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

description: Calyxochaetus tripilus (Van Duzee)
(Figs 13, 14, 16, 18–21, 25)
Sympycnus tripilus Van Duzee, 1930: 52.
Calyxochaetus metatarsalis Robinson, 1966: 272 syn. nov.
Calyxochaetus tripilus: Pollet et al. (2004: 74).
Type material examined. Sympycnus tripilus: HOLOTYPE ♂, labeled: “ San Diego Co. / Desert edge / Cal. Apr. 15 ‘15/ MC Van Duzee ”; “ Sympycnus / tripilus / Holotype.VanDuzee” (CAS). PARATYPE: USA: California: Same data as holotype (1♀, USNM).
Calyxochaetus metatarsalis: HOLOTYPE ♂ collected in the state of San Luis Potosí, Mexico, labeled: “El Salto, S.L.P./ May 9, 1963 ”; “ Holotype ♂ / Calyxochaetus / metatarsalis / H. Robinson ” (USNM).
Other material examined. MEXICO: Baja California: Agua Caliente (San Carlos), 18.5 km E Maneadero, 6.vii.1973, P.H. Arnaud, Jr (1♂, CAS); Arroyo Santo Domingo, 5.7 mi E Hamilton Ranch, dam site, 23.iv.1963, H.B. Leech & P.H. Arnaud, Jr (1♂, CAS). Baja California Sur: 3.5 km WNW San Isidro, canyon/oasis, 22– 23.iv.1983, Malaise, M. Wasbauer (1♂, CSCA); Sonora: Alamos, 4.i.1971, P.H. & M. Arnaud (1♂, CAS). USA: Arizona: Mohave County: Beaver Dam Wash, Beaver Dam, 1950 ft, 13.iv.2003, JBR & RLH (2♀, MTEC); Santa Cruz County: Patagonia Lake, 3750 ft, 15.iv.2003, JBR & RLH (1♂, MTEC). California: Imperial County: Salton Beach, 12.xi.1945, ALM (1♂, USNM); Riverside County: Palm Canyon, 25.xii.1952, P.H. Arnaud (3♂, FSCA); same data except, 15.iii.1955, W.R. Richards (1♀, CNC); Whitewater Fish Hatchery, 16.i.1953, P.H. Arnaud (4♂, CAS); Thousand Palms Oasis, 25.xi.1955, W.R. Richards (2♀, CNC); same data except, 17.iii.1955 (2♀, CNC); same data except, 26.xi.1955, W.R.M. Mason (4♂, 4♀, CNC); Palm Springs, 20.xi.1943, ALM (1♂, USNM); San Diego County: Borrego Desert, Palm Canyon, 10.xi.1945, ALM (1♂, USNM). Nevada: Nye County: Ash Meadows National Wildlife Refuge, Indian Garden Springs outlet at Longstreet Road, 36°27.872′N 116°19.445′W, 30.iii.2018, JBR (2♂, MTEC); same data except, Longstreet Spring, 36°28.05′N 116°19.58′W, 23.iv.2014 (1♀, MTEC). Texas: Gillespie County: Pedernales River, 19.iii.1955, W.W. Wirth (1♂, USNM); Hale County: Plainview, 21.iv.1955, FCH (1♂, FSCA); Kimble County: Llano River, 23.v.1972, Malaise, W.W. Wirth (1♂, USNM); Maverick County: Quemado, 11.iv.1972, FCH (1♂, FSCA). Utah: Washington County: Leeds, 1.x.1939, G.F. Knowlton & FCH (1♂, CNC; 1♂, LACM); same data except, 9.vi.1940 (2♂, 1♀, CNC; 2♂, LACM); same data except, 22.v.1941 (1♂, FSCA).
Diagnosis. Males are distinguished from other known species of Calyxochaetus, except C. angustipennis and C. longitarsus sp. nov., by having a long fore tarsomere 1 (Fig. 20). Males can be distinguished from C. angustipennis and C. longitarsus sp. nov. by having a white palpus (Fig. 18) and a subtriangular postpedicel (Fig. 16). Within Calyxochaetus, a bare proepimeron in females occurs only in C. tripilus and C. angustipennis (although the female of C. longitarsus sp. nov. is unknown and could also have a bare proepimeron).
Redescription. Male. Wing length 2.2–2.5 mm. Head: Frons (Fig. 18) almost entirely glabrous, shiny dark brown with weak violet reflections, with brown pruinosity on ocellar triangle and along eye margins, and with sparse brown pruinosity below ocellar triangle. Occiput dark brown pruinose with a lateral area of silver-white pruinosity around uppermost postocular setae. Face white, narrowing to about 3 ommatidia wide at clypeus. Antenna (Fig. 16) brown; scape distinctly shorter than combined length of pedicel and postpedicel; postpedicel ovate-triangular, about 1.5X as long as wide; arista-like stylus unmodified. Palpus white, small, triangular with rounded apex. Proboscis yellow-brown. Thorax: Pleura brown with gray pruinosity, becoming yellowish ventrally in a few specimens; metepimeron yellow. Scutellum without distinct blue-violet reflections. Legs: Foreleg: Coxa, femur and tibia wholly yellow, tarsus brown from near apex of tarsomere 1. Tibia without outstanding setae. Fore tarsus (Fig. 20) unmodified with tarsomere 1 about 1.5X length of tarsomere 2. Midleg: Coxa, femur and tibia yellow, tarsus (Fig. 21) brown from apical fourth of tarsomere 1. Tarsomere 1 with fine sinuous white anterior seta at apex. Tarsomere 2 not swollen on basal half, with 2 fine sinuous white anterior setae (one placed just before and the other just beyond 1/2), with shorter, straight anteroventral seta near 2/3. Tarsomere 4 with short, fine anterior seta at apex. Tarsomere 5 with short, fine anterodorsal seta near 1/3 and similar-sized anterior seta at apex. Hindleg: Coxa yellow, femur usually light brown dorsoapically, tibia yellow becoming brown on apical half (mostly brown in a couple of specimens), tarsus brown. Femur without specialized setae, posterior preapical seta absent. Wing (Fig. 19): Narrowly oval, evenly light brown-tinged. Distal section of M 4 about 2.5X longer than crossvein dmm. Calypter wholly yellow. Abdomen: Tergite 1 brown, some specimens with small lateral yellow spot adjacent to metepimeron. Tergites 2–3 mostly yellow, sometimes brown dorsally. Tergites 4–5 yellow laterally and brown dorsally, sometimes mostly brown. Tergite 6 usually with some yellow ventrally. Sternites yellow. Hypopygium: Postgonites with apical lobes narrowly rounded, light brown.
Female. Wing length 2.4–3.1 mm. Similar to male except as follows: Head: Occiput with silver-white pruinose band. Face wider, only slightly narrowed near middle, silver-gray. Antenna (Fig. 14) shorter; postpedicel short, rounded. Palpus larger, triangular, yellowish white becoming brown basally. Thorax: Proepimeron bare. Propleuron, notopleuron and adjacent areas of scutum with gray pruinosity. Legs: Unmodified, without specialized setae. Hindleg with femur, tibia and basal half of tarsomere 1 yellow. Wing: Broader, usually with slightly darker brown tinge. Abdomen: Tergites 2–5 generally brown dorsally and yellowish ventrally, tergite 5 sometimes wholly brown.
Distribution and seasonal occurrence. Known from the southwestern USA and northern Mexico (Fig. 25). Adults appear to be active year-round but have been most commonly collected in the fall and spring. Robinson (1966) found adults in San Luis Potosí, Mexico, hovering over wet limestone by a small, shaded pool. I have collected adults at Ash Meadows National Wildlife Refuge, Nevada, USA, by sweeping rocks in the shade of a culvert and rocks shaded by cattails at the edge of a large spring.
Remarks. The arrangement of setae on the mid tarsus of males of C. angustipennis and C. tripilus suggests a relationship with the C. cilifemoratus species group.
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 16-17, DOI: 10.11646/zootaxa.5539.1.1, http://zenodo.org/record/14240426