The major change to this infraorder since JF McAlpine et al. (1979) is the division of the Tipulidae into four families: Tipulidae, Cylindrotomidae, Limoniidae, and Pediciidae. 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 Limoniidae 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. Tipulomorpha also include Trichoceridae (winter crane flies), a small family now formally recognized as the sister group to the Tipulidae 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 Limoniidae (354 species in Canada) and Tipulidae (216), representing an increase of 21% since JF McAlpine et al. (1979) (Table 1). Monographs of Chionea Dalman (Byers 1983), Dicranoptycha Osten Sachen (Young 1987) and Symplecta (Symplecta Meigen) (Starý and Brodo 2009) in the Limoniidae and of Nephrotoma Meigen (Tangelder 1983, Oosterbroek 1984), Prionocera Loew (Brodo 1987), and Tipula (Eremotipula Alexander) (Gelhaus 2005) in the Tipulidae, 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 Pediciidae (Table 1). The number of Trichoceridae (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, (Limonia Meigen and Metalimnobia Matsumura species), or carnivorous (some Limoniidae and Pediciidae species), and Cylindrotomidae are phytophagous. Tipula paludosa Meigen and T. oleracea (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).

The limits of the Psychodomorpha 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-Neodiptera (Psychodidae, Trichoceridae) and Neodiptera (Perissommatidae, Anisopodidae and Scatopsoidea) families (Michelsen 1996). Recent analyses support a three-family concept, namely Blephariceridae, Psychodidae and Tanyderidae (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 Psychodidae and Tanyderidae 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 Blephariceridae 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 Tanyderidae 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 Tanyderidae occur in slower moving streams. The larval biology and morphology of western tanyderid species are documented in Wipfler et al. (2012).

The Psychodidae 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). Phlebotominae and Trichomyiinae are represented by three and one species, respectively; all other records are Psychodinae. 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 Lutzomyia França are hematophagous and mainly tropical or subtropical, with Canadian records representing the northernmost limits in the western Hemisphere for Phlebotominae. Most species of Nearctic Psychodinae are detritivores living among moist decaying plant material or in madicolous habitats along stream margins, headwaters or seeps. In addition, several species of Psychodinae occur in homes and other habitats with anthropogenic influence (e.g., sewage treatment facilities, latrines, farmyards, polluted drainages).

Wood and Borkent (1989) proposed the infraorder Ptychopteromorpha for two small families of flies, Ptychopteridae and Tanyderidae. Molecular and morphological evidence supporting the transfer of the Tanyderidae to the Psychodomorpha (Bertone et al. 2008, Borkent and Sinclair 2012), has resulted in this infraorder being represented solely by the family Ptychopteridae. The phylogenetic placement of this infraorder among the nematocerous Diptera remains disputed, although the multi-chambered male accessory glands are similar to those of Bibionomorpha and Culicomorpha (Sinclair et al. 2007). Currently four Canadian species in Bittacomorphinae and four species in Ptychopterinae 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 Bittacomorphinae have recently been revised and keys to species provided (Fasbender and Courtney 2017).

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 Corethrellidae as distinct from the Chaoboridae (Wood and Borkent 1989). Phylogenetic relationships among the families of Culicomorpha are well known and have considerable support (Borkent 2012, Kutty et al. 2018) but the position of Chironomidae needs further testing, as either the sister group of all remaining families, or as the sister group of Ceratopogonidae.

With 798 named species, the Chironomidae (non-biting midges) currently stand as the most species-rich family of Diptera 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 Chaoboridae (11 species in Canada), Thaumaleidae (13) and Dixidae (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 Culicidae (82 species in Canada), Simuliidae (164) and Ceratopogonidae (263) are all quite diverse, whereas a single species of Corethrellidae (formerly in Chaoboridae) is known for the country (Table 1). The Culicidae (mosquitoes) and Simuliidae (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 Ceratopogonidae (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 Culicomorpha has meant that they are some of the best known of the Diptera, including interpretation of their immatures. Taxa may be identified using the following references: Chaoboridae (Sæther 1972, larvae, pupae, adults), Corethrellidae (Borkent 2008, adults; McKeever and French 1991, larvae, pupae), Culicidae (Mattingly 1971, larvae, pupae, adults to genus; Wood et al. 1979, larvae, adults) Chironomidae (Wiederholm 1986, 1989, pupae, adults to genus; Andersen et al. 2013, larvae to genus), Ceratopogonidae (Downes and Wirth 1981, adults to genus; Borkent 2014, pupae to genus), Simuliidae (Adler et al. 2004, larvae, pupae, adults), and Thaumaleidae (Arnaud and Boussy 1994, Pivar et al. 2018, Sinclair 1996, adults). Dixidae are poorly understood and require fundamental revision (Greenwalt and Moulton 2016).

Immature Culicomorpha are aquatic in both lotic and lentic habitats where they are prey for aquatic organisms, including fish. The Chironomidae 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 Culicidae 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). Simuliidae 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 Ceratopogonidae are predaceous but the majority of Culicoides Latreille species have biting females. One species, C. sonorensis Wirth and Jones, is a vector of Bluetongue virus of cattle and other ruminants in south-central British Columbia (Sellers and Maarouf 1991). Female Corethrellidae are known only to bite frogs.

The boundaries of the Bibionomorpha have revolved around the nematocerous families included in the Neodiptera by Michelsen (1996), but there has been little consensus. Hennig (1973) favoured a broad concept that included the Bibionidae, Pachyneuridae, Sciaroidea, Scatopsoidea, Anisopodidae, Axymyiidae, and Perissommatidae (non-Nearctic), whereas Wood and Borkent (1989) restricted the infraorder to Bibionidae, Pachyneuridae, and Sciaroidea. Amorim (1993) included the following groups in the Bibionomorpha: Bibionidae, Pachyneuridae (in part), Sciaroidea, and Anisopodidae. More recently molecular analyses have again supported the broad concept sensu Hennig (1973), exclusive of Perissommatidae (Wiegmann et al. 2011) or exclusive of both Perissommatidae and Axymyiidae (Bertone et al. 2008). Grimaldi and Engel (2005) also recognized a broad concept, although exclusive of Scatopsoidea. Recently Sinclair et al. (2013) showed that the male terminalia of Perissommatidae show derived attributes of the Bibionomorpha 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 Bibionomorpha s. str. have been studied by Wood and Borkent (1989), Amorim and Rindal (2007), and Ševčík et al. (2016).

Three families are excluded from Bibionomorpha 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). Anisopodidae and Canthyloscelidae (= Synneuridae) have low diversity in Canada (six and one species, respectively) but the Scatopsidae are represented by 30 species, with 15–20 more expected (Table 1). Canadian Scatopsidae can be identified using the genus key in Cook (1981) and species keys referred to therein. The Anisopodidae have not received much recent taxonomic attention in the Nearctic, although species of Sylvicola Harris were revised by Pratt and Pratt (1980). The larvae of these families are saprophagous and found in moist decaying organic matter.

Seven of the ten families of Bibionomorpha s. str. found in Canada are species-poor, including Pachyneuridae (1 species in Canada), Bibionidae (26), Hesperinidae (1; formerly in Bibionidae), and the following four families, formerly included in Mycetophilidae by J.F. McAlpine et al. (1979): Ditomyiidae (3), Bolitophilidae (16), Keroplatidae (28) and Diadocidiidae (2) (Table 1). The number of species of Bibionidae 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 Sciaridae (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 Cecidomyiidae (243 species in Canada) have more than doubled since 1979 and those of Mycetophilidae 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 Cecidomyiidae, 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 Cecidomyiidae 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 Cecidomyiidae appears sparse, general information and identification to genera of the subfamily Cecidomyiinae are provided by Gagné (1989, 2018). The genera of Mycetophilidae can be keyed in Vockeroth (1981), but some subfamilies are now recognized as families (see above). Several genera of Mycetophilidae have been revised since 1979, including: Acomoptera Vockeroth (Kerr 2011), Leptomorphus Curtis (Borkent and Wheeler 2012), Mycomya Rondani (Väisänen 1984), Phthinia Winnertz (Fitzgerald and Kerr 2014), Sciophila Meigen (Zaitzev 1982) and Trichonta Winnertz (Gagné 1981).

Members of the Bibionomorpha 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 Cecidomyiidae 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 Cecidomyiidae are serious pests of cereals, Brassicaceae, conifers, apple trees, etc., and a zoophagous species is used in the biocontrol of aphids (Darvas et al. 2000).

This infraorder is represented by the single family Xylophagidae, although some authors have divided it into smaller family units (Woodley 1989). The Xylophagomorpha are considered the sister group to the Tabanomorpha 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 Tabanomorpha. Much of the uncertainty of higher level phylogeny of the Tabanomorpha is due to doubts concerning the limits and monophyly of the Rhagionidae. Through combined morphological and molecular analyses, Kerr (2010) redefined the family Rhagionidae, establishing its monophyly and recognizing the families Austroleptidae (Australia and Chile) and Bolbomyiidae. The classification of Kerr (2010) is followed here.

Six families of Tabanomorpha occur in Canada and these are organized in two superfamilies. In Rhagionoidea, Bolbomyiidae include three known species in Canada and two more are expected (Table 1). Rhagionidae 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 Rhagionidae 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 Bolbomyiidae are unknown.

In Tabanoidea, three families have low diversity: Pelecorhynchidae (5 species in Canada), Athericidae (2), and the recently erected monotypic family Oreoleptidae (1) (Zloty et al. 2005; Table 1). In part due to their large size and the biting habits of most females, the Tabanidae (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 Athericidae and Oreoleptidae occur in riffle zones and/or vegetation of cool streams and flowing rivers. Those of Pelecorhynchidae and Tabanidae are predators of invertebrates found mostly in wetland soils.

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

The Stratiomyidae 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 Stratiomyidae 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 (Caloparyphus James, Stratiomys Geoffroy, Odontomyia Meigen, Nemotelus Geoffroy), which could reveal a few undescribed species as well as some synonyms. Only two genera and seven species of Xylomyidae 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 Xylomyidae are found under the bark of trees but little is known of the biology of these uncommon flies.

The higher classification and phylogeny of the Asilomorpha (containing one superfamily – Asiloidea) 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 Asilomorpha, which appear paraphyletic in relation to Eremoneura (Sinclair et al. 1994, Trautwein et al. 2010), has primarily revolved around the placement of the genus Hilarimorpha Schiner, which has previously been assigned to the Bombyliidae, Therevidae, or its own separate family considered sister to the Bombyliidae, Asiloidea or Eremoneura (Trautwein et al. 2010).

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

The Canadian fauna of the larger families of Asilomorpha has received much attention since JF McAlpine et al. (1979). The number of Asilidae (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 Bombyliidae 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 Bombyliidae currently documented represent a 50% increase since 1979 and more than 40 additional species are expected in Canada (Table 1). A world catalogue of Therevidae 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 Asilomorpha display a wide range of habitats and life histories. The Scenopinidae have predaceous larvae associated with wood-boring larvae, bird’s nests, and carpet beetle larvae. The larvae of Hilarimorphidae are unknown and adults are sporadically collected, with verified records indicating that they frequent riverbanks. Adult Mythicomyiidae 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 Asilidae are efficient predators with highly modified mouthparts; the larvae live in soils and rotting wood. Larvae of Therevidae are often found burrowing through sandy soils (Irwin and Lyneborg 1981). The larvae of Mydidae and Apioceridae are predaceous in sandy soils and adults are flower feeders. The Bombyliidae are generally parasitic on various Holometabola or predaceous on egg pods of grasshoppers (Hall 1981), with adults visiting flowers.

The Empidoidea are a monophyletic lineage comprising five main families, namely Atelestidae, Brachystomatidae, Empididae, Hybotidae, Dolichopodidae s. lat. (including Microphorinae and Parathalassiinae) (Sinclair and Cumming 2006) and three previously unassigned genus-groups. Some authors have treated two of these genus-groups as separate families (i.e., Homalocnemidae (non-Nearctic) and Oreogetonidae), because of the availability of family-group names (Thompson 2009, Pape et al. 2011, Marshall 2012). The Iteaphila group has recently been elevated to subfamily rank within yet another newly recognized Empidoidea family, Ragadidae (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): Oreogetonidae (7 species), Empididae (251), Brachystomatidae (11), Hybotidae (155), and Dolichopodidae s. lat. (508), plus the Iteaphila genus-group (17). Apart from the Dolichopodidae (exclusive of Microphorinae and Parathalassiinae), the remaining groups were lumped into the Empididae in JF McAlpine et al. (1979). The current total of 949 Canadian species of Empidoidea 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 Empididae 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 Oreogetonidae and two subfamilies of Empididae (Clinocerinae and Hemerodromiinae) include species with aquatic larvae. The remaining Empididae are mainly terrestrial and many species are important pollinators (Rader et al. 2016), especially in alpine and arctic regions (Lefebvre et al. 2014). The Hybotidae are common predators in forests, grasslands and agricultural fields (Sinclair and Cumming 2017), whereas the Dolichopodidae are significant predators in various aquatic, semi-aquatic and terrestrial habitats (Grichanov and Brooks 2017).

No recent hypotheses support the monophyly of the Aschiza, which traditionally included the cyclorrhaphan families exclusive of Schizophora (or those flies without a ptilinum for exiting the puparium). Only Brown (1992, 1995) and Disney (1994) have supported the monophyletic Aschiza concept proposed by McAlpine (1989). All other morphological and molecular analyses have shown that the “Aschiza” are a grade and should be referred to as the Lower Cyclorrhapha (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 Schizophora. Unfortunately, there has been a profound lack of agreement about relationships within this grade.

The Schizophora are a large monophyletic subgroup of Cyclorrhapha 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 Acalyptratae and the monophyletic Calyptratae.

Acalyptratae are a large and heterogeneous assemblage of families circumscribed by the absence of characters used to define the Calyptratae. 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 Ephydroidea, Nerioidea, and Tephritoidea. 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.

This large monophyletic subgroup of Schizophora 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 (Muscoidea), 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 Hippoboscoidea, the paraphyletic ‘muscoid grade’, and the Oestroidea (nested in the muscoid grade) proposed by Kutty et al. (2008). The composition of the Calyptratae has remained mostly unchanged since Roback (1951), and ten of the approximately 15 recognized calyptrate families worldwide (Cerretti et al. 2017) occur in Canada.

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 Oestroidea (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 Tachinidae have a large presence in Canada (O’Hara and Wood 2004, J O'Hara and M Wood unpubl. data), placing them second behind the Chironomidae as the most speciose family of Diptera 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 Sarcophagidae (135 species in Canada) and the Calliphoridae (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 Oestridae (17 species in Canada) and introduced Rhinophoridae (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 Oestridae and, to a lesser extent, the Calliphoridae (Table 1).

The Oestroidea are generally large robust flies that display a wide range of life histories and ecological habits. The Tachinidae and Rhinophoridae are all parasitoids of terrestrial arthropods and the larvae of Oestridae are internal parasites of wild or domestic mammals. The calliphorids include a few parasitoid species in the Pollenia Robineau-Desvoidy complex, all presumably introduced from Europe with their earthworm hosts (Rognes 1991), and some ectoparasites of birds (Protocalliphora Hough) but most are saprophagous and associated with decaying animal matter. The Sarcophagidae 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 Oestridae, Sarcophagidae and Calliphoridae are also known to cause myiasis in humans and other vertebrates (Marshall 2012).