreal Shield, Newfoundland Boreal, Montane Cordillera, Mixedwood Plains, Atlantic Maritime	Pivar et al. 2018
Simuliidae	110	164	153	20	all ecozones	Adler and Crosskey 2018
Superfamily Culicoidea
Dixidae	21	34	23	10	all ecozones
Corethrellidae	? 5	1	1	0	Mixedwood Plains	Borkent 2008, 2014
Chaoboridae	95	11	21	0	all ecozones	Borkent 1979, 1981, 2014
Culicidae	74	82	75	3	all ecozones	Thielman and Hunter 2007, Jackson et al. 2013, Giordano et al. 2015
Infraorder unassigned
Axymyiidae	1	1	1	2	Mixedwood Plains
Infraorder Bibionomorpha s. lat.
Anisopodidae	5	5	15	2−5	all but Arctic
Superfamily Scatopsoidea
Scatopsidae	30	30	48	15−20	all ecozones
Canthyloscelidae	16	1	1	0	all but Arctic
Infraorder Bibionomorpha s. str.
Pachyneuridae	1	1	1	0	Pacific Maritime
Bibionidae	407	26	29	2−3	all ecozones
Hesperinidae	?7	1	1	0	all Boreal ecozones	Papp 2010
Superfamily Sciaroidea
Ditomyiidae	?8	3	9	5−10	all but Arctic	Munroe 1974
Bolitophilidae	? 8	16	23	5	all ecozones	Bechev and Chandler 2011
Keroplatidae	? 8	28	95	4	all ecozones	Evenhuis 2006
Mycetophilidae	3508	489	1199	500	all ecozones
Cecidomyiidae	100	243	11,396	1000−16,000	all ecozones	Gagné and Jaschhof 2017
Diadocidiidae	? 8	2	8	5	all but Arctic	Bechev and Chandler 2011
Sciaridae	30	129	2863	100−200	all ecozones	Mohrig et al. 2013
Suborder Brachycera
Infraorder Xylophagomorpha
Superfamily Xylophagoidea
Xylophagidae	15	14	16	1−2	all but Arctic, Taiga Shield and Taiga Plains	Woodley 2011c
Infraorder Tabanomorpha
Superfamily Rhagionoidea
Rhagionidae	359	48	57	10−15	all ecozones	Kerr 2010
Bolbomyiidae	? 9	3	5	2	Pacific Maritime, Mixedwood Plains	Kerr 2010
Superfamily Tabanoidea
Pelecorhynchidae	4	5	1	1	Montane Cordillera, Mixedwood Plains
Oreoleptidae	0	1	2	0−1	Montane Cordillera, Boreal Cordillera	Zloty et al. 2005
Athericidae	3	2	3	0	all but Arctic and Prairies ecozones
Tabanidae	132	142	90	0	All but Arctic
Infraorder Stratiomyomorpha
Superfamily Stratiomyoidea
Xylomyidae	4	7	8	0	Pacific Maritime, Western Interior Basin, Boreal Shield, Mixedwood Plains, Atlantic Maritime	Woodley 2011a,b
Stratiomyidae	84	114	71	5−10	all but Arctic	Woodley 2001, 2011a
Infraorder unassigned
Acroceridae	20	20	14	5	all but Arctic
Nemestrinidae	2	2	0	0	Western Interior Basin
Infraorder Asilomorpha
Superfamily Asiloidea
Bombyliidae	7010	105	86	44	all ecozones
Mythicomyiidae	? 10	1	2	5	all but Arctic, Taiga Shield, and Taiga Plains	Evenhuis 2002
Hilarimorphidae	7	7	1	1	all but Arctic	Webb 1974, 1975
Asilidae	125	222	141	5−10	all but Arctic
Mydidae	2	2	1	0	Western Interior Basin, Mixedwood Plains
Apioceridae	1	1	0	0	Western Interior Basin
Scenopinidae	8	10	3	1−5	all but Arctic
Therevidae	30	50	28	0	all ecozones	Webb et al. 2013
Infraorder Eremoneura
Superfamily Empidoidea
Iteaphila group	?11	17	23	9	all ecozones
Oreogetonidae	? 11	7	8	1−2	all but Arctic
Empididae	30011,12	251	497	200	all ecozones
Brachystomatidae	? 11	11	11	2	all ecozones
Hybotidae	? 11	155	353	200	all ecozones
Dolichopodidae s.l.	50012	508	657	200	all ecozones	Pollet et al. 2004
Lower Cyclorrhapha
Lonchopteridae	4	7	6	0−1	all ecozones	Klymko and Marshall 2008
Superfamily Platypezoidea
Platypezidae	21	39	46	12	all ecozones
Superfamily Phoroidea
Phoridae	127	135	110	300	all ecozones
Superfamily Syrphidoidea
Syrphidae	500	539	359	34	all ecozones
Pipunculidae	45	85	170	170	all ecozones
Schizophora: Acalytratae
Superfamily Diopsidoidea
Diopsidae	1	2	2	0	Mixedwood Plains	Feijen 1989
Psilidae	25	27	28	3	all but Arctic
Strongylophthalmyiidae	1	2	2	0	Pacific Maritime, Prairies, Boreal Shield, Mixedwood Plains, Atlantic Maritime	Barber 2006
Tanypezidae	1	1	1	0	Boreal Shield, Mixedwood Plains	Lonsdale 2013
Superfamily Neroidea
Micropezidae	16	16	11	0	all ecozones	Merritt and Peterson 1976
Superfamily Sciomyzoidea
Sciomyzidae	85	120	143	15	all ecozones	Knutson et al. 1986
Sepsidae	17	19	27	5−10	all ecozones	Ozerov 2005
Conopidae	30	42	34	2−5	all but arctic ecozones
Coelopidae	4	4	3	0	Arctic, Pacific Maritime, Taiga Shield, Boreal Shield, Atlantic Maritime	Vockeroth 1965, Mathis and McAlpine 2011
Dryomyzidae	713	8	8	1−5	all but Arctic	Mathis and Sueyoshi 2011
Helcomyzidae	? 13	1	0	0	Pacific Maritime
Heterocheilidae	? 13	1	0	0	Pacific Maritime
Superfamily Lauxanoidea
Lauxaniidae	64	78	90	10	all ecozones
Chamaemyiidae	30	35	94	10	all ecozones
Superfamily Tephritidoidea
Tephritidae	40	122	82	21	all but Arctic	Foote et al. 1994
Platystomatidae	10	10	7	5	all but Arctic
Ulidiidae	3514	35	29	20	all but Arctic
Lonchaeidae	97	99	78	13	all but Arctic
Pyrgotidae	3	3	1	0	Pacific Maritime, Prairies, Mixedwood Plains
Richardiidae	0	1	0	0	Mixedwood Plains
Pallopteridae	9	9	7	9	all but Arctic
Piophilidae	31	31	35	4	all ecozones	Rochefort and Wheeler 2015
Superfamily Opomyzoidea
Agromyzidae	305	450	772	76	all ecozones
Clusiidae	6	22	22	0	all but Arctic	Caloren and Marshall 1998, Lonsdale and Marshall 2007
Asteiidae	5	5	8	3	all Boreal and Maritime ecozones, Montane Cordillera, Prairies, Mixedwood Plains
Anthomyzidae	4	37	33	3	all but Arctic	Roháček and Barber 2016
Periscelididae	2	3	8	5	all Boreal and Maritime ecozones, Montane Cordillera, Prairies, Mixedwood Plains	Mathis and Rung 2011
Odiniidae	5	6	8	3	all Boreal and Maritime ecozones, Montane Cordillera, Prairies, Mixedwood Plains	Gaimari and Mathis 2011
Opomyzidae	10	11	11	4	all ecozones	Wheeler et al. 1999
Aulacigastridae	3	2	3	1	all but Arctic	Rung and Mathis 2011
Superfamily Carnoidea
Chloropidae	100	140	361	260	all ecozones
Milichiidae	11	13	55	20−30	all ecozones	Brake 2009, Brochu and Wheeler 2009
Canacidae	515	10	11	0	all ecozones	Munari and Mathis 2010
Carnidae	8	12	21	5−10	all ecozones	Brake 2011, Stuke 2016
Acartophthalmidae	2	1	1	1	all but Arctic
Superfamily Ephydroidea
Drosophilidae	60	79	102	20−25	all ecozones	Brake and Bächli 2008, Miller et al. 2017, Bächli 2018
Ephydridae	150	197	182	10−15	all ecozones	Mathis and Zatwarnicki 1995
Curtonotidae	1	1	1	0	Prairies, Boreal Plains, Mixedwood Plains	Klymko and Marshall 2011
Diastatidae	5	7	11	2−3	all ecozones	Mathis and Barraclough 2011
Camillidae	1	2	1	0	Mixedwood Plains
Braulidae	1	1	0	0	Prairies
Superfamily Sphaeroceroidea
Sphaeroceridae	35	184	190	20	all ecozones	Roháček et al. 2001
Heleomyzidae	7416	72	74	38	all ecozones
Chyromyidae	5	5	10	5	Pacific Maritime, Prairies, Boreal Shield, Mixedwood Plains, Atlantic Maritime
Schizophora: Calyptratae
Superfamily Hippoboscoidea
Hippoboscidae	1317	17	1	0	all but Arctic	Graciolli et al. 2007
‘Muscoid grade’
Fanniidae	?18	84	85	8−10	all ecozones
Muscidae	52518	440	479	40	all ecozones
Anthomyiidae	375	515	412	10−30	all ecozones	Griffiths 1982–2004
Scathophagidae	130	126	115	29	all ecozones
Superfamily Oestroidea
Calliphoridae	40	62	39	0	all ecozones
Oestridae	15	17	7	0	all ecozones
Rhinophoridae	2	2	3	1	Boreal Shield, Newfoundland Boreal, Mixedwood Plains, Atlantic Maritimes	O’Hara et al. 2015
Sarcophagidae	85	135	132	5−15	all ecozones
Tachinidae	500	736	647	100	all ecozones	O’Hara and Wood 2004
Total	7056	9620	29,583	5205−20,458

1Higher classification follows a consensus of opinions of co-authors and collaborators; family limits follow Pape et al (2011). 2Numbers compiled from published records and collection holdings. 3Barcode Index Number as defined in Ratnasingham and Hebert (2013). 3ASee figure 1 in Langor (2019) for a map of ecozones. 4McAlpine et al. (1979) included , and in the .5McAlpine et al. (1979) included in . 6McAlpine et al. (1979) included this species in the which has since become a subfamily of the . 7McAlpine et al. (1979) included in . 8McAlpine et al. (1979) included , , and in the . 9McAlpine et al. (1979) included in . 10McAlpine et al. (1979) included in . 11McAlpine et al. (1979) included group, , and in . 12McAlpine et al. (1979) included the and in the . 13McAlpine et al. (1979) included the and in the . 14McAlpine et al. (1979) included these species under , now replaced by the senior valid name . 15McAlpine et al. (1979) included 4 species in the which has since become a subfamily of . 16McAlpine et al. (1979) included 4 species in the which has since become a subfamily of . 17McAlpine et al. (1979) included 1 species in the and 1 in the , both of which have since become subfamilies of . 18McAlpine et al. (1979) included in .

The diversity of flies in Canada was last reviewed by JF McAlpine et al. (1979) as part of a broader treatment of the terrestrial arthropods (Danks 1979). Subsequently, the three volumes of the Manual of Nearctic (JF McAlpine et al. 1981, 1987, JF McAlpine and Wood 1989) have been major catalysts for dipterological research in Canada and the USA. A detailed overview of these contributions, and the people who made them possible, was provided in Cumming et al. (2011). The identification keys to genus found in Volumes 1 and 2 (JF McAlpine et al. 1981, 1987) paved the way for future taxonomic work on the Nearctic fauna, and for many families they remain the best identification resource. While recent catalogues are now available for a number of Nearctic families, e.g., (Pollet et al. 2004) and (O’Hara and Wood 2004), no comprehensive catalogue has been published for the Canadian fauna of the whole order since Stone et al. (1965). The global online database, Systema Dipterorum (Pape and Thompson 2013), provides extensive information about names and literature; it is especially useful for resolving issues related to precedence and validity of names during taxonomic revisions.

As with many arthropod groups, the development of DNA-based identification and phylogenetic tools has had a strong impact on systematics. DNA barcoding using a part of the cytochrome c oxidase 1 (COI) gene (Hebert et al. 2003) has been applied to members of nearly all families found in Canada, and more specimens of flies have been DNA barcoded than of any other order in the country – 1.14M specimens as of June 2018 in the Barcode of Life Data System (BOLD; www.boldsystems.org). DNA barcoding and the Barcode Index Number (BIN) system (Ratnasingham and Hebert 2013) usually provide good estimates of species limits in taxa with good coverage, e.g., Canadian (Renaud et al. 2012b, Hebert et al. 2016) and (Rivera and Currie 2009). However, gaps and errors in existing barcode libraries in some freshwater taxa (Curry et al. 2018), as well as poor correspondence between COI DNA barcodes and morphology for at least one genus found in Canada ( Hough; Whitworth et al. 2007) warrant caution when using BINs alone as estimates of true species diversity. In any case, further investigations will be required to explore the great discrepancies between named species and BINs for some families such as the (243 vs 11,396) or the (129 vs 2863) (Table 1), and to determine the relative contributions of gaps in taxonomic knowledge and discordance with the DNA barcoding and/or BIN approach.

The Manual of Nearctic , especially Volume 3 (McAlpine and Wood 1989), also had a major impact on the field of phylogenetics. The hypotheses of family-level relationships and the proposed classification presented have served as a basis for future updates (Yeates and Wiegmann 2012) and have since been tested repeatedly using new sources of data and continuously evolving quantitative methods (see Wiegmann and Yeates (2017) for review). It is notable that while the last three decades have generated an impressive body of literature on phylogenetics, a lack of consensus still remains in many parts of the phylogeny (Borkent 2018). Consequently, the family concepts used in the present work follow Pape et al. (2011) but the classification reflects a consensus of opinions of co-authors and collaborators who have contributed data to this paper.

When compared to the data provided in JF McAlpine et al. (1979), the results of the present work (Table 1) show an increase from 101 to 116 families (excluding the unranked group formerly placed in ). While the and the represent new records for the country, most of the additional families represent reclassification of taxa formerly combined with other families (see text below and Table 1 for details). The numbers of recorded and named species have also increased since 1979 for most families, with the exception of those that were split (e.g., and ) or those in which numerous synonymies were uncovered (e.g., ). Especially worth noting are the and , with five- and nine-fold increases in species numbers since 1979, respectively. In each of these cases, the impressive increase in species numbers can be attributed to decades-long dedication to biosystematics study of particular families by individuals and institutions (S Marshall and colleagues at the University of Guelph, Ontario, for the and K Barber at the Great Lakes Forestry Centre in Sault Ste. Marie, Ontario, for the ).

JF McAlpine et al. (1979) compiled 7056 species of in Canada (mistakenly reported as 7058 in table 42) and estimated that an approximately equivalent number remained to be discovered. The 9620 species reported here represents a 36% increase since 1979. Significant advances have been made over the last four decades but some major gaps remain. While few families are known well enough to claim full coverage in Canada, the bulk of undescribed or unrecorded Canadian diversity is in the nematocerous families, especially those with diminutive and/or delicate adults such as the , , and , all of which are in great need of taxonomic attention (Table 1).

Nematocerous

The nematocerous (Lower ), previously known as , include those species of adult flies with elongate antennae composed of at least four flagellomeres. The group includes 36 extant families worldwide, of which 33 occur in Canada. The concepts and names of many families have changed since JF McAlpine et al. (1979) (see below and Table 1).

As adults, nematocerous tend to be long-legged and, compared to brachyceran , weaker fliers. Larvae are found in a wide array of habitats and include a large number of aquatic and semiaquatic taxa (see and below), fungal feeders, gall makers, detritus feeders, predators, and even parasites, among others. The biting flies are mostly in the and include those species that vector important diseases of humans, domestic animals and wildlife.

The nematocerous are clearly paraphyletic in relation to the , although the exact sister group of within the nematocerous is not certain (Woodley et al. 2009). The phylogenetic relationships among families have also been, in part, rather unstable. The phylogenetic analysis by Wood and Borkent (1989) laid groundwork, which was largely supported by Oosterbroek and Courtney (1995). Michelsen (1996) proposed the , a clade including , , , , , , , and based on characters of the adult prothorax and cervical sclerites. However, a study of the male internal reproductive system by Sinclair et al. (2007) did not support the and indicated instead that the + + + + formed a monophyletic assemblage.

Molecular analyses have proposed a wide array of differing relationships that conflict with each other, at least in part, and with most morphological analyses (Pawlowski et al. 1996, Friedrich and Tautz 1997, Miller et al. 1997, Bertone et al. 2008). Wiegmann et al. (2011) and Lambkin et al. (2013) have provided the most recent overall interpretation of family relationships based on both morphological and molecular evidence, but these have major issues of interpretation (Borkent 2018). See below for summaries of the limits and phylogeny of the infraorders.

Infraorder (F Brodo)

The major change to this infraorder since JF McAlpine et al. (1979) is the division of the into four families: , , , and . Most European workers had recognized the family status of the first three taxa for decades, as Byers (1992) carefully documented while still favouring the inclusion of all craneflies in a single family. Starý (1992) elevated the pediciines from a tribe of the limoniines to full family status. The recognition of four families of crane flies remains a contentious issue among taxonomists. Molecular analyses (Bertone et al. 2008, Wiegmann et al. 2011) as well as a recent morphological study (Lukashevich and Ribeiro 2018) indicate that are paraphyletic, thereby calling into question the family ranking of these crane fly taxa. In the present work we have decided to follow the four-family concept, mostly to remain aligned with the classification used in the online Catalogue of the Craneflies of the World (Oosterbroek 2018) and BOLD. also include (winter crane flies), a small family now formally recognized as the sister group to the s. lat. (crane flies) (Bertone et al. 2008, Wiegmann et al. 2011, Wiegmann and Yeates 2017).

Most recent taxonomic work in this infraorder has focused on the crane flies, bringing the total number of Canadian species to 633, mainly in the families (354 species in Canada) and (216), representing an increase of 21% since JF McAlpine et al. (1979) (Table 1). Monographs of Dalman (Byers 1983), Osten Sachen (Young 1987) and ( Meigen) (Starý and Brodo 2009) in the and of Meigen (Tangelder 1983, Oosterbroek 1984), Loew (Brodo 1987), and ( Alexander) (Gelhaus 2005) in the , have added species to our fauna, as did the documentation of crane flies of the Canadian Arctic (Brodo 1990, 2000) and additions to the eastern Canadian aquatic crane flies (LeSage and Harrison 1981, Sinclair 1988, Gathmann and Williams 2006). There are nearly as many BINs as there are recorded species of crane flies in Canada, although not every species has been barcoded, and it is expected that over 200 additional species will eventually be documented, mostly in the (Table 1). The number of (21) has not changed much since 1979, but 10 more species are expected in Canada (Table 1).

Crane flies are mostly aquatic or semi-aquatic but a few, notably the pest species, are terrestrial and associated with roots of grasses and herbaceous plants. Many larvae are saprophagous, fungivorous, ( Meigen and Matsumura species), or carnivorous (some and species), and are phytophagous. Meigen and (Linnaeus) are established pests of dairy lands and golf courses (Gelhaus 2001). The larvae of winter crane flies feed on detritus and fungi and are often associated with small animal burrows or bird’s nests (Dahl 1973).

and (BJ Sinclair)

The placement of these two families remains controversial. Previously, they have both been assigned to the infraorder (Wood and Borkent 1989, Oosterbroek and Courtney 1995), alone as sister to the (Sæther 2000), and one or both families as sister to all (Bertone et al. 2008, Wiegmann et al. 2011, Lambkin et al. 2013, Sinclair et al. 2013). are often considered sister to (Wood and Borkent 1989, Oosterbroek and Courtney 1995) or possibly sister to (Schneeberg et al. 2011, 2012). With the generally accepted assignment of to the re-defined (see below), we have chosen not to assign these two families to infraorder.

Only one species of minute (<2 mm long) is recorded from Quebec and New Brunswick (Courtney 1994). The second nymphomyiid species listed in JF McAlpine et al. (1979) was re-interpreted and transferred to (Kevan and Cutten 1981). The were revised by Courtney (1990) and are confined to the mountains of western Canada where three species are known and another expected (Table 1). Both families have aquatic immature stages that are morphologically adapted to fast-flowing waters.

Infraorder (G Curler and BJ Sinclair)

The limits of the have either been based on adult thoracic features (Hennig 1973, JF McAlpine et al. 1979) or defined by a suite of larval characters (Wood and Borkent 1989). The latter grouping has been viewed as a heterogeneous assemblage of non- (, ) and (, and ) families (Michelsen 1996). Recent analyses support a three-family concept, namely , and (Bertone et al. 2008, Wiegmann et al. 2011); however, these families did not form a clade in the analyses in Lambkin et al. (2013). Additional support for a relationship between and is based on wing venation (Bertone et al. 2008, Borkent and Sinclair 2012). The three family concept of this infraorder is followed here.

The number of species of known from Canada (7) has decreased from the 1979 estimate, due to several synonymies (Hogue 1987, Courtney 2000), and three more species are expected (Table 1). Two of the four Nearctic species of occur in Canada and one more may eventually be found here (Table 1). The immatures of blephacerids are conspicuously adapted to fast-flowing waters while those of the occur in slower moving streams. The larval biology and morphology of western tanyderid species are documented in Wipfler et al. (2012).

The fauna of Canada is known to include three subfamilies, 15 genera and 34 species (Quate 1955, Young and Perkins 1984, G Curler unpubl. data; Table 1). and are represented by three and one species, respectively; all other records are . There are more than three times as many BINs as recorded species in this family indicating that a relatively large number of species (we estimate 10–50) remain to be documented (Table 1). Species of França are hematophagous and mainly tropical or subtropical, with Canadian records representing the northernmost limits in the western Hemisphere for . Most species of Nearctic are detritivores living among moist decaying plant material or in madicolous habitats along stream margins, headwaters or seeps. In addition, several species of occur in homes and other habitats with anthropogenic influence (e.g., sewage treatment facilities, latrines, farmyards, polluted drainages).

Infraorder (BJ Sinclair)

Wood and Borkent (1989) proposed the infraorder for two small families of flies, and . Molecular and morphological evidence supporting the transfer of the to the (Bertone et al. 2008, Borkent and Sinclair 2012), has resulted in this infraorder being represented solely by the family . The phylogenetic placement of this infraorder among the nematocerous remains disputed, although the multi-chambered male accessory glands are similar to those of and (Sinclair et al. 2007). Currently four Canadian species in and four species in are known for this entirely aquatic lineage, but an additional eight species are expected to eventually be found in the country (Table 1). The North American species of the subfamily have recently been revised and keys to species provided (Fasbender and Courtney 2017).

Infraorder (A Borkent and DC Currie)

This infraorder includes eight families, all of which occur in Canada (Table 1). This is one more than recognized in JF McAlpine et al. (1979) due to the subsequent recognition of as distinct from the (Wood and Borkent 1989). Phylogenetic relationships among the families of are well known and have considerable support (Borkent 2012, Kutty et al. 2018) but the position of needs further testing, as either the sister group of all remaining families, or as the sister group of .

With 798 named species, the (non-biting midges) currently stand as the most species-rich family of in Canada, and at least 1000 additional species are expected to occur in the country (Table 1). The remaining families of non-biting midges, namely (11 species in Canada), (13) and (34) are represented by relatively few species (Table 1). Focused collecting at microhabitats of the latter two families has greatly increased the number of Canadian records (Moulton 2017, Pivar et al. 2018) and as many as 15 additional species are expected to occur in the country.

The remaining four families have some or all species with biting females. The (82 species in Canada), (164) and (263) are all quite diverse, whereas a single species of (formerly in ) is known for the country (Table 1). The (mosquitoes) and (black flies) are both very well known, but while only three additional mosquito species are estimated to be unrecorded, a further 20 species of black flies are expected to eventually be documented in Canada (Table 1). The (biting midges) are by far the most poorly known of biting flies. There are close to ten times as many BINs as recorded species for the group and it is thought that less than half of the Canadian fauna is known to date (Table 1).

The medical and veterinary significance and dominant presence in aquatic systems of so many has meant that they are some of the best known of the , including interpretation of their immatures. Taxa may be identified using the following references: (Sæther 1972, larvae, pupae, adults), (Borkent 2008, adults; McKeever and French 1991, larvae, pupae), (Mattingly 1971, larvae, pupae, adults to genus; Wood et al. 1979, larvae, adults) (Wiederholm 1986, 1989, pupae, adults to genus; Andersen et al. 2013, larvae to genus), (Downes and Wirth 1981, adults to genus; Borkent 2014, pupae to genus), (Adler et al. 2004, larvae, pupae, adults), and (Arnaud and Boussy 1994, Pivar et al. 2018, Sinclair 1996, adults). are poorly understood and require fundamental revision (Greenwalt and Moulton 2016).

Immature are aquatic in both lotic and lentic habitats where they are prey for aquatic organisms, including fish. The are especially common, occupying virtually every aquatic niche, including tree holes, rivers, lakes, and even tidal habitats where their abundant larvae often have a strong influence on aquatic community structure. As adults, the are the most prevalent, ubiquitous and persistent blood feeders in Canada, where some species are vectors of arboviruses, including West Nile virus, currently the most common mosquito-borne infection of humans in the country (Roth et al. 2010). are also quite common and sometimes very abundant in large rivers and lake outlets, with the resulting blood feeding activities affecting both humans and livestock. Most are predaceous but the majority of Latreille species have biting females. One species, Wirth and Jones, is a vector of Bluetongue virus of cattle and other ruminants in south-central British Columbia (Sellers and Maarouf 1991). Female are known only to bite frogs.

(BJ Sinclair)

The phylogenetic relationships and systematic assignment of the family remains disputed (Sinclair 2013). It has been variously assigned to a monotypic due to the absence of synapomorphies (Wood and Borkent 1989, Borkent and Sinclair 2012, Ševčík et al. 2016), to a variably defined (Oosterbroek and Courtney 1995, Grimaldi and Engel 2005, Pape et al. 2011), to (incl. , , Zetterstedt) (Amorim 1993), or considered a sister family to s. str. (Wiegmann et al. 2011, Sinclair et al. 2013).

are a small family of Holarctic flies with a single eastern species, McAtee, recorded from Canada (Ontario, Quebec) but two species from the Pacific Northwest (Sinclair 2013, Fitzgerald and Wood 2014) are expected to occur in British Columbia (Table 1). Detailed descriptions of all life stages and keys to Nearctic species are provided by Wood (1981), Wihlm et al. (2012), and Fitzgerald and Wood (2014). The life history of the eastern Nearctic is well documented (Wihlm and Courtney 2011) and all known larval stages in are restricted to burrowing in water-permeated wood.

Infraorder s. lat. (BJ Sinclair)

The boundaries of the have revolved around the nematocerous families included in the by Michelsen (1996), but there has been little consensus. Hennig (1973) favoured a broad concept that included the , , , , , , and (non-Nearctic), whereas Wood and Borkent (1989) restricted the infraorder to , , and . Amorim (1993) included the following groups in the : , (in part), , and . More recently molecular analyses have again supported the broad concept sensu Hennig (1973), exclusive of (Wiegmann et al. 2011) or exclusive of both and (Bertone et al. 2008). Grimaldi and Engel (2005) also recognized a broad concept, although exclusive of . Recently Sinclair et al. (2013) showed that the male terminalia of show derived attributes of the s. str. Given these conflicting classifications we have chosen to use both narrow (s. str.) and broad (s. lat.) concepts of the group as followed in Ševčík et al. (2016). The phylogenetic relationships within the s. str. have been studied by Wood and Borkent (1989), Amorim and Rindal (2007), and Ševčík et al. (2016).

Three families are excluded from s. str. due to the absence of a highly modified and multi-chambered accessory gland and different configuration of the ejaculatory apodeme (Sinclair et al. 2013). and (= ) have low diversity in Canada (six and one species, respectively) but the are represented by 30 species, with 15–20 more expected (Table 1). Canadian can be identified using the genus key in Cook (1981) and species keys referred to therein. The have not received much recent taxonomic attention in the Nearctic, although species of Harris were revised by Pratt and Pratt (1980). The larvae of these families are saprophagous and found in moist decaying organic matter.

Infraorder s. str. (BJ Sinclair)

Seven of the ten families of s. str. found in Canada are species-poor, including (1 species in Canada), (26), (1; formerly in ), and the following four families, formerly included in by J.F. McAlpine et al. (1979): (3), (16), (28) and (2) (Table 1). The number of species of known from Canada has decreased by approximately a third from the 1979 estimate (Table 1), primarily due to numerous synonyms discovered subsequently (S Fitzgerald pers. comm.). For all families, a few additional species are eventually expected to be found in Canada.

The remaining three families are much more diverse. The number of (129 species in Canada) has quadrupled since 1979 (Table 1), primarily due to ongoing revisionary studies by Scandinavian and German colleagues (see Mohrig et al. 2013 and subsequent papers by these authors). The numbers of known (243 species in Canada) have more than doubled since 1979 and those of now reach 489 species, thereby representing the highest documented diversity of any family in this infraorder (Table 1). Diversity estimates based on BINs are all much higher than the known fauna for these three families, and especially for the , where they suggest that the known species represent only approximately 2% of the Canadian fauna (Table 1). Hebert et al. (2016) estimated 16,000 species of in Canada, a 10-fold increase from the diversity predicted in 1979, a remarkable figure, but one consistent with the newly appreciated diversity of this family in temperate (Jaschhof and Jaschhof 2009, 2013) and tropical (Borkent et al. 2018, Brown et al. 2018) sites. As we are uncertain whether BINs indicate number of species, it is difficult to predict the number of species in Canada and it is possible that anywhere from 1000–16,000 species remain to be documented in the country. The great diversity of this family is in part due to the apparent host specificity of plant-feeding species, with several of economic importance. Hundreds of species of sciarids and mycetophilids also await documentation in Canada (Table 1).

Although knowledge of the species diversity of appears sparse, general information and identification to genera of the subfamily are provided by Gagné (1989, 2018). The genera of can be keyed in Vockeroth (1981), but some subfamilies are now recognized as families (see above). Several genera of have been revised since 1979, including: Vockeroth (Kerr 2011), Curtis (Borkent and Wheeler 2012), Rondani (Väisänen 1984), Winnertz (Fitzgerald and Kerr 2014), Meigen (Zaitzev 1982) and Winnertz (Gagné 1981).

Members of the s. str. are most abundant in moist woodlands, with many larvae found in fungi, in dead wood and other decaying plant material, beneath bark, and in a variety of other microhabitats. The majority of are associated with plants, forming galls or developing in flowers and leaf rolls, whereas others are inquilines on plant hosts damaged by other gall midges. Some are also associated with fungi, or free-living predators. A number of species of are serious pests of cereals, , conifers, apple trees, etc., and a zoophagous species is used in the biocontrol of aphids (Darvas et al. 2000).

Suborder : Lower

are a monophyletic suborder traditionally defined by a short antenna with a modified flagellum (third antennal segment) made up of 3–8 fused flagellomeres. The group is very diverse with 83 families occurring in Canada (Table 1). The are usually divided into the paraphyletic Lower and the monophyletic , which contains both the monophyletic and .

The Lower are a large and undoubtedly unnatural assemblage of mostly large and conspicuous flies. Until recently, this group was widely referred to as the , but morphological and molecular evidence indicate that it is paraphyletic, at least with respect to the (Woodley 1989). With the assignment of the to the (which includes both and ) (Griffiths 1972), the term Lower is now used to refer to the non-Eremoneuran . Considerable research globally has focused on this group, especially among the therevoid clade (e.g., Woodley 1989, Sinclair et al. 1994, Yeates 1994, 2002, Wiegmann et al. 2000, 2011, Winterton et al. 2007, Trautwein et al. 2010, Shin et al. 2017). Division of the Lower is largely stable, with well supported (Woodley 1989), (Sinclair et al. 1994, Wiegmann et al. 2000, 2011, Kerr 2010), (Sinclair et al. 1994, Wiegmann et al. 2011) and (Woodley 1989, Wiegmann et al. 2011). Several families remain difficult to assign phylogenetically and continue to float between infraorders, i.e., , , . Major changes since JF McAlpine et al. (1979) include the recognition of a new family (Zloty et al. 2005) and elevation of the (Kerr 2010) and (Evenhuis 2002) from and , respectively.

This infraorder is represented by the single family , although some authors have divided it into smaller family units (Woodley 1989). The are considered the sister group to the in most analyses (Wiegmann et al. 2000, 2011, Sinclair et al. 2013, Shin et al. 2017). Five genera and 14 species are recorded from Canada (Woodley 2011c), similar to numbers recorded in 1979, and another one or two species are expected (Table 1). Current knowledge of the group, generic diagnoses, a key to world genera and catalogue of species have been compiled by Woodley (2011c). Xylophagids are found primarily in wooded and forest regions where the larvae are predators of wood inhabiting insects.

Woodley (1989) and Sinclair et al. (1994) summarized the morphological evidence for relationships of the . Much of the uncertainty of higher level phylogeny of the is due to doubts concerning the limits and monophyly of the . Through combined morphological and molecular analyses, Kerr (2010) redefined the family , establishing its monophyly and recognizing the families (Australia and Chile) and . The classification of Kerr (2010) is followed here.

Six families of occur in Canada and these are organized in two superfamilies. In , include three known species in Canada and two more are expected (Table 1). include 48 species, a substantial increase from 1979, and 10–15 additional species are expected (Table 1). No modern species keys are available for the large genera in the and most of the family is in need of revision. Adults are common in forested regions, where most larvae occur in damp forest litter and beneath mats of mosses. The immature stages of the are unknown.

In , three families have low diversity: (5 species in Canada), (2), and the recently erected monotypic family (1) (Zloty et al. 2005; Table 1). In part due to their large size and the biting habits of most females, the (horse flies and deer flies) are much better known than most insects in Canada, with keys and illustrations known for all 142 species (Teskey 1990, Thomas and Marshall 2009, Thomas 2011) as well as a complete catalogue (Burger 1995). With the slight increase in species richness since 1979, this family is now considered to be very well known and no additional species are expected in Canada. The larvae of and occur in riffle zones and/or vegetation of cool streams and flowing rivers. Those of and are predators of invertebrates found mostly in wetland soils.

Infraorder (M Hauser)

The infraorder includes three families, of which the and the occur in Canada while the are restricted to the Neotropics. The sister-group relationship of and is strongly supported, especially by larval characters (Woodley 1989).

The are represented by 114 species in Canada, a substantial increase from 1979 (Table 1), and 5–10 more are expected (Table 1). At least five species of have been introduced from Europe, Australia and the USA (Swann et al. 2006, Marshall et al. 2015). The fauna is rather well known, although revisions are needed especially for groups with aquatic larvae ( James, Geoffroy, Meigen, Geoffroy), which could reveal a few undescribed species as well as some synonyms. Only two genera and seven species of are known from Canada (Woodley 2011b) but numbers have nearly doubled since 1979 (Table 1); a key to the Canadian species is provided by Webb (1984).

Stratiomyids are usually found in humid and forested areas where their larvae are terrestrial or aquatic, feeding mostly on decaying plant and animal materials (Woodley 2001). The larvae of are found under the bark of trees but little is known of the biology of these uncommon flies.

Both families have been assigned to the based on the parasitic larvae with hypermetamorphosis (Woodley 1989), but this infraorder (including ) is now generally considered polyphyletic with the three parasitic families considered to be distantly related (Yeates 1994, 2002, Winterton et al. 2007, Wiegmann et al. 2011, but see Shin et al. (2017) for a divergent opinion). Only two species of are found in Canada (Table 1), the same as in 1979, and these are confined to the central arid regions of British Columbia. Twenty species of are recorded from Canada; a key to New World genera is available in Schlinger et al. (2013), but only one recent revision has included Canadian records (Borkent et al. 2016). A few more acrocerid species are therefore expected in the country. The larvae of are internal parasites of spiders, whereas those of are parasitic on grasshoppers and beetles.

The higher classification and phylogeny of the (containing one superfamily – ) has received a great deal of focus over the past decades (e.g., Woodley 1989, Winterton et al. 2007, Trautwein et al. 2010, Winterton and Ware 2015). Discussion of the limits of the , which appear paraphyletic in relation to (Sinclair et al. 1994, Trautwein et al. 2010), has primarily revolved around the placement of the genus Schiner, which has previously been assigned to the , , or its own separate family considered sister to the , or (Trautwein et al. 2010).

Eight families of generally large and showy occur in Canada, five of which are relatively species-poor, including (1 species in Canada), (2), (1), (7), and (10) (Table 1). The diversity of and in the southern interior of British Columbia was documented by Cannings (2006), whereas the , and are poorly documented and more species are expected in Canada (Table 1).

The Canadian fauna of the larger families of has received much attention since JF McAlpine et al. (1979). The number of (222 species in Canada) has nearly doubled, primarily through the recent publications of Cannings (1994, 1997, 2002), and a few additional species may eventually be added (Table 1). The diversity of the in Canada is outlined in a world catalogue (Evenhuis and Greathead 1999), but the Canadian fauna had largely been ignored for decades until the publication of an illustrated key to eastern Canadian species (Kits et al. 2008). The 105 species of currently documented represent a 50% increase since 1979 and more than 40 additional species are expected in Canada (Table 1). A world catalogue of outlines the Canadian diversity of this family (Webb et al. 2013). With 50 species now recorded from Canada, this family is very well known and no additional species are expected (Table 1).

The display a wide range of habitats and life histories. The have predaceous larvae associated with wood-boring larvae, bird’s nests, and carpet beetle larvae. The larvae of are unknown and adults are sporadically collected, with verified records indicating that they frequent riverbanks. Adult are flower visitors, feeding on pollen and nectar, whereas the few larval observations suggest egg pod predators of grasshoppers and inquilines in ant nests. Adult are efficient predators with highly modified mouthparts; the larvae live in soils and rotting wood. Larvae of are often found burrowing through sandy soils (Irwin and Lyneborg 1981). The larvae of and are predaceous in sandy soils and adults are flower feeders. The are generally parasitic on various or predaceous on egg pods of grasshoppers (Hall 1981), with adults visiting flowers.

Suborder :

The monophyly of is strongly supported and the group comprises the monophyletic and (Cumming et al. 1995, Sinclair and Cumming 2006, Wiegmann et al. 2011, Lambkin et al. 2013). The now also include the monotypic Nearctic family (not in Canada), which is considered to be either the sister group of (Trautwein et al. 2010, Wiegmann et al. 2011), or the sister group of the entire (Sinclair et al. 2013). The as a group was not recognized in JF McAlpine et al. (1979).

Superfamily (JM Cumming and BJ Sinclair)

The are a monophyletic lineage comprising five main families, namely , , , , s. lat. (including and ) (Sinclair and Cumming 2006) and three previously unassigned genus-groups. Some authors have treated two of these genus-groups as separate families (i.e., (non-Nearctic) and ), because of the availability of family-group names (Thompson 2009, Pape et al. 2011, Marshall 2012). The group has recently been elevated to subfamily rank within yet another newly recognized family, (Wahlberg and Johanson 2018). Recognition of this family is controversial and generally not accepted by the empidoid community, nor is it accepted herein.

Five families of this primarily predaceous group occur in Canada (Table 1): (7 species), (251), (11), (155), and s. lat. (508), plus the genus-group (17). Apart from the (exclusive of and ), the remaining groups were lumped into the in JF McAlpine et al. (1979). The current total of 949 Canadian species of is a moderate increase over the 800 species recorded by JF McAlpine et al. (1979). Many empidoid genera still require study and recent Nearctic revisions (e.g., Sinclair et al. 2011, Sinclair and MacDonald 2012, Brooks and Cumming 2017) have resulted in numerous new species descriptions. The key to the Nearctic genera of in Steyskal and Knutson (1981) follows the family concept used by JF McAlpine et al. (1979) and is now out-of-date. Hundreds of additional empidoid species are expected to be eventually documented in Canada (Table 1).

The and two subfamilies of ( and ) include species with aquatic larvae. The remaining are mainly terrestrial and many species are important pollinators (Rader et al. 2016), especially in alpine and arctic regions (Lefebvre et al. 2014). The are common predators in forests, grasslands and agricultural fields (Sinclair and Cumming 2017), whereas the are significant predators in various aquatic, semi-aquatic and terrestrial habitats (Grichanov and Brooks 2017).

Suborder : :

The constitute the most diverse lineage of and include the numerous families of higher flies that pupate inside the last larval exuviae (i.e., puparium). The group is divided into the basal Lower (“”) and the monophyletic (i.e., flies with a protrusible ptilinum for exiting the puparium). are further divided into the paraphyletic and the monophyletic .

Lower (“”)

No recent hypotheses support the monophyly of the , which traditionally included the cyclorrhaphan families exclusive of (or those flies without a ptilinum for exiting the puparium). Only Brown (1992, 1995) and Disney (1994) have supported the monophyletic concept proposed by McAlpine (1989). All other morphological and molecular analyses have shown that the “” are a grade and should be referred to as the Lower (Griffiths 1972, Cumming et al. 1995, Zatwarnicki 1996, Collins and Wiegmann 2002, Moulton and Wiegmann 2004, Wiegmann et al. 2011, Pauli et al. 2018). This is an important lineage to understand phylogenetically as it sets the stage for the massive radiation of . Unfortunately, there has been a profound lack of agreement about relationships within this grade.

(J Skevington and JM Cumming)

Placement of has been one of the most intractable problems within phylogenetics. The family has floated around in different analyses, in some cases being proposed as sister to the rest of (Griffiths 1972), as sister to the (Brown 1992, Cumming et al. 1995), or as sister to (or within) the + (Collins and Wiegmann 2002, Moulton and Wiegmann 2003, Wiegmann et al. 2011). Seven species of lonchopterids are known from Canada (Klymko and Marshall 2008) and another could eventually be discovered. Larvae are found in wet, decaying organic matter where they feed on bacteria and fungi. Two species occur in aquatic environments such as springs, seeps and shorelines (Valliant 2002). Adults feed on fungi, nectar, pollen and dead insects (Klymko and Marshall 2008).

Superfamily (J Skevington and JM Cumming)

The status of this superfamily is contentious and its use should probably be abandoned. In the strict sense it appears to include (including Zetterstedt and Kessel) and (non-Nearctic) (Tkoč et al. 2017), but even this is controversial, as has also been placed outside the superfamily in numerous positions in various phylogenies. There are 39 named platypezid species known from Canada and while a few more species are still expected (Table 1), some recent synonymies were established (e.g., Cumming and Wheeler 2016) and more are likely to occur as previous revisionary work, primarily by EL Kessel and associates (e.g., Kessel and Buegler 1972), routinely described males and females as separate species. Immature platypezids are fungivorous and the males of many species form large swarms.

Phylogenetic analyses that include the relevant taxa support the relationship of (including sensu Brown et al 2015, Disney 2001) and (non-Nearctic) in this superfamily (Wiegmann et al. 2011, Young 2018). There are 135 named species of known from Canada with the diversity estimated to be much greater, with perhaps 300 additional species (B Brown pers. comm.; Table 1). Phorids likely have the widest diversity of larval lifestyles of any insect family. Although some of the most common species are decomposers (including carrion feeders), others are fungivorous, phytophagous (including leaf miners), inquilines in social insect nests, predators, or parasitoids.

Superfamily (J Skevington)

This is another higher grouping that should likely be abandoned. and have been proposed as sister taxa in all published morphological phylogenetic hypotheses (Sinclair et al. 2013 and references therein), but most molecular analyses refute this relationship and place as sister to and as sister to + (Wiegmann et al. 2011, Pauli et al. 2018). Only Moulton and Wiegmann (2004) have proposed that are sister to and that are sister to + . Recently discovered morphological evidence based on metapleural characters (Tachi 2014) supports the sister-group relationship of and .

There are currently 539 described species of recorded in Canada, a modest increase since 1979, and another 34 species are thought to occur (Table 1). The number of species in Canada has almost doubled since 1979 and currently totals 85 species, but much of the fauna remains to be discovered and at least another 170 species are expected to occur. Most adult syrphids are pollinators, but larvae range from predators of aphids and other soft-bodied insects, predators and parasitoids of ants, to saprophages in rotting wood, slime fluxes, and sewage. Most pipunculids are parasitoids of (Skevington and Marshall 1997) and Zetterstedt are parasitoids of (Koenig and Young 2007).

:

The are a large monophyletic subgroup of characterized by an inflatable sac-like ptilinum that temporarily extrudes from the head of the adult fly to allow emergence from the puparium. This exceedingly successful lineage contains 54 families in Canada, which are traditionally divided into the paraphyletic and the monophyletic .

are a large and heterogeneous assemblage of families circumscribed by the absence of characters used to define the . Many families are readily characterized by appearance or habit, but support for relationships amongst them has been elusive, likely because several lineages originated in a short period as part of an explosive radiation following the K-T extinction event 65mya (Wiegmann et al. 2011). As such, support for family-level relationships is often weak, with the exception of a few groups within , , and . Evolutionary reconstruction and superfamily composition has therefore been contentious and varied historically (JF McAlpine 1989, Yeates et al. 2007). Nine superfamilies are currently recognized, all of which occur in Canada, and the number of families in the country totals 44 (Table 1). The Canadian acalyptrate fauna is relatively well known, although it is likely that many species remain undescribed, especially amongst taxa with diminutive species.

Superfamily (O Lonsdale)

, historically called by some, are a weakly supported cluster of families of low-to-medium species richness. Current superfamily definitions largely stem from a classification developed by Hennig (1958), refined in subsequent studies (Hennig 1965, 1973), and later elaborated upon by JF McAlpine (1989) and DK McAlpine (1997a, b), who suggested alternate superfamily placement for some families. The classification of JF McAlpine (1989) is followed here, although phylogenetic studies testing this system are ongoing and classification is expected to change. were once considered a subfamily of by some, but Lonsdale (2013) found that these sister-taxa are best represented by a two-family system.

The superfamily includes nine families, four of which occur in Canada (Table 1): (27 species), (2), (2), and (1). The Canadian fauna of these families appears to be relatively well-known and only a few species have been added in recent decades, but work on is still required. Revisions and keys to Nearctic genera and species are available for (Feijen 1989), (Barber 2006) and (Lonsdale 2013, Knab and Shannon 1916). Nearctic were treated in Melander (1920) and subsequent revisions treating species of Nearctic Meigen are available in Capelle (1953) and Buck and Marshall (2006b). Buck and Marshall (2006a) partially revised Meigen. Little is known of the life histories of non-pest species. Most taxa for which information is known appear to be saprophagous in damaged or decaying plant material, but some are primary invaders of plants, and a few of these are occasional crop pests.

The are the only nerioid family known in Canada. Some authors, including Hennig (1958), treated a number of micropezid subfamilies as full families under the assumption that the stilt-legged flies () rendered them paraphyletic, but most contemporary authors now follow DK McAlpine (1975, 1998) in recognizing a broad monophyletic .

Only sixteen of the approximately 700 described species of occur in Canada, one of which is a recently introduced European Meigen (Hoebeke and Wheeler 1994). Species numbers have otherwise remained unchanged since 1979 and no additional species are anticipated (Table 1). Adult generally display distinctive stilt-like mid and hind legs, and most of the relatively few species for which oviposition or larval habitats are known occur in rotting wood (Marshall 2012) and a variety of other decomposing materials.

Superfamily (JF Gibson)

The families presently composing were treated separately as and by JF McAlpine et al. (1979) and JF McAlpine (1989). The inclusion of the orphaned family within the was supported by Wiegmann et al. (2011) and has been generally accepted since (e.g., Marshall 2012). Other taxonomic changes within the superfamily since 1979 include the recognition of the (1 species in Canada) and (1) as families distinct from (Malloch 1933, DK McAlpine 1991a, b), bringing the total number of families found in Canada to seven (Table 1). Members of the are some of the largest acalyptrates, but species diversity is relatively low with fewer than 200 species in Canada. Current numbers of species have not changed much since JF McAlpine et al. (1979) for (4 species), (8), and (19). For (120) and (42), species numbers in Canada have increased by approximately 40% since 1979 (Table 1). A few additional species are expected to eventually be documented in four of the seven families.

Knutson et al. (1986) produced a catalogue of North American . Most other recent faunistic and taxonomic work on sciomyzoid families has been global in nature but with relevance to the Canadian fauna: (Mathis and McAlpine 2011); (Gibson and Skevington 2013); (Mathis and Sueyoshi 2011); (Mathis 2011a); (Mathis 2011b); (Knutson and Vala 2011). As well, western Canadian were treated by Gibson (2017). There has been no work on Canadian . Complete life history and range are not known for most species, but some taxa (, ) are parasitoids. Restriction to marine coasts is also common within the group (, , , – ).

The recent molecular analysis of Wiegmann et al. (2011) supported a monophyletic , including two families found in Canada, and . The current number of reported species in Canada for (78) and (35) represent modest increases since 1979, but a few more species of each family are likely to be recorded in the future (Table 1). Most of the Canadian fauna has not been revised since JF McAlpine et al. (1979). A notable exception is the revision of Coquillet () by Barber (1985), which added ten species to the Canadian list and detailed much of the life history known for the group. Species of are suspected to be saprophagous as immatures while those of are parasitoids of aphids and other .

The superfamily was divided by Korneyev (2000a) into a monophyletic “higher ” and a paraphyletic “lower ”, all eight families of which are represented in Canada (Table 1). Korneyev (2000b) provided analysis and discussion of the family-level and genus groupings within , but admitted that much remains to be investigated. The “higher” families are (35 species in Canada), (10), (3), and (122). The “lower” families are (31), (9), (99) and (1). Recently, a phylogeny by Han and Ro (2016), based on molecular data, questioned this system, supporting as paraphyletic, finding to belong to the “higher” group of families and a sister-group relationship to the remaining families. The numbers of known species have been relatively constant since 1979, with the exception of the family , which has tripled (Table 1). A few more species are expected to be discovered in Canada for most families, especially for , and .

Revisions of the Nearctic fauna are available for (Malloch and McAtee 1924), (Steyskal 1978) and (Foote et al. 1994). The global were revised by JF McAlpine (1977), and Rochefort and Wheeler (2015) reviewed the of northern Canada. The Manual of Nearctic , including references therein, is the best recent resources for identification of (JF McAlpine 1987), (Steyskal 1987b) and (Steyskal 1987a). Most Canadian belong to Robineau-Desvoidy and are keyed in Namba (1956), and most eastern Canadian species are easily identified using Jackson et al. 2011.

Species of most families are very conspicuously patterned, especially on the wings, and are behaviourally fascinating with elaborate courtship rituals. and are darker and less “charismatic”, and much remains to be discovered of their biology. Many taxa are saprophagous as larvae, but less commonly predaceous in damaged or decaying plant vegetation, e.g., (Teskey (1976); a few are primary invaders of plants and may be pestiferous, especially (DK McAlpine 1973, Norrbom and Korytkowski 2010, Marshall 2012). prefer animal matter in advanced states of decay (JF McAlpine 1977). A minority of are saprophages, parasitoids, inquilines or predators, and are parasitoids of scarab larvae (Korneyev 2000b, Marshall 2012).

JF McAlpine’s (1989) superfamily is largely derived from Hennig’s (1971) concept of , but it is a highly problematic and likely polyphyletic entity that remains in use mostly as a convenient grouping for numerous families and genera of uncertain placement. Winkler et al. (2010) used molecular data to show that the superfamily is non-monophyletic. The boundaries of and have undergone considerable permutation, resulting in some stability and recognition of the new family (discussion in Rung and Mathis (2011)), but placement and status of the genera allied to Coquillet are still uncertain (Winkler et al. 2010, Marshall 2012).

With 450 species, the are by far the most diverse opomyzoid family in Canada. More than a hundred species have been added since 1979 but the large number of BINs (772) (Table 1) suggest that much taxonomic work remains to be done, especially in the large genus Fallén, which contains many undescribed species. The remaining families are relatively species-poor and often uncommon in Canada. These consist of the (5 species in Canada), (2), (3), (6), (11), (37) and (22). Numbers of Canadian species for these small families have remained relatively constant since 1979 with the exception of the , which increased nine-fold through the revisionary work of Roháček and Barber (2016), and the , which were fully revised over the past 20 years (e.g., Lonsdale et al. 2011, Lonsdale 2017b; Table 1). A few additional Canadian species are expected for each family except the (Table 1).

The Canadian were revised by Spencer (1969), but since that time generic concepts have been extensively reconsidered, especially in Winkler et al. (2009) and Lonsdale (2014), and several genera have been revised: Hendel (Boucher 2012b); Rondani (Boucher 2002, 2003, 2008, 2012a); Mik (Lonsdale 2017a); Hendel (Boucher 2004). Many north temperate species of (sometimes as “ Hardy”) were treated in a long series of papers by GCD Griffiths. Apart for the and the (see above), little has been published about the remaining families since 1979. Rung and Mathis (2011) globally revised Macquart (the only occurring in Canada) and a new invasive was recorded by Wheeler et al. (1999).

Winkler et al. (2009) summarized known biologies, which often includes phytophagy with a number of being highly pestiferous, but there are also associations with fungi, sap fluxes, frass, and insect galleries in trees. Some taxa are predaceous and a few have larvae that are aquatic to semi-aquatic; Rotheray and Horsfield (2013) found to feed on biofilm in decaying wood.

The families currently in (Marshall 2012) were divided amongst the superfamilies and in JF McAlpine et al. (1979). Another recent change to the classification of the group involves the inclusion of the family formerly known as the in the (DK McAlpine 2007a). JF McAlpine (1989) determined “Carnites” Newman (1834) as the oldest family-level name in the group, thus making the proper superfamily name rather than .

Of the five families in Canada (Table 1), three have few species and only minor changes have occurred since 1979: (1 species in Canada), (12), and (13). were globally catalogued recently (Munari and Mathis 2010) and the number of reported Canadian species has doubled since 1979 to a current total of 10. More carnids and milichiids remain to be discovered in Canada and species numbers are expected to at least double for these families (Table 1). Much recent work has been completed on , both globally (e.g., Nartshuk 2012) and within Canada only (e.g., Grégoire Taillefer and Wheeler 2011, Barrie and Wheeler 2016). These publications have resulted in 40 more species of reported here compared to JF McAlpine et al. (1979), but many more species of this family are suspected to be undescribed or unreported based on BIN numbers and field observations. Members of display a wide range of life histories including saprophagous larvae, coprophagous larvae, kleptoparasitism (), crop pests (some ), and parasites in bird’s nests ().

The families currently in (Marshall 2012) were divided amongst the superfamilies and in JF McAlpine et al. (1979). The present configuration reflects the most recent phylogenetic hypotheses and correctly identifies as the oldest valid family-group name in the taxon (JF McAlpine 1989, Grimaldi 1990). The recent molecular analysis of Wiegmann et al. (2011) supported a monophyletic .

Of the six families in Canada (Table 1), four have few species recorded from the country and have not seen a marked change in species numbers since JF McAlpine et al. (1979): (1 species in Canada), (7), (1), and (2). A few additional species of are expected (Table 1). Both and have seen numbers of species reported in Canada increase by approximately 30% since JF McAlpine et al. (1979), to 79 and 197 species, respectively, and more unreported and undescribed species are likely to be found (Table 1). Nearctic have been the subject of considerable phylogenetic, taxonomic, and faunistic research (e.g., Remsen and O’Grady 2002, Brake and Bächli 2008, Miller et al. 2017) and many of the genera and subgroups of Nearctic have been revised recently (e.g., Mathis and Zatwarnicki 1995, Costa et al. 2016). Most species of are suspected to be saprophagous as larvae, although there have been records of leaf-mining and predaceous species. Some species of are noteworthy as extremophiles, including hot spring, salt water, and petroleum-inhabiting species. Some are important model species in genetic research and the family also includes a number of agricultural pests.

Superfamily (SA Marshall and O Lonsdale)

In Canada, this superfamily contains three families (Table 1). While detailed study is required, consensus thus far is that the family is rendered paraphyletic by the (Roháček et al. 2001). While some authors have suggested that and should be combined (DK McAlpine 2007b), others have suggested dividing the into multiple families, as discussed in JF McAlpine (1989), DK McAlpine (1985, 2007b), and Papp (1998). It appears most likely that the will be broken up once the phylogeny of the group is better resolved.

The infrequently encountered include five recorded species in Canada with perhaps as many more awaiting discovery (Table 1). The more heterogeneous currently have 72 recorded species in Canada, including four species previously treated as by JF McAlpine et al. (1979), and as many as 38 additional species are expected (Table 1). Most species in the superfamily belong to the well-defined family , which include thousands of species worldwide (catalogued by Roháček et al. 2001). The Canadian have been fully revised since 1979, resulting in a five-fold increase in species numbers (from 35 to 184); relatively few additions are expected as further collecting is carried out (Table 1).

Canadian can be identified to genus using the keys in Marshall and Richards (1987) and in Marshall and Buck (2010); almost all Canadian species can be identified with keys cited in the latter work. The Canadian can be keyed using Malloch (1914) and Wheeler (1961), but the fauna should be re-examined as it is probable that undescribed species remain to be discovered. The Canadian were remarkably well covered by Gill (1962, 1965); there have been few changes since then but new synonymies and additional taxa are to be expected, especially once the genus Robineau-Desvoidy is revised.

develop as microbial grazers in a wide variety of moist microhabitats, including dung, carrion, fungi and many kinds of decaying plant material. Many inhabit mammal nests or burrows, and several species are associated with caves. have similar habits and also occur in caves, mammal nests, bird’s nests, fungi, and dung. Some have also been reared from bird’s nests. Immature stages of are poorly known with the exception of the specialized coastal species found in decomposing seaweed (Marshall 1982).

This large monophyletic subgroup of has received much systematic attention over the last three decades (e.g., McAlpine 1989, Nirmala et al. 2001, Kutty et al. 2008, 2010, Zhang et al. 2016). Whereby JF McAlpine et al. (1979) grouped all calyptrates into a single superfamily (), most recent published works (Kutty et al. 2010, Wiegmann et al. 2011, Lambkin et al. 2013, Cerretti et al. 2017) have supported a division of the group into the , the paraphyletic ‘muscoid grade’, and the (nested in the muscoid grade) proposed by Kutty et al. (2008). The composition of the has remained mostly unchanged since Roback (1951), and ten of the approximately 15 recognized calyptrate families worldwide (Cerretti et al. 2017) occur in Canada.

Superfamily (J Savage)

The are presently considered the sister-group to the remaining calyptrates (Kutty et al. 2008, 2010). It includes the (tsetse flies) and the (louse flies and batflies) with only the latter family found in Canada. JF McAlpine et al. (1979) recognized the families and , which are now included as subfamilies of the (Kutty et al. 2010, Pape et al. 2011). The Canadian batflies, represented by two species of wingless spider-like nycteribiines and one small hairy strebline are only known from western provinces (British Columbia and Saskatchewan) (Wenzel 1965, Graciolli et al. 2007). With the exception of the (Graciolli et al. 2007), there has been little work done on the Canadian fauna since 1979. While 17 species are currently recorded from Canada, DNA barcodes from Canadian hippoboscid specimens are few and all placed in a single BIN, further emphasizing the need for additional field collecting and taxonomic work on this group.

All are larviparous and deposit mature larvae that are ready to pupate. The adults have a striking appearance that reflects their ectoparasitic habits and many species have limited or no flying abilities. The stocky, dorsoventrally flattened will feed on the blood of many birds and mammal species while the and are restricted to bats.

“Muscoid Grade” (J Savage)

While we acknowledge the paraphyly of the muscoid grade, the group is used here for convenience as no alternative classification scheme has yet been proposed to assign the muscoid families to higher taxa. Members of this assemblage can be recognized mostly by the absence of diagnostic features found in the (e.g., adaptations to ectoparasitic habits) and the (e.g., meron with a row of strong setae). The most important change relating to the Canadian fauna since JF McAlpine et al. (1979) is the recognition of the as distinct from the (Griffiths 1972, McAlpine 1989)

All four muscoid families are found in Canada. In his census of Canadian , JF McAlpine et al. (1979) reported more muscid than anthomyiid species (525 vs 375) but the subsequent recognition of the as a separate family (84 species in Canada) and numerous synonymies have reduced the number of Canadian muscids to 440. The publication of more than a hundred new anthomyiid species and records (Griffiths 1982–2004) have resulted in a total of 515 documented species of and the group has supplanted the muscids as the most species-rich muscoid family in Canada. The currently have 126 recorded species in Canada but have received less taxonomic attention than the other taxa. BINs are close to the numbers of described species for all families in this group and an increase in species numbers of only 10–20% is expected in the future (Table 1).

The are the only muscoid family to have been recently revised for Canada (Griffiths 1982–2004, excluding Lioy and Robineau-Desvoidy). A few generic and type revisions (e.g., Cuny 1980, Pont 1984, 2011, Savage 2003, Moores and Savage 2005) as well as some faunistic contributions (e.g., Renaud et al. 2012a, b) have nonetheless improved our knowledge of the taxonomy and distribution of Canadian and . The , unfortunately, have remained mostly unstudied.

In Canada, muscoid flies are especially well represented in northern and alpine habitats (Huckett 1965, Griffiths 1982–2004). The saprophagous housefly ( Linnaeus) is the best known member of the group, but immature and adult muscoids exhibit a range of ecological habits so broad that it almost spans the complete spectrum displayed at the order level (see Marshall (2012) and Courtney et al. (2017) for general overview).

Superfamily (JE O’Hara)

This large lineage of nearly 15,000 species worldwide (Pape et al. 2011) has long been recognized as monophyletic based on morphology (Griffiths 1972, McAlpine 1989) and this view has since been corroborated by molecular analyses (Kutty et al. 2010, Wiegmann et al. 2011, Marinho et al. 2012). Some major family-level changes have been recently implemented in the (see Ceretti et al. 2017), but the same five families recognized by JF McAlpine et al. (1979) are still recognized today (Table 1).

With 736 known species, the have a large presence in Canada (O’Hara and Wood 2004, J O'Hara and M Wood unpubl. data), placing them second behind the as the most speciose family of in the country based on numbers of described species (Table 1). More than 200 species have been added to the Canadian fauna since 1979, mostly as a result of tribal (Wood 1985, O’Hara 1989, 2002) and generic revisions (e.g., O’Hara 1983, 1994, 2012, Sun and Marshall 2003). Despite these advances, dozens of undescribed Canadian species are still awaiting description in collections. Much recent attention has also been dedicated to the (135 species in Canada) and the (62) and their species numbers have increased by over 50% since 1979 (Table 1). Catalogues and revisions that account for most of the increase in Canadian numbers of sarcophagid species include Pape (1996), Dahlem and Naczi (2006), and Giroux and Wheeler (2009, 2010). A few additional species of sarcophagids are expected in the country. The Canadian calliphorid fauna is very well known and recent taxonomic tools to identify it include Sabrosky et al. (1989), Rognes (1991), Whitworth (2006), Marshall et al. (2011), Jewiss-Gaines et al. (2012), and Tantawi et al. (2017). No additional species are expected in Canada. The (17 species in Canada) and introduced (2) have not undergone any significant changes since JF McAlpine et al. (1979) (Table 1). The correspondence between BINs and known species numbers is generally good in this superfamily except for the and, to a lesser extent, the (Table 1).

The are generally large robust flies that display a wide range of life histories and ecological habits. The and are all parasitoids of terrestrial arthropods and the larvae of are internal parasites of wild or domestic mammals. The calliphorids include a few parasitoid species in the Robineau-Desvoidy complex, all presumably introduced from Europe with their earthworm hosts (Rognes 1991), and some ectoparasites of birds ( Hough) but most are saprophagous and associated with decaying animal matter. The have the most diverse larval habits of the superfamily; some are kleptoparasites in the nests of solitary bees and wasps, some feed on carrion or dung, and others are associated with living animals as parasitoids (particularly arthropods) or predators. Several parasitic species of , and are also known to cause myiasis in humans and other vertebrates (Marshall 2012).