Key to families of Diptera in British Columbia

Key I: Families of DIPTERA in British Columbia

1.	Wings well-developed, extending at least to midpoint of abdomen, and of normal shape.	2
-	Wings absent or greatly reduced.	Wingless Diptera (Key VII)
2 (1).	Antennal flagellum with 4 or more flagellomeres which are usually uniform in shape and size, apical segments not modified into a stylus or arista. Palpus usually with 3-5 segments, rarely with one or two segments.	NEMATOCERA (Key II)
-	Antennal flagellum usually more compact than Nematocera, very rarely more than 8 segments, apical segments often modified into a stylus or arista those with 4 or more flagellomeres have non-uniform sized and shaped segments. Palpus never with more than 2 segments.	3
3 (2).	Ptilinal suture and lunule present.	4
	Ptilinal suture and lunule absent.	ORTHORRHAPHOUS BRACHYCERA and MUSCOMORPHA, ASCHIZA (Key III)
4(3).	Thorax usually strongly flattened, hind coxa widely separated, tarsal claws large, strongly recurved, often toothed. Adults ectoparasitic on mammals or birds.	CALYPTRATAE, HIPPOBOSCOIDEA (Key IV)
-	Thorax not overly flattened, hind coxa close together, tarsal claws small, somewhat curved, never toothed. With very few exceptions (some members of the family Carnidae) adults not ectoparasitic on mammals or birds.	5
5 (4).	Greater ampulla present as a distinct bulbous swelling below wing base and fused to the anepimeron. Vibrissae usually present. Antennal pedicel always with an entire dorsal seam.	CALYPTRATAE, OESTROIDEA and MUSCOIDEA (Key V)
-	Greater ampulla usually absent, but if present (some Tephritidae, Psilidae and Periscelididae) then the vibrissae are absent (some Milichiidae with vibrissae have a bulbous swelling – the lesser ampulla, near the wing base and the anepimeron however in these cases there is a distinct white, membranous area between the anepimeron and the lesser ampulla). Antennal pedicel usually with dorsal seam incomplete or absent.	ACALYPTRATAE (Key VI)

Key II: Key to Families of NEMATOCERA

1.	Wing with a network of delicate crease-like lines between the main veins, and with the number of main veins fully or partially reduced; anal lobe strongly projected towards the base of the wing.	2
-	Wing lacking a network of delicate crease-like lines between the main veins, number of main veins sometimes reduced; anal region of wing usually not as strongly projecting towards base of wing as above.	3
2 (1).	Antennal flagellum with 11-13 flagellomeres, apical flagellomere approximately equal in length to preceding segments; wing relatively long and narrow.	Blephariceridae
-	Antennal flagellum with 4 flagellomeres, apical segment greatly elongated in males; wing broad and fan-like.	Deuterophlebiidae
3 (1).	Halter with a basal appendage (prehalter).	Ptychopteridae
-	Halter lacking a basal appendage.	4
4 (3).	Wing with veins A₁ and A₂ reaching wing margin as distinct veins.	5
-	Wing with at least vein A₂ absent or fading out before reaching wing margin.	6
5 (4).	Vein A₂ usually more than ½ length of vein A₁ and fairly straight. Ocelli absent or greatly reduced.	Tipulidae
-	Vein A₂ usually much less than ½ length of vein A₁ and strongly curved at apex. Ocelli present, distinct.	Trichoceridae
6 (4).	Radial vein with 5 separate branches reaching the wing margin; discal cell present; anal lobe usually well developed.	Tanyderidae
-	Radial vein usually with fewer than 5 branches reaching the wing margin; if 5 separate branches reaching the margin, then discal cell absent and anal lobe poorly developed.	7
7 (6).	Costa continuing around the wing onto the hind margin (often weaker beyond wing tip), well beyond the last radial vein.	8
-	Costa ending near last branch of radial vein, near wing tip; if costal character indistinct (Pachyneuridae) then radial vein with 3 branches and a crossvein, r-r, which forms a closed cell between R₂₊₃ and R₄₊₅.	14
8 (7).	First tarsomere much shorter than second and both more or less fused giving the appearance of 4 tarsal segments.	Cecidomyiidae (in part)
-	First tarsomere longer than the second, with distinctly 5 tarsal segments.	9
9 (8).	Ocelli always absent; costa without a break beyond the insertion of R₄₊₅.	10
-	Ocelli usually present, if absent the costa has a break just beyond the insertion of R₄₊₅.	Cecidomyiidae (in part)
10 (9).	Wing with 6 or 7 veins reaching margin; antennae about as long as head, flagellum short and slender with 2 or 3 bristles at apex.	Thaumeleidae
-	Wing with 9 to 11 veins reaching margin; antennae at least twice length of head, flagellum not reduced and usually with rings of setae on all flagellomeres.	11
11 (10).	Medial vein with 3 branches; subcosta incomplete or ending in costa or R₁ before middle of wing; very setose, moth-like flies.	Psychodidae
-	Medial vein with 2 branches; subcosta complete, ending at costa at or beyond midpoint of wing; flies at most moderately setose, mosquito-like.	12
12 (11).	Flattened scales present on wing veins., head legs, and often other parts of body. Proboscis long, extending well beyond clypeus.	Culicidae
-	Scales absent from wing veins, head, legs, and other body parts although narrow setae often present. Proboscis short, at most extending to just beyond clypeus.	13
13 (12).	Wing veins with dense covering of long narrow setae; base of vein R₂₊₃ straight. Antennal flagellomeres with long setae in distinct rings.	Chaoboridae
-	Wing veins with sparse covering of very short; base of vein R₂₊₃ strongly curved forward, antennal flagellomeres with short sparse indistinctly arranged setae.	Dixidae
14 (7).	Ocelli absent.	15
-	Ocelli present.	17
15 (14).	Antennae short, about as long as head); flagellum with short setae in both sexes. Wing relatively broad with weakened posterior veins.	Simuliidae
-	Antennae long, much longer that head; flagellum with distinct long setae especially in males. Wing relatively narrow, with posterior veins usually prominent.	16
16 (15).	Medial vein almost always forked, with M₂ sometimes weakened at base, rarely faint over entire length; never more than 2 branches of the radial vein reaching the wing margin. Postnotum usually without a longitudinal groove. Females’ mouthparts usually with blade-like mandibles.	Ceratopogonidae
-	Medial vein never forked, always lacking M₂; usually with 3 branches of radial vein reaching the wing margin. Postnotum usually with a longitudinal groove. Neither sex’s mouthparts with functional mandibles.	Chironomidae
17 (14).	Wing with radial vein 3 branched and with crossvein r-r forming a closed cell between R₂₊₃ and R₄₊₅.	Pachyneuridae
-	Wing with radial vein sometimes having 3 branches, but never with crossvein r-r forming a closed cell between R₂₊₃ and R₄₊₅.	18
18 (17).	Wing with discal cell present, medial vein with 3 branches.	Anisopodidae
-	Wing lacking a discal cell, medial vein with never more than 2 branches.	19
19 (18).	Radius with 4 branches; R₂ and R₃ appearing as 2 separate veins, with R₂ short forming an oblique angle with R₃ and joining R₁ at costa; pair of shiny oval spots near middle of scutum.	Axymyiidae
-	Radius with 3 or fewer branches; R₂ and R₃ never appearing as 2 separate veins.	20
20 (19).	Wing with 2 closed basal cells – br and bm, that are separate and closed on their distal ends). Pulvilli and empodium well and equally developed; acropod with 3 similar pads.	Bibionidae
-	Wing almost always (few exceptions in the family Mycetophilidae) with only one closed basal cell -- either cells br and bm fused or with cell bm open distally. Pulvilli at most weakly developed; acropod never with 3 similar pads.	21
21 (20).	Compound eyes nearly meeting below the antennae, and holoptic above.	Canthyloscelidae
-	Compound eyes widely separated below antennae with or without a narrow eye bridge above the antennae.	22
22 (21).	Tibiae without apical spurs. Wing with costa ending well before apex of wing and usually with only costa and radial veins darkly pigmented.	Scatopsidae
-	Tibiae with apical spurs. Wing with costa ending at or near the apex of the wing and usually with all veins darkly pigmented.	23
23 (22).	Compound eyes meeting narrowly above antennae. Wing with base and forked portion of M subequal in length and with fork bell-shaped	Sciaridae
-	Compound eyes never meeting above antennae. Wing usually with fork of M much longer than base and lanceolate in shape	Mycetophilidae

Key III: Key to Families of ORTHORRHAPHOUS BRACHYCERA
and MUSCOMORPHA, ASCHIZA

1.	Empodia pulvilliform; each acropod with 3 similar shaped flattened pads below tarsal claws. Vein CuA₂ free or forming an acute angle with vein A₁ near the wing margin.	2
-	Empodia usually setiform or absent; if acropod with 3 pads them empodium much narrower and more tapered than pulvilli; if empodia somewhat pulvilliform then CuA₂ joining A₁ at an obtuse angle far from the wing margin.	13
2 (1).	Head unusually small, rarely exceeding ½ width of thorax; compound eyes of both sexes nearly, to entirely, holoptic. Lower calypter extremely large, wider than head.	Acroceridae
-	Head more than ½ width of thorax; compound eyes never holoptic in females. Lower calypter smaller, not as wide as head.	3
3 (2).	Branches of radius and medial veins converging towards wing apex; branches of medial vein curved forward and ending near apex of wing, and with a diagonal vein running from distal end of cell br to posterior margin of wing.	Nemestrinidae
-	Branches of radius and medial vein diverging to wing apex; branches of medial vein meeting wing margin behind apex and lacking a diagonal vein.	4
4 (3).	Costa ending near wing apex.	5
-	Costa continuing beyond wing apex, usually weaker along posterior margin of wing.	7
5 (4).	Costa usually ending well before, rarely nearly at, wing apex; branches of R more or less crowded anteriorly, and all ending in margin well before wing apex; cell d short, usually little longer than wide. Tibial spurs usually absent.	Stratiomyidae (in part)
-	Costa extending to wing apex or slightly beyond; branches of R not crowded anteriorly, with R₅ ending at or beyond wing apex; cell d at least two times as long as broad. Tibial spurs present on at least middle and hind tibiae.	6
6 (5).	Fore tibia with a ventral apical spur.	Xylophagidae (in part)
-	Fore tibia without a ventral apical spur.	Xylomyidae
7 (4).	Scutellum always setulose and with 4 prominent spines on margin.	Stratiomyidae (in part)
-	Scutellum sometimes setulose, but never with 4 prominent spines	8
8 (7).	Subscutellum strongly developed; posterior thoracic spiracle with a scale-like elevation immediately behind it.	9
-	Subscutellum absent or poorly developed.	12
9 (8).	Antennal flagellum with a slender non-annulated arista. Wing with cell r₁ closed by vein R₂₊₃ meeting costa at end of R₁.	Athericidae
-	Antennal flagellum with a coarse annulated stylus.	10
10 (9).	Both upper and lower calypteres large, subequal in size. First abdominal tergite deeply notched in the middle of the posterior margin, and with a median suture.	Tabanidae
-	Upper calypter moderately large, lower one scarcely developed. First abdominal tergite without a median notch or suture.	11
11 (10).	Proscutellum (a small swelling between the scutellum and the mesonotum) present; aedeagal tines of male terminalia absent; female with a well developed postabdomen, clearly separated from the preabdomen.	Pelecorhynchidae
-	Proscutellum absent; aedeagal tines of male terminalia present; female with postabdomen not clearly separated from preabdomen.	Oreoleptidae
12 (8).	Clypeus exposed and strongly convex, in profile with anterior surface bulging beyond parafacial, and usually reaching dorsally to bases of antennae. Flagellum usually with not more than 7 flagellomeres, and with distal ones frequently forming a slender stylus or arista.	Rhagionidae
-	Clypeus recessed in a deep facial groove and more or less flattened, in profile with anterior surface depressed below level of parafacial, and not reaching dorsally to bases of antennae. Flagellum usually with at least eight gradually smaller flagellomeres, and with apical ones not forming a slender stylus or arista except in the genus Dialysis.	Xylophagidae (in part)
13 (1).	CuA₂ reaching wing margin near A₁ or joining A₁ near wing margin; if joining A₁, then CuA₂ at least 1.5 times longer than apical section of A₁, except in a few Bombyliidae.	14
-	CuA₂ absent or vestigial, or joining A₁ far from wing margin; if joining A₁, then CuA₂ at most scarcely longer than apical section of A₁, except in a few Empididae and a few Platypezidae.	21
14 (13).	Branches of M peculiarly curved forward, more or less parallel to posterior wing margin at least M₁ ending freely in wing margin before wing apex.	15
-	Branches of M not curved as above, but if somewhat bent forward then not ending freely in wing margin.	16
15 (14).	Flagellum unusually long with a slender stalk-like base and strongly clubbed apex; stalk at least twice as long as combined length of scape and pedicel. Only one ocellus present.	Mydidae
-	Flagellum shorter than head, without a stalk-like base; entire flagellum not much longer than combined length of scape and pedicel. Three ocelli present.	Apioceridae
16 (14).	Spurious vein evident as a strong vein-like fold between Rs and M; M₁ curved forward roughly in line with crossvein dm-cu and joining unbranched R₄₊₅ in a crossvein-like manner.	Syrphidae
-	Spurious vein undeveloped; M₁ usually not curved forward in a crossvein-like manner, but if curved forward then joining a furcated R₄₊₅.	17
17 (16).	Head strongly hemispherical, with compound eyes abnormally large and almost meeting both above and below antennae. Flagellum with a dorsal arista. R₄₊₅ is unbranched; costa ends at wing apex.	Pipunculidae
-	Head usually not hemispherical, but if so then flagellum without a dorsal arista. R₄₊₅ usually furcated: costa usually continuing around wing.	18
18 (17).	Vertex usually distinctly excavated between eyes; ocellar tubercle below dorsal level of compound eyes; compound eyes never holoptic. Face relatively long, with a cluster or row of long bristles, the mystax. Proboscis stout, polished; labella reduced and inconspicuous; hypopharynx protrusible, strongly developed for piercing.	Asilidae
-	Vertex not or only slightly concave; ocellar tubercle usually elevated above the dorsal level of the compound eyes; compound eyes usually holoptic in males. Face relatively short, sometimes setulose, but without a mystax. Proboscis short and stout to long and thin, usually dull pruinose; labella usually well-developed and conspicuous; hypopharynx not protrusible, not developed for piercing.	19
19 (18).	Wing with cell bm truncate distally and with four corners from which arise four separate veins (M₁₊₂, M₃, CuA₁, CuA₂) base of cell m₃ truncate.	Therevidae
-	Wing with cell bm, when present, pointed distally and with three corners from which arise three separate veins (M₁₊₂, M₃+CuA₁ and CuA₂); base of cell m₃, when present, pointed.	20
20 (19).	Wing with cell dm absent, and with R₄₊₅ and M₁₊₂ rather similarly forked, each fork not longer than its base.	Hilarimorphidae
-	Wing with cell dm usually present, but if not the R₄₊₅ and M₁₊₂ not similarly forked.	Bombyliidae
21 (13).	Antennal flagellum with a minute stylus concealed in a subapical pit. Crossvein r-m at or beyond middle of wing; M unbranched and curved forwards, joining R₄₊₅ or closely approaching it in the wing margin.	Scenopinidae
-	Antennal flagellum with an elongate, fully exposed stylus or arista. Crossvein r-m well before middle of wing or absent; M branched or unbranched, sometimes curved forward, but not as above.	22
22 (21).	Wing pointed at apex with peculiar linear venation; main veins except subcosta and R₃ with black setulae above. Antennal flagellum rounded, with a terminal arista. Slender brownish or yellowish flies, 2-5 mm long.	Lonchopteridae
-	Wing rounded at apex, and with radiating venation; veins at least in posterior half of wing not setose. Antennal flagellum, body size, and colour variable.	23
23 (22).	Wing with branches of R strongly thickened and crowded into anterior base, and with four other weak and peculiarly aligned veins in remainder of wing blade; costa ending near middle of anterior margin.	Phoridae
-	Wing with branches of R not strongly thickened and crowded anterobasally, and with other veins normal; costa extending at least to wing apex.	24
24 (23).	Antenna with pedicel much longer than flagellum; flagellum with a dorsal three-segmented arista. Mid coxal prong strongly developed.	SCHIZOPHORA (exception lacking a ptilinal suture) Sciomyzidae: genus Sepodon
-	Antenna with pedicel not or scarcely as long as flagellum; if arista three-segmented, then terminally situated. Mid coxal prong absent.	25
25 (24).	Wing with both A₁ and subcosta reaching wing margin, and with cell cup acute at posterior apex. Hind tarsus, at least in male, with one or more basal tarsomeres expanded and flattened. Arista three-segmented, terminally situated.	Platypezidae
-	Wing rarely with A₁ reaching wing margin, but if so either subcosta incomplete or cell cup obtuse or rounded at posterior apex. Hind tarsus not modified as above. Arista or stylus two-segmented, terminally or dorsally situated.	26
26 (25).	R_s originating at or near level of crossvein h, distal to crossvein h by, at most, length of crossvein h; crossvein r-m in basal fourth of wing; cells bm and dm confluent, that is, crossvein bm-cu absent; subcosta usually abruptly curved posteriorly and fused with R₁, except in the subfamily Hydrophorinae.	Dolichopodidae
-	R_s originating well distal to level of crossvein h, usually distal to it by more than length of crossvein h; crossvein r-m distal to basal fourth of wing; cell bm usually separated from cell dm (when cell dm is present) by crossvein bm-cu; subcosta usually joining costa or ending freely, never abruptly joining R₁.	Empididae

Key IV: Key to Families of HIPPOBOSCOIDEA

1.	Compound eyes large, horizontally oval, at least ¾ as high as head, with at least 100 very small facets. Posterior wing veins weaker than anterior veins. Ectoparasitic on birds and mammals except bats.	Hippoboscidae
-	Compound eyes, if present, small, round, never more that ½ as high as head, and with less than 40 relatively large bead-like facets. Wing veins relatively uniform in strength. Ectoparasitic on bats.	Streblidae

Key V: Key to Families of OESTROIDEA and MUSCOIDEA

1.	Large (9-25 mm long) heavy-bodied, finely setulose flies which lack large setae and resembling honeybees, bumblebees or carpenter bees. Head bulbous with greatly reduced or atrophied mouthparts, no vibrissae, and small recessed antennae. Meron usually with a cluster of long setae. All larvae obligate parasites of mammals.	Oestridae
-	Usually smaller (1-15mm long) normally setose flies. Head usually with well-developed mouthparts, vibrissae, and normal-sized antennae. Meron bare or with a row of bristles, sometimes with additional scattered fine setulae. Larvae rarely parasites of mammals.	2
2 (1).	Meron bare.	8
-	Meron with a row of bristles, sometimes with additional scattered fine setulae.	3
3 (2).	Subscutellum strongly developed.	Tachinidae
-	Subscutellum absent or weakly developed.	4
4 (3).	Abdomen and usually thorax with a distinct metallic blue or green sheen. Palpus usually orange-yellow.	Calliphoridae (in part)
-	Abdomen usually mostly dull, variegated gray, brown or black, sometimes shiny black, but never metallic blue or green. Palpus blackish to yellowish.	5
5 (4).	Thorax with silky wavy yellowish setulae as well as normal black bristles and setulae.	Calliphoridae (in part)
-	Thorax without silky yellowish setulae.	6
6 (5).	Scutum usually with three conspicuous black stripes on a gray background. Notopleuron usually with 3 or 4 bristles. Hind coxa usually with setulae on posterior surface. Arista usually plumose.	Sarcophagidae (in part)
-	Scutum with or without black stripes. Notopleuron always with only 2 bristles. Hind coxa always without setulae on posterior surface. Arista plumose to bare.	7
7 (6).	Coxopleural streak present.	Sarcophagidae (in part)
-	Coxopleural streak absent.	Calliphoridae (in part)
8 (2).	A₂ curved forward beyond tip of A₁, with course of A₁ (if extended) intersecting A₂ before wing margin; subcosta always nearly straight on apical 2/3. Hind tibia always with a strong bristle near middle of dorsal surface as well as a preapical dorsal bristle.	Muscidae (Subfamily Fanninae)
-	A₂ not curved forward beyond tip of A₁, with course of A₁ not intersecting A₂ before wing margin; subcosta usually distinctly curved forward on apical half or less. Hind tibia rarely with a strong bristle near middle of dorsal surface as well as a preapical dorsal bristle (sometimes a similar bristle- the calcar, present on posterodorsal surface).	9
9 (8).	Palpus absent. Crossveins r-m and dm-cu separated by a distance not or scarcely greater than length of crossvein dm-cu; crossvein bm-cu partially atrophied.	Anthomyiidae (in part)
-	Palpus present. Crossveins r-m and dm-cu usually more widely separated; crossvein bm-cu usually complete.	10
10 (9).	A₁ never reaching wing margin even as a fold; lower calypter broad, never linear.	Muscidae (in part)
-	A₁ usually reaching wing margin at least as a fold. if not then lower calypter linear.	11
11 (10).	Scutellum usually with fine pale setae on apicoventral surface; frons usually narrower in male than in female; if scutellum bare on apicoventral surface and frons wide in male then frons with strong interfrontal bristles. Occiput never with fine pale setulae, only with black bristles and setulae. Katepisternum usually with 2 to 4 bristles; lower calypter linear to broad.	Anthomyiidae (in part)
-	Scutellum bare on ventral surface; frons wide in both sexes and lacking interfrontal bristles. Occiput usually with numerous fine pale setulae, sometimes between black bristles and setulae. Katepisternum usually with 1 bristle. Lower calypter always linear.	Scathophagidae

Key VI: Key to Families of ACALYPTRATAE in British Columbia

1.	Proboscis usually very long and slender, frequently 2 or more times longer than head; pedicel usually longer than first flagellomere. Crossvein sc-r present or cell cup distinctly longer than cell bm, or with both characters present simultaneously; M joining R₄₊₅ or closely approaching it.	Conopidae
-	Proboscis usually shorter and stouter, not longer than head except in some Milichiidae and Chloropidae where it is elbowed; pedicel usually shorter than first flagellomere, but if longer then crossvein sc-r absent and cell cup shorter than cell bm; M approaching R₄₊₅ or not.	2
2 (1).	Ocelli and mid coxal prong absent; medium to large flies with heavily marked wings.	Pyrgotidae
-	Ocelli usually present; if absent, mid coxal prong present; size variable, wings marked or unmarked.	3
3 (2).	Hind tarsus with first tarsomere distinctly swollen and usually shorter than second tarsomere. Subcosta always incomplete; CuA₁ usually incomplete.	Sphaeroceridae
-	Hind tarsus with first tarsomere not swollen and longer than second tarsomere. Subcosta complete or incomplete; CuA₁ usually complete.	4
4 (3).	Subcosta abruptly bent forward at almost 90⁰, weakened beyond the bend and ending at subcostal break; wing almost always with markings. Pedicel with a dorsal cleft. Vibrissae absent. Greater ampulla usually weakly distinguishable and anepimeron always with bristles or setulae or both.	Tephritidae
-	Subcosta less abruptly bent. Not agreeing with one or more of the remaining characters.	5
5 (4).	Slender bodied flies with long slender legs. R₄₊₅ and M meeting or strongly converging at wing margin; subcosta always complete.	6
-	Usually stouter flies with shorter heavier legs. R₄₊₅ and M usually subparallel or divergent at wing margin; subcosta complete or incomplete.	7
6 (5).	Eyes very large, distinctly higher than long, and closer together in male than female. Ocellar bristles present. R₁ setose above. Katepisternum evenly pilose, but without large bristles.	Tanypezidae
-	Eyes smaller than above, not much higher than long, and equidistant in both sexes. Ocellar bristles absent. R₁ not setose. Katepisternum never evenly pilose, always with one or more large bristles.	Micropezidae
7 (5).	Subcosta complete or nearly so, ending at costa or just short of it and free from R₁ distally.	8
-	Subcosta incomplete, not reaching costa, often fusing with R₁ distally.	29
8 (7).	Costa without a subcostal break.	9
-	Costa with a subcostal break.	18
9 (8).	Posterior thoracic spiracle with one or more fine bristles on lower margin. Form usually ant-like; head subspherical; palpus usually vestigial; abdomen usually elongate and basally constricted.	Sepsidae
-	Posterior thoracic spiracle without bristles or outstanding setulae. Form usually not ant-like; palpus usually well-developed.	10
10 (9).	Metepisternum setose below posterior thoracic spiracle; thorax distinctly flattened. Squatty and strongly bristled flies.	Coelopidae
-	Metepisternum bare; thorax not very flattened. Form and bristling variable.	11
11 (10).	Face broadly membranous and sunken in middle; vibrissa present.	12
-	Face uniformly sclerotized and convex in middle; vibrissa absent.	13
12 (11).	Arista subapical; frons with a pair of cruciate interfrontal bristles. Costa without humeral break. All tibiae with a preapical dorsal bristle.	Clusiidae (in part)
-	Arista dorsobasal. Frons without cruciate interfrontal bristles. Costa with humeral break. All tibiae without a preapical dorsal bristle.	Acartophthalmidae
13 (11).	Some or all tibiae with a preapical dorsal bristle.	14
-	All tibiae without a preapical dorsal bristle.	16
14 (13).	Postocellar bristles distinctly convergent.	Lauxaniidae
-	Postocellar bristles almost parallel, divergent, or absent.	15
15 (14).	Clypeus large and prominent, in profile distinctly bulging beyond lower margin of face. Pedicel always short.	Dryomyzidae
-	Clypeus small and withdrawn, in profile more or less concealed under lower margin of face. Pedicel usually elongate.	Sciomyzidae
16 (13).	Postocellar bristles convergent or absent. Clypeus small and withdrawn. Female with a flexible tubular ovipositor.	Chamaemyiidae (in part)
-	Postocellar bristles divergent or absent. Clypeus large and prominent. Female with rigid shaft-like ovipositor.	17
17 (16).	Postocellar bristles distinctly developed, divergent. Katepisternal bristle present.	Otitidae (in part)
-	Postocellar bristles absent or very weakly developed. Katepisternal bristles absent, though setulae or pile commonly present.	Platystomatidae
18 (8).	Vibrissae present, but sometimes weak in the family Tethinidae.	19
-	Vibrissae absent, but subvibrissal bristles sometimes vibrissae-like.	26
19 (18).	Costa with a distinct humeral break as well as a subcostal break.	20
-	Costa without a humeral humeral break, with a subcostal break only.	21
20 (19).	Gena broad, with a row of bristles in the middle. Proboscis with a stout bulbous prementum and short inconspicuous labella.	Carnidae (in part)
-	Gena usually narrow, but if broad then bristles confined to lower margin. Proboscis with slender prementum and long conspicuous labels folded back along prementum.	Milichiidae (in part)
21 (19).	Pedicel with an angular though sometimes weak projection on outer side. Arista subapical. Frons with 2 to 5 strong more or less equally spaced mostly reclinate fronto-orbital bristles, with at most only the lowest one inclinate.	Clusiidae (in part)
-	Pedicel without an angular projection. Arista dorsobasal. Frons usually with fewer more or less equally spaced fronto-orbital bristles, but if with 2-5 (Agromyzidae and some Otitidae), then 2-3 of the lower ones are strongly inclinate.	22
22 (21).	Postocellar bristles divergent.	23
-	Postocellar bristles convergent or absent.	24
23 (22).	Frons always with 3-5 strong inclinate frontal bristles that are relatively similar to the two reclinate orbital bristles in size and spacing.	Agromyzidae (in part)
-	Frons seldom with any strong inclinate frontal bristles, but if one or two present then these positioned distant from and inclined oppositely to the two lateroclinate orbital bristles.	Piophilidae
24 (22).	All tibiae without a preapical dorsal bristle. Costa not spinose; A₁ fading out on apical third or more, never traceable to wing margin. Vibrissae and postocellar bristles weakly differentiated to virtually absent.	Tethinidae (in part)
-	All tibiae with a preapical dorsal bristle. Costa spinose, except in some Heleomyzidae in which A₁ is traceable to wing margin. Vibrissae and postocellar bristles strong.	25
25 (24).	Ocellar bristles arising on ocellar triangle above anterior ocellus.	Heleomyzidae
-	Ocellar bristles arising just outside ocellar triangle beside or slightly below anterior ocellus.	Trixoscelididae
26 (18).	Halter black. Anepisternum with a row of strong bristles posteriorly. Frons, face, thorax, abdomen, and legs (excluding tarsi) black, usually with metallic reflections. Stout bristly flies with broad flat abdomen; female with lance-like ovipositor.	Lonchaeidae
-	Halter usually whitish, but if halter blackish, then anepisternum without a row of strong bristles, and/or head, thorax, abdomen, and legs not as extensively black. Form variable.	27
27 (26).	Postocellar bristles convergent.	Chyromyidae (in part)
-	Postocellar bristles divergent or absent.	28
28 (27).	Scutum with one or more presutural dorsocentral bristles. Cell cup without an angular extension at posterior apex. Disc of proepisternum always bare.	Pallopteridae
-	Scutum usually without presutural dorsocentral bristles, but if present then cell cup with an angular extension at posterior apex or disc of proepisternum setose, or both.	Otitidae (in part)
29 (7).	Costa without subcostal or humeral break.	30
-	Costa with at least a subcostal break present.	32
30 (29).	CuA₂ and A₁ strong; cell cup complete. Arista bare or micropubescent.	Chamaemyiidae (in part)
-	CuA₂ and A₁ atrophied; cell cup incomplete or absent. Arista bare to plumose.	31
31 (30).	R₁ joining costa in basal third of wing; R₄₊₅ and M distinctly convergent distally. Postocellar setae weak or absent.	Asteiidae
-	R₁ joining costa near middle of wing; R₄₊₅ and M not convergent. Postocellar setae strong.	Periscelididae
32 (29).	CuA₂ and A₁ absent or vestigial, never forming a closed cell cup; crossvein bm-cu absent, making cells bm and dm confluent.	33
-	CuA₂ and A₁ present, always forming a closed cell cup; crossvein bm-cu usually present, making cells bm and dm usually separate.	35
33 (32).	Costa with a subcostal break only, without a humeral break; CuA₁ usually with a kink marking the position of atrophied crossvein bm-cu. Arista bare or micropubescent, never plumose.	Chloropidae
-	Costa with both a subcostal and a humeral break; CuA₁ without a kink. Arista bare to long plumose.	34
34 (33).	Face strongly convex; subcranial cavity usually very large. Postocellar bristles absent; pseudopostocellar bristles, if present, divergent.	Ephydridae
-	Face concave; subcranial cavity normal. Postocellar bristles present, convergent or subparallel.	Carnidae (in part)
35 (32).	Katepisternum without an outstanding bristle, though frequently setulose (Figs. 4.106-107). Vibrissae absent and gena without a vibrissa-like bristle.	36
-	Katepisternum always has one or more enlarged bristles. Vibrissae present or absent; gena with or without a vibrissa-like bristle.	37
36 (35).	Notopleuron usually with two bristles; anepisternum with an enlarged bristle, in addition to fine setulae. Ocelli situated far forward, with the anterior one about midway between the vertex and antennae.	Strongylophthalmyiidae
-	Notopleuron with one bristle, the posterior one; anepisternum without a bristle, with fine setulae only. Ocelli situated near vertex, with the anterior one on dorsal third of frons.	Psilidae
37 (35).	Costa with both a humeral and a subcostal break.	38
-	Costa without a humeral break, with a subcostal break only.	41
38 (37).	Long axis of antenna strongly elbowed, with flagellum distinctly decumbent; arista frequently long plumose.	38
-	Long axis of antenna nearly straight, with flagellum more or less porrect. Arista bare or shortly pubescent.	40
39 (38).	Costa with small evenly spaced erect spinules beyond subcostal break. Proclinate orbital bristle arising dorsolaterally to lowermost reclinate orbital bristle.	Diastatidae
-	Costa without erect spinules, with ordinary reclinate setulae only. Proclinate orbital bristle usually arising ventromedially to reclinate orbital bristle; if arising above reclinate orbital bristle then dorsomedially to it.	Drosophilidae
40 (38).	Gena broad, with a row of bristles in middle. Proboscis with stout bulbous prementum and short inconspicuous labella.	Carnidae (in part)
-	Gena usually narrow, but if broad, then bristles confined to lower margin. Proboscis with slender prementum and long conspicuous labella folded back along prementum.	Milichiidae (in part)
41 (37).	All tibiae with a preapical dorsal bristle. Frons with two reclinate orbital bristles above and one inclinate frontal bristle below.	Odiniidae
-	All tibiae without a preapical dorsal bristle. Fronto-orbital bristles not as above.	42
42 (41).	Anepimeron setulose. Frons with a single orbital bristle.	Opomyzidae
-	Anepimeron usually bare, but if setulose, then frons with more than one orbital bristle.	43
43 (42).	Postocellar bristles always present and divergent.	Agromyzidae (in part)
-	Postocellar bristles convergent or absent (there are a pair of pseudopostocellar setulae are present in some Tethinidae and are easy to confuse with true postocellars which are absent in all Tethinidae).	44
44 (43).	Anepisternum bare. Fore femur usually with a strongly developed ctenidial spine.	Anthomyzidae
-	Anepisternum setulose. Fore femur usually without a distinct ctenidial spine.	45
45 (44).	Proepisternal and proepimeral bristles present.	Tethinidae (in part)
-	Proepisternal bristle always absent; proepimeral bristle absent; except in some Aphaniosoma.	Chyromyidae (in part)

Key VII: Key to Families of Wingless Diptera in British Columbia

1.	Antennal flagellum with two or more distinctly separate flagellomeres, exclusive of stylus or arista.	2
-	Flagellum with a single consolidated segment, exclusive of stylus or arista.	8
2 (1).	Ocelli absent.	3
-	At least one ocellus present.	5
3 (2).	Mesoscutum with a complete V-shaped suture.	Tipulidae (in part)
-	Mesoscutum without a complete V-shaped suture.	4
4 (3).	Compound eye minute, reduced to one facet.	Cecidomyiidae (in part)
-	Compound eye large, multifaceted.	Tipulidae (in part)
5 (2).	Tibiae without apical spurs.	Cecidomyiidae (in part)
-	Tibiae with apical spurs, although sometimes very short.	6
6 (5).	Eye bridge present.	Sciaridae (in part)
-	Eye bridge absent.	7
7 (6).	Palpus one-segmented. Body about 2 mm long.	Sciaridae (in part)
-	Palpus with three or more segments. Body at least 4 mm long.	Mycetophilidae
8 (1).	Antennal pedicel swollen; flagellum at least twice as long as broad and with a minute apical setae. Remnant of larval eye strongly apparent. Abdomen about three times as long as remainder of body.	Chironomidae
-	Antennal pedicel not swollen; flagellum less than twice as long as broad and usually with an elongate stylus or arista. Remnant of larval eye not apparent. Abdomen less than twice as long as remainder of body.	9
9 (8).	Middle and hind coxae widely separated ventromedially; tarsal claws strongly recurved and toothed. Ectoparasites of bats, birds or mammals.	10
-	Coxae not widely separated ventromedially; tarsal claws simple. Usually not ectoparasites of bats or mammals, sometimes associated with nesting birds.	12
10 (9).	Head vertically oriented, folded back into groove on mesoscutum. First tarsomere of each tarsus very elongate, at least as long as remainder of tarsus. Ectoparasites of bats.	Nycteribiidae
-	Head horizontally oriented, not folded back. First tarsomere of each tarsus short, subequal to second tarsomere. Parasites of bats, birds or mammals.	11
11 (10).	Compound eyes always present, large, horizontally oval, at least ¾ as high as head, with at least 100 very small facets. Ectoparasitic on birds and mammals except bats.	Hippoboscidae
-	Compound eyes sometimes absent, if present, small, round, never more than ½ as high as head, and with less than 40 relatively large bead-like facets. Ectoparasitic on bats.	Streblidae
12 (9).	Lunule absent.	13
-	Lunule present.	15
13 (12).	Arista with 3 aristomeres.	Phoridae
-	Arista with 2 aristomeres.	14
14 (13).	Proboscis short and retracted. Vertex excavated. Compound eye pubescent.	Dolichopodidae
-	Proboscis elongate and projecting. Vertex convex. Compound eye bare.	Empididae
15 (12).	First tarsomere of hindleg swollen, shorter than second tarsomere.	Sphaeroceridae
-	First tarsomere of hindleg not swollen, longer than second tarsomere.	16
16 (15).	Propleuron with a vertical ridge.	Chloropidae
-	Propleuron without a vertical ridge.	17
17 (16).	Face strongly convex; subcranial cavity unusually large.	Ephydridae
-	Face concave; subcranial cavity normal.	18
18 (17).	Postocellar bristles absent; frons with a single reclinate orbital bristle. Reduced wing with an apical spot.	Opomyzidae
-	Postocellar bristles present; frons with at least two orbital bristles. Reduced wing, if present, without an apical spot.	19
19 (18).	Postocellar bristles subparallel; gena with a row of strong bristles in middle. Associated with nesting birds.	Carnidae
-	Postocellar bristles convergent; gena without a row of strong bristles in middle. Not associated with nesting birds.	20
20 (19).	All tibiae without a preapical dorsal bristle; fore femur with a strong ctenidial bristles. Frons with two strong reclinate fronto-orbital bristles on lower half.	Anthomyzidae
-	Some or all tibiae with a preapical dorsal bristle; fore femur without a ctenidial bristle. Frons without strong fronto-orbital bristles on lower half.	21
21 (20).	Frons with a proclinate orbital bristle. Arista plumose.	Drosophilidae
-	Frons without a proclinate fronto-orbital bristle. Arista bare or micropubscent.	Heleomyzidae