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

description: Calyxochaetus isoaristus (Harmston & Knowlton)
(Figs 36, 48, 60, 75)
Sympycnus isoaristus Harmston & Knowlton, 1940: 402.
Calyxochaetus isoaristus: Pollet et al. (2004: 74).
Type material examined. HOLOTYPE ♂, labeled: “ G.F. Knowlton / F.C. Harmston / Collectors”; “ Cedar Breaks / Utah / Aug 3, 1938 ”; “Type No/ 54295/ USNM”; “HOLOTYPE/ Sympycnus / isoaristus / n. sp. F.C.H. - G.F.K”; “ Sympycnus / isoaristus H. & K./ Det. 1940 F.C. Harmston ” (USNM).
Other material examined. USA: Arizona: Apache County:White Mountains,Colter Ranch, 9200 ft, 28.vi.1947, J.L. Sperry (1♂, USNM); Alpine, 26.vi.1968, FCH (1♂, FSCA); Graham County: Pinaleno Mountains, Hospital Flat, 8950 ft, 2.viii.1965, H.B. Leech (3♂, CAS). Colorado: Eagle County: Tennessee Pass, 21.vii.1966, FCH (1♂, FSCA); Larimer County: Parvin Lake, 25.v.1974, FCH (1♂, FSCA); Mesa County: Glade Park, 8.vii.1953, Gurney (1♂, USNM); San Miguel County: Ophir, 13.vi.1961, FCH (1♂, FSCA). Idaho: Fremont County: Warm River, 5300 ft, N44°07.18’ W111°18.86’, 30.vii.2014, JBR (1♂, 5♀, MTEC); Teton County: Little Pine Creek, 6600 ft, N43°34.39’ W111°12.34’, 4.viii.2014, JBR (2♂, 1♀, MTEC). Montana: Beaverhead County: Pioneer Mountains, Canyon Creek Road, hillside spring, 1884 m, N45.6571° W112.7933°, 8.viii.2020, JBR (1♂, MTEC); Carbon County: Pryor Mountains, Sage Creek, 5500 ft, 21.vi.2003, JBR (1♂, 2♀, MTEC); Cascade County: Neihart, 5600 ft, 27.vi.2003, JBR (1♂, 4♀, MTEC); Gallatin County: Gallatin River, Central Park, 29.vi.2000, RLH & JBR (1♂, MTEC); Bridger Mountains, Corbley Gulch, 15.vii.2000, JBR (1♂, 1♀, MTEC); Bridger Mountains, Truman Gulch, 5400 ft, 21.vii.2000, JBR (1♂, MTEC); Leverich Canyon, 6 mi S Bozeman, 5600 ft, 12.vii.2001, JBR (2♂, 3♀, MTEC); Moose Creek, 25 mi SE Bozeman, 6300 ft, 4.vii.2002, JBR (8♂, 5♀, MTEC); Cherry River fishing access, 1 mi. N Bozeman, 7.vii.2002, JBR (1♂, MTEC); Blackmore Creek at Hyalite Reservoir, 20 mi. S Bozeman, 6700 ft, 6.vii.2002, JBR (2♂, 3♀, MTEC); same data except, 18.vii.2002, RLH & JBR (2♂, MTEC); Olsen Creek Road, 2.4 mi E Bridger Creek Road, seep, 6450 ft, 5.viii.2002, JBR (1♂, 1♀, MTEC); Bozeman Creek, 6 mi. S Bozeman, 5300 ft, N45°35.08’ W111°01.42’, 26.vii.2008, JBR (3♂, 1♀, MTEC); Lick Creek, 2 mi N Hyalite Reservoir, 6700 ft, N45°30.51′ W110°58.80′, 3.viii.2009, JBR (1♂, MTEC); Gallatin River, Cameron Bridge, 2 mi. SW Belgrade, 18.vii.2010, JBR (2♂, MTEC); Meadow Creek, 45.06987° -111.26913°, 4.viii.2019, JBR (2♂, MTEC); Madison River, Greycliff, N45.7205° W111.5179°, 8.viii.2021, JBR (2♂, 1♀, MTEC); Jefferson County: Milligan Canyon, Milligan Creek, 6 mi. W Three Forks, N45°53.26′ W111°40.72′, 6.vii.2002, RLH & JBR (5♂, 1♀, MTEC); same data except, 21.vii.2001 (1♂, MTEC); same data except, 16.vii.2011, JBR (5♂, MTEC); same data except, 1.vii.2018 (1♂, MTEC); Hartman Creek, 5450 ft, N45°56.96′ W112°17.49′, 29.vii.2013, JBR (1♂, 1♀, MTEC); Lewis and Clark County: Little Prickly Pear Creek, 8 mi. S Wolf Creek, 3825 ft, 29.vi.2003, JBR (1♂, 5♀, MTEC); South Fork Little Prickly Pear Creek, 18 mi. NW Helena, 5100 ft, 17.vii.2003, JBR & D. Weaver (1♂, MTEC); Liberty County: Sweet Grass Hills, East Butte, Iron Creek, 4950 ft, 48°50.96′N 111°05.89′W, 28.vi.2003, JBR (2♂, MTEC); Madison County: Mill Creek, 7370 ft, N45.4872° W112.0142°, 16.vii.2012, JBR (1♂, MTEC); Cliff Lake, inlet near island, 44°46.016′N 111°33.000′W, 1.viii.2015, JBR (4♂, 2♀, MTEC); South Boulder River, N45.6475° W112.0259°, 11.vii.2021, JBR (1♂, MTEC); Park County: Pine Creek Campground, 15 mi. S Livingston, 5600 ft, 21.vii.2002, JBR (2♂, MTEC); Phillips County: Little Rocky Mountains, Montana Gulch Campground, Landusky, 4000 ft, 14.vii.2001, JBR (1♂, 1♀, MTEC); Ravalli County: Dam Creek, 2 mi. NW Skalkaho Pass, 7255 ft, 18.viii.2002, RLH & JBR (1♂, MTEC); valley peatland, 3990 ft, N46.0753° W114.2108°, 10.vii.2020, JBR (4♂, 2♀, MTEC); Stillwater County: Woodbine Falls, 8 mi. SW Nye, 5500 ft, 7.vii.2001, JBR (1♂, MTEC); Silver Bow County: Jon Gulch, 1785 m, N45.8954° W112.4724°, 28.vii.2021, JBR (2♂, MTEC); Sweet Grass County: road near Hells Canyon campground, 45°21.76′N 110°13.08′W, 26.vii.2016, JBR (3♂, MTEC). New Mexico: Catron County: Luna, 25.vi.1968, FCH (3♂, FSCA); Taos County: Tres Ritos, 8350 ft, 16.vii.1993, RLH (4♂, 11♀, MTEC). Oregon: Baker County: Baker City, 25.vii.1965, FCH (3♂, FSCA). Texas: Uvalde County: Speir Ranch, 3 mi. NW Uvalde, at light, 5.v.1977, T. Eichlin & M. Wasbauer (1♂, CSCA). Utah: Cache County: Tony Grove Creek, 1–6.viii.1990, W.J. Hanson (1♂, LACM); Uintah County: White Rocks Canyon, 26.vi.1940, G.F. Knowlton & FCH (4♂, LACM); Wasatch County: Little Hobble Creek, 4.5 mi. SE Wallsburg, 6200 ft, 26.vi.2001, RLH (8♂, 17♀, MTEC). Washington: Lewis County: Toledo, 23.vii.1960 (1♂, FSCA). Wyoming: Lincoln County: Salt Creek, 10 mi NE Geneva, 6650 ft, 12.viii.2005, JBR & RLH (1♂, 2♀, MTEC); Little Greys River, 6900 ft, 43°04.90′N 110°42.03′W, 7.viii.2014, JBR (1♂, 1♀, MTEC); Park County: Yellowstone National Park, Glen Creek, 7300 ft, 44°55.94′N 110°43.67′W, 28.viii.2009, JBR (8♂, 1♀, MTEC); Yellowstone National Park, Joffee Lake, 6550 ft, 44°56.86′N 110°42.02′W, 28.viii.2009, JBR (2♂, 3♀, MTEC); Teton County: Yellowstone National Park, Imperial Geyser, 2.viii.1934, ALM (1♂, USNM).
Diagnosis. Males are distinguished from other species of Calyxochaetus by having the arista-like stylus slightly thickened and of uniform thickness throughout, without an obvious lamella, not elongate and twisted (Fig. 36).
Redescription. Male. Wing length 1.9–2.2 mm. Head: Frons brown pruinose, not glabrous. Face silver-white, narrowing to about 2 ommatidia wide at clypeus. Antenna (Fig. 36) brown; scape laterally flattened, slightly shorter than length of postpedicel; postpedicel elongate oval with somewhat pointed apex, about 1.5X as long as wide; arista-like stylus slightly and uniformly thickened throughout with blunted apex, in some specimens apex indistinctly broadened. Palpus small, oval, brown with pale apex. Thorax: Pleura brown with gray pruinosity, usually with bluish hue; metepimeron concolorous with pleura, becoming yellow above hind coxa. Legs: Foreleg: Yellow, except tarsus brown from near middle of tarsomere 3. Tibia slender, sometimes with very small posterodorsal seta near 2/5. Tarsomere 1 very short, about as long as wide. Tarsomere 2 half tibia length, with 2 fine yellowish anterior setae at apex. Tarsomere 3 slightly shorter than tarsomere 2. Tarsomeres 4 and 5 subequal in length. Midleg: Yellow, except coxa infuscated with yellow ground color visible, tibia yellow-brown, tarsus brown from near middle of tarsomere 1. Tarsomere 1 subequal to combined length of tarsomeres 2–5, with 2 fine sinuous yellow anterior setae at apex. Tarsomere 2 (Fig. 48) with basal half slightly swollen, bearing 3 fine sinuous yellow anterior setae. Tarsomere 4 with fine sinuous yellow anterior seta at apex. Tarsomere 5 with 1–2 shorter, fine anterior setae. Hindleg: Yellow, except coxa sometimes faintly infuscated near base, femur light brown dorsoapically, tibia light brown, tarsus brown. Femur with anteroventral row of slender yellow setae, increasing in length distally, only distal-most seta distinctly longer that femur width; posterior preapical seta absent. Tibia with row of finer, denser ventral setae (subequal to tibia width) on basal half. Wing (Fig. 60): Tinged with brown on anterior half. Anal lobe evenly expanding to opposite apex of R 1 then flattened with weak projection before apex of M 4. Posterior margin slightly indented at apex of M 4. Distal section of M 4 about 5X longer than crossvein dm-m. Abdomen: Tergite 2 broadly yellow laterally. Tergite 3 usually broadly yellow laterally, rarely mostly brown. Tergite 4 yellow-brown to brown. Hypopygium: Cercus short and broad with rounded apex. Postgonites with apical lobes rather pointed, whitish and translucent.
Female. Wing length 2.2–2.5 mm. Similar to male except as follows: Head: Face wide, nearly parallel-sided, gray. Clypeus light gray. Antenna with postpedicel short, wider than long, subrectangular, with flat apex; arista-like stylus unmodified but usually with apex blunted. Palpus much larger, triangular, rounded apically, brown with slight gray pruinosity, yellow setulae and 1–2 brown setae. Thorax: Proepimeron with 1–3 small white hairs. Legs: Unmodified, without specialized setae. Hind tibia yellow, becoming light brown at apex. Hind tarsomere 1 yellow-brown on basal half. Wing: Elongate oval with posterior margin evenly rounded at base, rather flattened before apex of M 4. Distal section of M 4 about 3.5X longer than crossvein dm-m. Abdomen: Mostly dark brown, tergite 2 with yellow ventrolateral spot.
Distribution and seasonal occurrence. Broadly distributed in the Rocky Mountains of the USA and higher elevations in southwestern Utah and eastern Arizona, with disjunct records from western Washington, eastern Oregon, and Texas (Fig. 75). Adults have been collected May through August.
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 32-34, DOI: 10.11646/zootaxa.5539.1.1, http://zenodo.org/record/14240426