Calyxochaetus Bigot
Creators: name: Runyon, Justin B.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Dolichopodidae
Calyxochaetus

description: Calyxochaetus Bigot
Calyxochaetus Bigot 1888a: xxiv [1888b: xxiv]. Type species: Sympycnus nodatus Loew, by original designation [as “ Sympicnus notatus ”]. Note: Bigot (1888b) has often been cited as the first validation, but Bigot (1888a) was published a few months earlier (Evenhuis & Pont 2004).
Nothosympycnus Wheeler 1899: 51. Type species: Nothosympycnus vegetus Wheeler, designated by Coquillett 1910: 576.
Notosympycnus, error or unjustified emendation listed in Foote et al. (1965).
Diagnosis. Males of Calyxochaetus, except C. angustipennis (Aldrich), C. longitarsus sp. nov. and C. tripilus (Van Duzee), can be recognized by having the scutellum bare except for one pair of large marginal setae (Fig. 5) and foreleg with short tarsomere 1 that is less than or equal to the length of tarsomere 2 (usually very short) (Figs 39–44, 82–86, 97, 98, 116–119). Females of all species, except C. angustipennis and C. tripilus (and perhaps C. longitarsus sp. nov. whose female is unknown), are distinguished from other sympycnines by the combination of having the scutellum bare except for one pair of large marginal setae (as in Fig. 5) and the proepimeron with one or more small white hairs (Fig. 6). Males and females of C. angustipennis, C. longitarsus sp. nov. and C. tripilus can be recognized by the combination of a scutellum bare except for one pair of large marginal setae and a glabrous, shiny frons (Fig. 18). About half of Calyxochaetus species have a glabrous, shiny frons which will further distinguish males and females from similar sympycnine genera (e.g., Erebomyia Runyon & Hurley, Parasyntormon, Neoparentia Robinson, and Sympycnus).
The form of the aedeagus is a key synapomorphy shared by males of Calyxochaetus. In all species, the aedeagus (tubular, sclerotized) is separate from a broader aedeagal sheath (Figs 9–11). In other dolichopodids, the aedeagus and sheath are fused into a single structure, the phallus (Sinclair & Cumming 2006). The reversion to a separated aedeagus and sheath appears to involve only one sheath since the aedeagus remains enclosed by a second smaller sheath that sometimes separates subapically (Fig. 11).
Redescription. Male. Wing length 1.9–3.6 mm. Head: Frons wide, partly to wholly brown pruinose, about half of the species with glabrous shiny blue-violet spot on either side of ocellar tubercle (Figs 6, 18). Ocellar tubercle brown pruinose with pair of strong divergent ocellar setae and pair of very small postocellar setae. Vertex with pair of strong proclinate vertical setae and pair of postvertical setae near vertex, slightly out of line with and usually slightly larger than postocular setae. Eyes with ommatrichia; ommatidia enlarged near face and clypeus. Face narrowed below, usually distinct to mouth (eyes contiguous in two species of fortunatus group); white, silver, gray, or brown pruinose; clypeus discernible, recessed, narrow, concolorous with face. Postocular setae in single row, white with uppermost few setae becoming pale brown to black. Antenna (Figs 15–17, 26–38, 77–81, 95, 96, 104– 115) dark brown to black, sometimes with scape and pedicel yellow-brown or partly yellow; scape usually laterally flattened and rather long, without setae; pedicel short, conical, with ring of black subapical setulae, never projecting thumb-like into postpedicel; postpedicel rather large, laterally flattened, usually ovate, never short triangular or sharply pointed, pubescent with microtrichia; arista-like stylus dorsobasal, black, usually (29 of 36 species) variously thickened and/or with apical lamella; article 1 rather long, usually extending to or beyond apex of postpedicel. Palpus small, oval, varying in color from white to black, usually paler apically, with small pale hairs and sometimes a few small brown to black setae. Proboscis small, brown to yellow-brown, with sparse brown hairs, each labellar lobe with 6 geminately sclerotized pseudotracheae. Thorax: Scutum and scutellum (Figs 1, 5) with thick brown pruinosity, often with weak green to blue-violet metallic reflections; scutellum sometimes with basomedial blue-violet reflections when viewed from above or behind (Fig. 5). Setae black. Mesoscutum flattened immediately anteriad of scutellum (flattened area subequal in size to scutellum). Pleura dark brown with gray pruinosity and often weak blue reflections, sometimes partly yellow. Proepisternum ventrally with 2 (rarely 3) small, white setae. Postpronotal lobe with 1 large seta and 0–2 small to very small setae. Proepimeron, anepimeron and metepimeron bare. Acrostichal setae uniseriate (often with anteriormost few pairs becoming irregularly biseriate). Setae arranged on each side with: 6 dorsocentrals, posteriormost dorsocentral pair widely separated; 3 intra-alar (seta at notopleural suture smallest); 2 supra-alar; 2 strong notopleural; 1 strong postalar; anterior scutum in front of dorsocentral, intra-alar and supra-alar rows with additional small setulae. Scutellum (Fig. 5) with posterior margin rounded, with 1 pair of strong marginal setae, without additional hairs. Legs: Mostly yellow, coxae and hind femora often partly brownish, tarsi becoming brown apically, hind tarsus usually mostly to wholly brown. Setae mostly black except those on fore coxa yellow, anterior surface of mid and hind coxae usually yellow, and specialized setae/hairs of femora, tibiae and tarsomeres often yellow or white. Tarsal claws, pulvilli and empodium very small and similar in size on all legs, never enlarged. Foreleg: Coxa mostly to wholly yellow (rarely fuscous), anterior surface with moderately dense yellow setae and about 6 larger yellow to yellow-brown setae along apical margin. Trochanter small, bare. Femur slender, usually wholly yellow (rarely brown basally), with weak posteroventral preapical seta. Tibia yellow, usually slender, sometimes swollen (Figs 82–86), without distinct setae, but sometimes with very small dorsal seta near 1/3, never with distinct anterodorsal row of small setae on distal half, apex with anterior comb-like row of close-set yellow setulae. Tarsus longer than tibia. Tarsomere 1 almost always very short and nearly round (as in Fig. 41), rarely short cylindrical (Figs 97, 98), longer than tarsomere 2 only in C. longitarsus sp. nov. and C. tripilus (Figs 20, 22). Tarsomeres 2–5 often modified with small setae and/or dorsal microsetulae, usually slender, rarely modified in shape. Midleg: Coxa with setae on distal half of anterior surface, with black (rarely yellow-brown) anterodorsal seta near 1/2.Trochanter small with small anterior seta.Femur slender,yellow,with distinct anterior and posteroventral preapical seta, sometimes with row of longer ventral setae. Tibia slender, yellow, with anterodorsal seta near 1/5 and 1/2, a posterodorsal seta from 1/5 to 1/3, sometimes with 1 to a row of several short posteroventral setae on distal half, with about 5 setae encircling apex, rarely with ventral row of specialized setae. Tarsus (Figs 21, 45–49, 87, 99–101, 120–131) modified in all species except C. longitarsus sp. nov. (Fig. 23), usually with at least a few longer anterior hairs or slender setae, tarsomeres 2–4 often modified in shape and width. Hindleg: Coxa with black (rarely yellow-brown) seta near 1/2 on outer surface, with 1 anteromedial seta at apex, otherwise bare. Trochanter with very small anterodorsal seta, small posterior seta, usually with 1–3 small ventral setulae at base. Femur broader than mid femur, mostly yellow and usually brownish apically, with distinct anterior preapical seta, sometimes with posterior preapical seta, with small anteroventral and posteroventral preapical seta, sometimes with specialized ventral setae (Figs 50, 51, 53). Tibia thicker than mid tibia, usually slightly enlarged apically, with anterodorsal seta between 1/5 and 1/3 and between 1/2 and 3/5, posterodorsally with row of slightly longer setae of varying lengths of which 3–6 equal to or longer than tibia width, ventrally usually with row of inconspicuous setae (less than width of tibia) that are sometimes slender and/or longer near base (Figs 132–136), with about 5 setae encircling apex. Tarsus unmodified, tarsomere 1 shorter than tarsomere 2 (subequal in C. pennarista), tarsomeres 2–5 decreasing in length apically. Wing (Figs 19, 56–63, 88–91, 137, 138): Hyaline or with slight brown tinge (sometimes only anteriorly), with brown veins, membrane covered with minute microtrichia. Anal lobe and area usually reduced, sometimes greatly so and wing appearing petiolate (Figs 57, 59, 61, 63). Posterior margin of wing sometimes with large lobe before, and excavated at, apex of M 4 (Figs 88, 89). Costa extending to M 1, with small setae, sometimes stronger basal to apex of R 1. Subcosta short, faint apically, fusing with R 1 near midpoint of R 1. R 1 short, fusing with costa in basal third of wing. R 2+3 long, ending in costa near 4/5 of wing length, nearly straight, sometimes curving slightly posteriorly near apex. R 4+5 usually weakly arched anteriorly, subparallel with M 1 apically. M 1 unbranched, nearly straight to slightly arching anteriorly beyond crossvein dm-m, with bosse alaire (slight flexion and wing indentation distal to crossvein dm-m). Membrane with weak to strong longitudinal crease running through crossvein dm-m. Crossvein dm-m placed near or just before middle of wing, half as long or less than distal section of M 4. Calypter yellow with apex narrowly brown or black (wholly yellow in C. angustipennis and C. tripilus), with fan of fine yellow setae. Halter yellow. Abdomen: Elongate cylindrical, with 6 exposed tergites, shiny dark brown usually with one or more of tergites 2–4 at least partly yellow (presence/absence and extent of yellow can vary within species), without obvious abdominal muscle plaques. Tergite 1 short, usually brown with some pruinosity, setae often black but sometimes partly white or yellow, those along posterior margin very long. Tergites 2–6 decreasing in length posteriorly, with little to no pruinosity, uniformly covered with short black setae, longer along posterior margins. Tergite 7 short (about one-third length of tergite 6), narrowly triangular in lateral view, weakly sclerotized, hidden beneath tergite 6. Sternites 1–3 often yellow with yellow setae, sternites 4–5 usually light brown to brown with black setae, sternites 3–5 with pair of slightly stronger setae near posterior margin (these setae never conspicuously thickened or truncate apically). Sternite 6 bare, membranous but sclerotized along lateral margins. Sternite 7 reduced, sclerotized, subtriangular. Sternite 8 dark brown, oval, covering hypopygial foramen and most of left side of epandrium, in air-dried specimens overlapping right side of epandrium and often infolded (this fold makes posterior tip of hypopygium appear conical or pointed), clothed with small black setae, with 2–4 stronger setae near distal tip. Abdomen containing pair of large, round, red glands (possibly testes), each positioned laterally in or near tergite 4 with posterior duct that fuse medially and run to base of hypopygium (Fig. 7); in pinned specimens, glands sometimes rupture and red substance spills into abdomen. Hypopygium (Figs 8–12): Rather small, bulbous, capping tip of but mostly external to preabdomen, not pedunculated, held oblique to long axis of abdomen in lateral view. Epandrium shiny dark brown, longer than wide, narrow in ventral view, covered with white microtrichia, denser dorsoapically (near cercus), apex tapered between surstylar lobes (usually weakly sclerotized, often paler) and partially fused with ventral lobe of surstylus, epandrial lobes absent. Hypopygial foramen left lateral, large. Surstylus shiny dark brown, with two apically appressed lobes; dorsal lobe finger-like with a few microtrichia near apex; ventral lobe spatulate, shiny dark brown with a few scattered microtrichia on ventral surface, covering apex of epandrium. Hypandrium shiny, light brown, elongate, varying from nearly triangular to ovate in ventral view, apex hood-like, pointed to bluntly flared in lateral view (apex hooked in C. furcatus), with base fused indistinguishably to epandrium; hypandrial arms fused with bacilliform sclerites, each arm medially with short apically directed sword-like lobe. Cercus short, triangular (apex rounded in C. isoaristus) with ventral margin nearly straight, yellow-brown to brown, with short yellow setae, slightly stronger near apex. Ejaculatory apodeme lever-like, articulated at base of phallus, rod-shaped with two short nearly perpendicular arms at base (forming a V-shape) that surround base of phallus. Aedeagus tubular, sclerotized, separate from (but closely associated with) broader aedeagal sheath for entire length; aedeagus with second narrow sheath, sometimes separated apically (sheath slightly shorter than aedeagus) (Fig. 11). Broader aedeagal sheath pointed or acuminate apically, sometimes minutely serrate near apex, slightly shorter than aedeagus, with apparent groove for aedeagus such that aedeagus and sheath often appear as one structure external to epandrium. Postgonites basally as pair of tubular sclerites, extending around base of phallus and arched ventrally to weakly attach to bacilliform sclerites; ventrally, from apical half of these tubular sclerites arises membranous structure that runs dorsal and parallel to aedeagus+sheath (if visible appearing whitish in pinned specimens, but almost clear and difficult to detect when macerated) narrowed and sclerotized apically with bifid apex; apex sometimes partially to wholly sclerotized and brown or with sclerotized brown rod along dorsal edge; in intact specimens apical lobes appressed side-by-side, in some macerated specimens lobes unfold (Fig. 12). Subepandrial membrane sclerotized along full-length, extending to base of cercus. Bacilliform sclerites fused medially, forming dorsoventrally oriented column with processes extended to surstyli, fused with hypandrium.
Female. Wing length 2.2–3.5 mm. Similar to male except as follows: Head: Face wider, nearly parallel-sided, grayish. Eyes with ommatidia similar in size, not noticeably enlarged near face. Antenna (Fig. 6) with scape shorter, not laterally flattened, usually as long or longer than postpedicel; postpedicel shorter, usually about as wide as long, apex rounded to subquadrate (shape of apex varies within-species, likely due to drying); arista-like stylus unmodified, sometimes tip blunted in species whose males have apical lamella. Palpus larger, triangular, usually darker. Thorax: Proepimeron with at least 1 small, white hair (bare in C. angustipennis and C. tripilus) (Fig. 6). Legs: Unmodified and without specialized setae. Mid tibia with small ventral seta near 3/4, often with 1–2 additional smaller ventral setae near 1/2 and/or near basal 1/3. Tarsomeres generally decreasing in length apically except hind tarsomere 1 shorter than tarsomere 2 (subequal in C. pennarista). Hind leg with femur, tibia and tarsus often more yellow. Wing: Broader, especially anal area, elongate oval and not obviously modified in shape. Membrane without or with weak longitudinal crease running through crossvein dm-m. Calypter with setae yellow-brown. Abdomen: Subconical, tapered posteriorly, about as long as thorax, with 5 exposed segments (i.e., narrow telescoping terminalia retractable into segment 5). Tergites usually with less yellow than male. Terminalia with segments 6 and 7 weakly sclerotized. Tergite 6 with small subapical ventral seta, with or without lateral seta. Tergite 7 with small subapical ventral seta. Tergite and sternite 8 each divided (desclerotized) medially, hemitergites dark, nearly straight, rod-shaped, loosely articulated at base. Tergite 9+10 divided, sclerotized, with 3–5 acanthophorite spines per side. Cercus short, digitiform with at least one small subapical ventral seta, sometimes with ventrobasal narrow lobe with small apical setae.
Immatures. Corpus (1988) reported rearing adults of C. sobrinus from larvae extracted from mud at seeps in Washington State, USA but these were not described.
Distribution. Species of Calyxochaetus are restricted to the New World from Alaska and Northwest Territories southeast to Nova Scotia and south to Costa Rica. The genus is most diverse in the western USA.
Remarks. The male hypopygium is quite uniform across species, with some variation in the shape of the hypandrium, rarely the cercus (e.g., C. isoaristus), and shape and color of the bifid apex of the postgonites. The placement of Calyxochaetus in the Sympycninae is supported by the tubular form of the base of the postgonites that encircle the base of the aedeagus and sheath (or phallus). This conformation of the postgonites has so far only been found in sympycnine genera including Sympycnus (Sinclair & Cumming 2006), Erebomyia Runyon & Hurley (Hurley & Runyon 2009), Telmaturgus Mik (Runyon 2012), and Syntormon Loew (Drake 2021). Males of Pseudosympycnus Robinson also have postgonites of this form (Soares & Capellari 2020), and although often placed in the Stolidosomatinae there is mounting evidence that this genus belongs in the Sympycninae (German et al. 2011; Soares & Capellari 2020). It is usually not possible to identify isolated females of Calyxochaetus to species.
The red glands in the abdomen of males (Fig. 7) could be testes. I have found similar red glands in males of other Empidoidea, e.g., in some species of Parasyntormon, Sympycnus, Pseudosympycnus Robinson, Chaetogonopteron De Meijere, Erebomyia and Rhamphomyia Meigen. The abdomen of some females has a reddish color, suggesting that males may transfer this substance (possibly spermatozoa) during copulation.
Key to Species of Calyxochaetus (males)
1 Foreleg with tarsomere 1 about 1.5X longer than tarsomere 2 (Figs 20, 22) [C. tripilus group]......................... 2
- Foreleg with tarsomere 1 less than or equal to length of tarsomere 2 (usually very short) (e.g., Figs 41, 97, 98)........... 4
2 Mid tarsus unmodified (Fig. 23); mid femur with distinct ventral setae (subequal to femur width)..... C. longitarsus sp. nov.
- Mid tarsus modified with several fine, sinuous, yellow anterior setae (Fig. 21); mid femur without distinct ventral setae.... 3
3 Face about 3 ommatidia wide at clypeus (Fig. 18); palpus white (Fig. 18); postpedicel ovate-triangular, with apex weakly pointed (Fig. 16).................................................................... C. tripilus (Van Duzee)
- Face about 1 ommatidium wide at clypeus; palpus brown; postpedicel short and broadly rounded (Fig. 15).............................................................................................. C. angustipennis (Aldrich)
4 Tarsomere 2 of mid tarsus with basal one-third to one-half slightly swollen (in dorsal and ventral views) and swollen area bearing 3–4 fine sinuous anterior setae (Figs 45, 47–49) [C. cilifemoratus group]................................... 5
- Tarsomere 2 of mid tarsus not as above................................................................... 17
5 Arista-like stylus unmodified, slender and tapering to a sharp point (Fig. 37); metepimeron wholly yellow [eastern North America].......................................................................... C. luteipes (Van Duzee)
- Arista-like stylus variously thickened, usually with apical lamella (Figs 26–36, 38); metepimeron usually partly to wholly brown [western and central North America]................................................................ 6
6 Hind femur without long ventral setae (Fig. 52); arista-like stylus with very small, nearly round apical lamella (Fig. 34); calypteral setae conspicuously long, subequal in length to fore coxa.................. C. hardyi (Harmston & Knowlton)
- Hind femur with one or more long ventral setae on distal half (e.g., Figs 50, 51, 53); arista-like stylus with larger or elongate apical lamella or evenly thickened throughout (Figs 26–33, 35, 36, 38); calypteral setae not conspicuously long.......... 7
7 Postpedicel mitten-shaped, with distinct ventral lobe (Fig. 27)............................... C. arizonicus (Harmston)
- Postpedicel more or less evenly rounded, without distinct ventral lobe........................................... 8
8 Arista-like stylus of uniform thickness throughout, without obvious lamella (Fig. 36)...................................................................................................... C. isoaristus (Harmston & Knowlton)
- Arista-like stylus with apical lamella...................................................................... 9
9 Hind femur, in dorsal view, with long, dense, erect anterior and posterior setae (Fig. 55)............................ 10
- Hind femur, in dorsal view, without long, dense, erect anterior and posterior setae (Fig. 54)......................... 11
10 Arista-like stylus with relatively narrow apical lamella (Fig. 31); fore coxa mostly yellow (in lateral view, sometimes infuscated near base); foreleg with tarsomere 3 about half length of tarsomere 4 (Fig. 41); wing with anal lobe markedly widening beyond apex of R 1 (Fig. 57)..................................................................... C. celatus sp. nov.
- Arista-like stylus with wide lamella (Fig. 29); fore coxa fuscous; foreleg with tarsomere 3 about three-quarters length of tarsomere 4 (Fig. 42); wing with anal lobe markedly widening at or before apex of R 1 (Fig. 59). C. cilifemoratus (Van Duzee)
11 Metepimeron wholly yellow (Fig. 64); arista-like stylus as in Figs 26 or 28...................................... 12
- Metepimeron partly to wholly brown (often yellow above hind coxa); arista-like stylus as in Figs 30, 32, 33, 35 or 38..... 13
12 Face about 2 ommatidia wide at clypeus; postpedicel about as long as wide; arista-like stylus with relatively large apical lamella (Fig. 26); foreleg with tarsomeres 3 and 4 subequal in length (Fig. 39) [Manitoba, Canada]......... C. anisoaristus sp. nov.
- Face less than 1 ommatidium wide at clypeus (Fig. 69, inset); postpedicel distinctly longer than wide (Fig. 28); arista-like stylus with smaller apical lamella (Fig. 28); foreleg with tarsomere 3 twice as long as tarsomere 4 (Fig. 40) [Arizona, USA]............................................................................................ C. brooksi sp. nov.
13 Hind femur with black posterior preapical seta (near midline, opposite anterior preapical seta) (Fig. 54); tarsomere 2 of foreleg without distinct anterior setae at apex; wing very narrow throughout (Figs 61, 63)................................. 14
- Hind femur without posterior preapical seta; tarsomere 2 of foreleg with 1–2 distinct anterior setae at apex (longer than width of tarsomere) (Figs 43, 44); wing not conspicuously narrow................................................... 15
14 Face narrow (2 ommatidia wide at narrowest); midleg with tarsomeres very slender, combined length of tarsomeres 2–5 distinctly longer than tarsomere 1, with tarsomere 2 almost half tarsomere 1 length (Fig. 45)....... C. distortus (Van Duzee)
- Face wide (5 ommatidia wide at narrowest) (Fig. 68, inset); midleg with tarsomeres not unusually slender, combined length of tarsomeres 2–5 less than tarsomere 1, with tarsomere 2 about one-third tarsomere 1 length (Fig. 46).... C. harmstoni sp. nov.
15 Abdomen wholly brown (Fig. 66); fore coxa and basal half of fore femur fuscous; foreleg with tarsomeres 2 and 3 subequal in length (Fig. 44); arista-like stylus with small, narrow apical lamella (Fig. 32).................... C. coloradensis sp. nov.
- Abdomen with basal tergites partly yellow (e.g., Fig. 67); fore coxa and femur yellow; foreleg with tarsomere 2 longer than tarsomere 3 (e.g., Fig. 43); arista-like stylus with larger apical lamella (Figs 30, 38)................................ 16
16 Arista-like stylus with apical lamella relatively long and narrow, usually with ventral margin slightly concave (Fig. 30); foreleg with tarsomere 3 about 1.5X longer than tarsomere 4 (Fig. 43); wing with distal section of M 4 about 4X longer than crossvein dm-m.......................................................................... C. clavicornis (Van Duzee)
- Arista-like stylus with wider apical lamella, with ventral margin nearly straight (Fig. 38); foreleg with tarsomeres 3 and 4 subequal in length; wing with distal section of M 4 about 3X longer than crossvein dm-m................. C. syilx sp. nov.
17 Fore tibia swollen (Figs 82–86); fore tarsomere 2 with slender, distally directed anterior seta near apex (Fig. 83); posterior margin of wing often with large lobe (Figs 88, 89) [C. fortunatus group]......................................... 18
- Fore tibia slender (e.g., Fig. 119); fore tarsomere 2 without distinct seta near apex; posterior margin of wing never with large lobe............................................................................................... 22
18 Wing with posterior margin excavated at apex of M 4 and with large, rounded lobe subtending excavation; distal section of M 4 nearly straight (Figs 88, 89)............................................................................ 19
- Wing with posterior margin not or weakly excavated at apex of M 4 and without large lobe; distal section of M 4 bending toward wing tip (Figs 90, 91)................................................................................. 21
19 Pleura yellow ventrally (e.g., Fig. 93) [eastern North America]................................................ 20
- Pleura wholly dark brown (Fig. 92) [western North America]................................... C. cascadia sp. nov.
20 Arista-like stylus with broad apical lamella, with most of article 2 thickened (Fig. 78); fore tibia strongly swollen (Fig. 83)................................................................................... C. fortunatus (Wheeler)
- Arista-like stylus with narrow apical lamella, with only about apical half of article 2 thickened (Fig. 81); fore tibia weakly swollen (Fig. 84).................................................................. C. leptofortunatus sp. nov.
21 Arista-like stylus with small, rounded apical lamella (Fig. 80); wing margin with very small excavation at apex of M 4 (Fig. 91); abdomen yellow laterally on tergites 2 and 3; frons glabrous, shiny.............................. C. vegetus (Wheeler)
- Arista-like stylus very slender and sharply pointed at apex, with very narrow subapical lanceolate expansion (Fig. 79); wing margin not excavated at apex of M 4 (Fig. 90); abdomen often wholly brown; frons pruinose............ C. oreas (Wheeler)
22 Foreleg with tarsomere 1 either one-half or subequal in length to tarsomere 2 (Figs 97, 98); mid tarsomere 2 not widened apically or pointed anteroapically (Figs 99–101); hind femur with long ventral setae; hind tibia without specialized ventral seta(e) near base [C. insolitus group]..................................................................... 23
- Foreleg with tarsomere 1 less than one-third tarsomere 2 length (usually very short) (e.g., Figs 116–119); mid tarsomere 2 with apex wider and pointed anteroapically (sometimes weakly so) (Figs 120–131); hind femur rarely with long ventral setae; hind tibia often with specialized ventral seta(e) near base (e.g., Figs 132–136) [C. frontalis group]........................ 24
23 Foreleg with tarsomere 1 subequal in length to tarsomere 2 (Fig. 97); hind femur with long ventral setae on distal half; arista-like stylus with apical lamella (Fig. 95)................................................. C. insolitus (Van Duzee)
- Foreleg with tarsomere 1 about half tarsomere 2 length (Fig. 98); hind femur with long ventral setae on basal half; arista-like stylus long, fuzzy, twisted and of nearly equal width throughout (Fig. 96)........... C. pennarista (Harmston & Knowlton)
24 Arista-like stylus unmodified, slender, tapering to apex (Figs 107, 112, 113)...................................... 25
- Arista-like stylus variously thickened (sometimes slightly so subapically) or with apical lamella (Figs 104–106, 108–111, 114, 115)............................................................................................... 27
25 Coxae and metepimeron mostly to wholly yellow; mid tarsomere 2 scarcely broadened apically, with inconspicuous anteroapical projection (Fig. 129); hind tibia with ventral row of small close-set setae, those near base with apex slender and bent downward (Fig. 135) [eastern North America]......................................................... C. frontalis (Loew)
- Mid and hind coxae and metepimeron infuscated; mid tarsomere 2 with small (Fig. 125) or large anteroapical projection (Fig. 130); hind tibia without specialized setae near base [western North America, Central America]....................... 26
26 Mid tarsomere 2 with short anteroapical projection, tarsomeres 3–4 nearly round and without long posterior setae (Fig. 125); wing with well-developed anal angle.......................................... C. pictipes (Harmston & Knowlton)
- Mid tarsomeres 2 and 3 with a long, thin anteroapical projection, tarsomeres 3–4 with long posterior setae (Fig. 130); wing gradually narrowed to base, without anal angle............................................ C. furcatus (Van Duzee)
27 Hind tibia with specialized ventral or posteroventral seta(e) near base (e.g., Figs 132–134, 136)...................... 28
- Hind tibia without specialized ventral or posteroventral seta(e) near base........................................ 35
28 Frons pruinose; arista-like stylus with small rather rounded lamella at apex (Figs 104, 105).......................... 29
- Frons shiny, glabrous (as in Fig. 18); arista-like stylus with elongated apical or subapical thickening (Figs 106, 108, 109, 111, 114) or with large (subequal or greater than postpedicel) lamella at apex (Figs 110, 115)............................ 31
29 Arista-like stylus with two lamellae, one near middle and another at apex (Fig. 104); hind tibia with a clump of 3–5 long ventral setae at base (Fig. 132).................................................... C. binodatus (Harmston & Knowlton)
- Arista-like stylus with one lamella at apex (as in Fig. 105); hind tibia with 1 long slender ventral seta near base (rarely with a second shorter seta) (Fig. 133).......................................................................... 30
30 Mid tarsomere 2 narrowly subtriangular with pointed anteroapical projection, tarsomeres 3–4 narrow and longer than wide (Fig. 121); hind tibia with long slender ventral seta near 1/4 (Fig. 133)................................. C. nodatus (Loew)
- Mid tarsomere 2 ovate with anteroapical projection rounded, tarsomeres 3–4 swollen and nearly round (Fig. 122); hind tibia with long slender ventral seta near 1/3................................................... C. bovanodatus sp. nov.
31 Hind femur with row of long ventral setae (Fig. 136)........................................... C. lacrima sp. nov.
- Hind femur without long ventral setae.................................................................... 32
32 Fore tarsomere 4 at least 1.5X tarsomere 3 length; mid tarsomeres 3–4 wide and flattened, distinctly wider than tarsomere 5 (Figs 126–128); arista-like stylus with apex pointed or rounded, not obliquely clipped (Figs 109–111)................. 33
- Fore tarsomere 4 subequal to tarsomere 3 length; mid tarsomeres 3–4 not distinctly widened or flattened, subequal in width to tarsomere 5; arista-like stylus with elongate narrow apical lamella that is obliquely clipped at apex (Fig. 114)............................................................................................... C. lamellicornis Parent
33 Fore tarsomere 4 broadened at base and oar-shaped, about 4X tarsomere 3 length (Fig. 118); hind tibia with 2–3 long ventral setae at base; arista-like stylus with large ovate apical lamella (Fig. 110)............................ C. remifer sp. nov.
- Fore tarsomere 4 not oar-shaped, less than 2X tarsomere 3 length; hind tibia with row of longer ventral setae on basal half (as in Fig. 134); arista-like stylus with lanceolate lamella (Figs 109, 111)........................................... 34
34 Arista-like stylus with very large lanceolate lamella (Fig. 109); scutellum with distinct blue-violet reflections................................................................................................... C. ornatus Parent
- Arista-like stylus with small lanceolate lamella (Fig. 111); scutellum without distinct blue-violet reflections (at most weak reflections)............................................................................ C. tohono sp. nov.
35 Metepimeron yellow; arista-like stylus with narrow, elongate apical lamella that is obliquely clipped at apex (Fig. 114)....................................................................................... C. lamellicornis Parent
- Metepimeron infuscated; arista-like stylus with narrowly lanceolate lamella, apex symmetrical and pointed (Figs 106, 108).. .................................................................................................. 36
36 Arista-like stylus distinctly longer than head height, distinctly enlarged and narrowly lanceolate on distal half (Fig. 106); mid tarsomere 5 about 2X as long as wide (Fig. 123); basal abdominal tergites always partly yellow (Fig. 141); desert southwest USA (Fig. 146)........................................................................ C. desertus sp. nov.
- Arista-like stylus subequal to head height, very slightly widened subapically (Fig. 108); mid tarsomere 5 about 3X as long as wide (Fig. 124); basal abdominal tergites often wholly brown; mountains near Pacific Coast and inland northwest USA (Fig. 145)............................................................................... C. sobrinus (Wheeler)
description: Published as part of Runyon, Justin B., 2024, Revision of the genus Calyxochaetus Bigot (Diptera: Dolichopodidae: Sympycninae), pp. 1-74 in Zootaxa 5539 (1) on pages 6-12, DOI: 10.11646/zootaxa.5539.1.1, http://zenodo.org/record/14240426