Calyxochaetus celatus sp. nov. (Figs 31, 41, 49, 55, 57, 65, 73) Type material. HOLOTYPE ♂, labeled: “ MONTANA: Beaverhead / Co., Big Sheep Creek / 9 mi SW Dell 6570ꞌ/ N44°36.22′; W112°48.25′ / 04JUL2010; J.B. Runyon ”; “HOLOTYPE/ Calyxochaetus / celatus / J.B. Runyon [red label]” (USNM) (Fig. 65). PARATYPES: USA: Montana: Same data as holotype (1♂, 1♀, USNM; 1♂, MTEC). Other material examined. CANADA: Alberta: 11 mi W of Banff, Banff National Park, 4500 ft, 11.vii.1955, G.E. Shewell (1♀, CNC); 13 mi N of Banff, Banff-Jasper Highway, 4500 ft, 26.vii.1955, R. Coyles (1♂, 1♀, CNC); same data except, 13 mi from Banff, vii.1955 (2♂, 2♀, CNC). British Columbia: Oliver, 13.vii.1965 (1♂, CNC); Hush Lake, 16 mi N of Quesnel, Route 97, 7.vi. 1983, R.S. & V.L. Zack (3♂, 2♀, WSU); 10 mi E Vanderhoof, Route 16, sedge pond, 6.vi.1983, R.S. & V.L. Zack (2♂, 1♀, WSU); Salmon Arm, 8.vi.1988, A. Borkent (3♂, CNC). USA: Alaska: Hoonah-Angoon Census Area: Sebree Island, 22.vii.1965, D.M. DeLong (2♂, USNM). California: Alpine County: Indian Creek Lake, 15.vi.1979, G.E. Bohart (2♂, LACM); Lassen County: Bogard Ranger Station, 3.vii.1955 (1♂, FSCA); Nevada County: near Hobart Mills, 10.x.1952, E.I. Schlinger (1♂, FSCA); Sagehen Creek. near Hobart Mills, 15.vii.1964, R.M. Bohart (1♂, UCD). Colorado: Eagle County: Tennessee Pass, 21.vii.1966, FCH (1♂, FSCA); Gunnison County: Crested Butte, 8.viii.1968, FCH (1♂, FSCA); Summit County: Vail Pass, 21.vii.1966, FCH (3♂, FSCA). Idaho: Adams County: Route 55, 6 mi S of New Meadows, 26.vi.1980, R.S. Zack (1♂, WSU); Kootenai County: Bayview, vii.1973, FCH (9♂, FSCA). Montana: Deer Lodge County: Georgetown Lake, 31.vii.1923, ALM (1♂, USNM); Gallatin County: Hyalite Dam, 20 mi S of Bozeman, 12.vii.2000, RLH & JBR (1♂, MTEC); Moose Creek, 25 mi SE of Bozeman, 6300 ft, 4.vii.2002, JBR (2♂, 1♀, MTEC); Gallatin River, 17 mi S of Big Sky, 6725 ft, 13.viii.2005, JBR & RLH (1♂, 1♀, MTEC); Meadow Creek, 45.06987 –111.26913, 4.viii.2019, JBR (1♂, MTEC); Glacier County: Babb, 24.vii.1970, FCH (4♂, 1♀, CAS; 5♂, FSCA); Jefferson County: Milligan Creek at Milligan Canyon, 6 mi W of Three Forks, 4370 ft, 6.vii.2002, RLH & JBR (1♂, MTEC); Madison County: Cliff Lake, inlet near island, 44°46.016’N 111°33.000’W, 1.viii.2015, JBR (2♂, 1♀, MTEC); 5.4 mi E of Alder, 5400 ft, 17.viii.1993, RLH (1♂, MTEC); Meagher County: Holmstrom Ditch, 5650 ft, 46°43.87’N 110°50.99’W, 12.ix.2009, JBR (1♂, MTEC); Missoula County: Gold Creek, 1220 m, 46°59.059′N 113°40.683′W, 27.vi.2017, B.J. Sinclair (1♂, CNC); Phillips County: Malta, 23.vii.1970, FCH (2♂, FSCA); Toole County: Shelby, 24.vii.1970, FCH (5♂, FSCA). Oregon: Baker County: Baker [City], 25.vii.1965, FCH (3♂, FSCA); Clackamas County: Devils Falls, 30.vii.1965, FCH (1♂, FSCA); Union County: La Grande, 12.vi.1977, FCH (17♂, FSCA); Wasco County: The Dalles, 27.vii.1965, FCH (2♂, FSCA). Utah: Duchesne County: Duchesne, 24.vi.1951, FCH (1♂, FSCA). Washington: Asotin County: Fields’ Spring State Park, 4 mi S of Anatone, 3600 ft, small pond, Puffer Butte, W. Turner (4♂, WSU). Wyoming: Park County: Yellowstone National Park, Glen Creek, 7300 ft, 44°55.94′N 110°43.67′W, 28.viii.2009, JBR (1♂, MTEC); same data except, Joffee Lake, 6550 ft, 44°56.86′N 110°42.02′W (1♂, MTEC). Diagnosis. This species is very similar to C. cilifemoratus (Van Duzee), with males of both species distinguished by having long setae on anteroventral to posteroventral surface of hind femur (Fig. 55). Males of C. celatus sp. nov. differ in having a longer arista-like stylus with narrower apical lamella, fore coxa usually mostly to wholly yellow (distinctly fuscous in C. cilifemoratus), foreleg with tarsomere 3 about half the length of tarsomere 4 (tarsomere 3 three-quarters length of tarsomere 4 in C. cilifemoratus; cf. Figs 41 and 42), wing with the anal lobe markedly widening beyond apex of R 1 (markedly widening at or before apex of R 1 in C. cilifemoratus) and with distal section of M 4 about 4X longer than crossvein dm-m (3X longer in C. cilifemoratus) (cf. Figs 57 and 59). Description. Male. Wing length 2.7–3.0 mm. Similar to C. cilifemoratus except as noted: Head: Arista-like stylus (Fig. 31) slightly longer than head height, with narrower apical lamella nearly spatulate but slightly asymmetrical. Legs: Foreleg: Coxa wholly yellow or darkened near base (in lateral view, often appearing brownish in anterior view), femur usually wholly yellow but slightly infuscated on basal half in a few specimens. Tarsomere 3 (Fig. 41) about half as long as tarsomere 4, or slightly longer. Hindleg: Coxa yellow, usually infuscated near base, femur (Fig. 55) mostly yellow, brownish on apical third or less (often only brown dorsoapically). Wing (Fig. 57): Anal lobe markedly widening beyond apex of R 1. Distal section of M 4 about 4X longer than crossvein dm-m. Abdomen: Tergite 2 almost always partly to mostly yellow laterally. Tergite 3 usually brown, rarely with small yellow lateral spot. Female. Wing length 2.5–2.9 mm. Similar to C. cilifemoratus except as noted: Legs: Fore coxa wholly yellow or darkened with gray pruinosity at base. Wing: Distal section of M 4 about 3X longer than crossvein dm-m. Abdomen: Tergite 2 usually with small yellow lateral spot at base (wholly brown in one specimen), remaining tergites brown. Distribution and seasonal occurrence. This species is known from southern Alaska south to Colorado and Utah, and northern California (Fig. 73). Adults have been collected from June to early October. Etymology. The specific epithet is Latin, “concealed”, due to the species not previously being recognized as distinct from C. cilifemoratus. Remarks. Adults were collected at the type locality by sweeping through tall, dense grasses and rushes of an open marshy area adjacent to Big Sheep Creek in southwest Montana (Fig. 4). Specimens from Alaska and California generally have a wider lamella on the arista-like stylus, but otherwise match C. celatus sp. nov. In such cases, the non-antennal characters provided in the key will separate C. celatus sp. nov. from C. cilifemoratus.

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 21-22, DOI: 10.11646/zootaxa.5539.1.1, http://zenodo.org/record/14240426