Acanthocnema ruficauda Curran, 1929

Sinclair, Bradley J., 2025, Revision of the Nearctic species of Acanthocnema Becker, 1894 (Diptera: Scathophagidae), European Journal of Taxonomy 1026, pp. 304-337 : 323-327

Acanthocnema ruficauda Curran, 1929

Figs 41–48, 62

Acanthocnema ruficauda Curran, 1929: 133 . Type locality: Tennessee Pass, Colorado, USA.

Diagnosis

This species is distinguished by the brownish body and yellowish legs, male postpedicel yellow, anterior orbital seta proclinate, proepimeral seta absent, wing infuscate, and male postgena, prementum and fore coxae with long silky white setae.

Type material

Holotype

USA – Colorado • ♂; “ Tennessee Pass [ 39°21′45″ N, 106°18′40″ W] / 10240ft Colo // JM Aldrich / VII-[2?]7 coll // Type No. / 41178 / U.S. N.M. [red label] // Acanthocnema / TYPE / ruficauda / Curran [red label] // Acanthocnema / ruficauda / Curran / det. / C.H. Curran // USNMENT / 01234705 [data matrix]”; USNM.

Other material examined

USA – Colorado • 1 ♀; Mt Evans, Doolittle Ranch ; [ 39°40′34″ N, 105°36′08″ W]; 9800 ft a.s.l.; 25 Jul. 1961; W.R.M. Mason leg.; CNC • 1 ♂; San Juan Co., Pasture Ck ; 37°38′48″ N, 107°50′55″ W; 10154 ft a.s.l.; 18 Jun. 2017; J.M. Cumming leg.; CNC. – New Mexico • 1 ♂; Otero Co., Sacramento Mtns, Bluff Springs , ca 16 mi. of W Mayhill; [ 32.831° N, 105.738°W]; 8000 ft a.s.l.; 15 Aug. 1993; J.E. O’Hara leg.; CNC, CNC828172 .

Description

Body brownish ( Fig. 41), with dense white pruinescence. Body length: 5.5–6 mm; wing length: 5.8– 5.9 mm.

Male

HEAD ( Figs 41–43). Frontal vitta yellow to orange anteriorly, matt; fronto-orbital plate brown, with numerous dark setulae. Chaetotaxy: anterior orbital seta proclinate, posterior 2 orbital setae lateroclinate; 3–4 inclinate frontals; 1 ocellar, 1 inner vertical, 1 outer vertical; postocellar setae weak, divergent; row of dark postocular setae; 1 vibrissa, 1–2 strong subvibrissae. Gena yellow with silvery-white pruinescence, depth one-third eye height; postgenal setae white, soft, silky and wavy, longer than width of postgena. Face, parafacial and occiput silvery pruinescent. Palpus yellowish white with long white setae. Proboscis with broad, shiny prementum, with long silky, wavy setae, similar to postgenal setae. Antenna with scape and pedicel yellow to brownish, postpedicel yellow; postpedicel rounded apically, 2 × as long as broad. Arista pubescent on basal third and bare apically.

THORAX ( Fig. 41). Brown, darker beneath dorsocentral row. Acrostichals biserial, short, slender; 2+3 dorsocentrals; 0+2 intra-alars; 1–2+1 supra-alars; 1 postpronotal; 2 notopleurals, 2 postalars; scutellum with pair of strong apical setae and pair of strong basal setae; scutellar disc with a few scattered setulae. Proepisternal seta present. Proepimeral seta absent ( Fig. 42). Anepisternum with dark setulae on posterior half and 1 long seta and several long thinner setae near posterior margin. Katepisternum with 1 strong, long seta in posterodorsal corner and numerous yellow setulae.

LEGS ( Fig. 41). Yellowish brown. Fore femur with row of 5–6 widely spaced, pale posteroventral setae extending beyond long, dense setulae; 5–6 evenly spaced dark dorsal setae, shorter than width of femur. Fore tibia with ventral apical spur, 1 anterodorsal slightly beyond mid-length, 1 preapical dorsal seta and 1 posteroventral seta proximal to spur; biserial row of short anteroventral spinules; long posteroventral setae near mid-length, longer than width of tibia. Fore tarsomere 1 with dense mat of anterior setulae. Mid femur with row of 5–6 widely spaced, extending beyond long, dense setulae; row of 5–6 anterior setae; 1 preapical anterior seta and 1 posterior preapical seta. Mid tibia with 1 posterodorsal seta at mid-length, 1 anterodorsal seta beyond mid-length and 1 preapical dorsal seta; apex of circlet of 4–5 strong setae. Hind femur with row of 4–6 anterodorsal setae and several widely spaced anteroventral and posteroventral setae. Hind tibia usually with 2 anterodorsal on either side of mid-length; 1 posterodorsal seta beyond mid-length; 1 dorsal preapical seta; 1 anteroventral apical seta.

WING ( Fig. 41). Infuscate, with faint clouding about r-m and dm-m crossveins; veins dark; crossvein dm-m nearly at right angles, not aligned with M 4; M 4 beyond cell dm weakened to wing margin, one-quarter length of crossvein dm-m; CuA+CuP weakened beyond basal third, reaching wing margin. Calypteres and halter yellow to orange.

ABDOMEN. Similar to thorax, brownish dorsally, with greyish pruinescence; with short dark setae, tergite 2 with longer setae. Sternite 4 rectangular with strong black lateral setae, nearly as long as sternite ( Fig. 44). Sternite 5 broad, with pair of cylindrical lobes, curved medially; long setae on basal half of lobes ( Fig. 45). Terminalia ( Figs 45–46) (undissected): Epandrium rounded, narrow with long setae. Cercus long, narrow, apical margin rounded in lateral view; cerci closely approximated medially, with apical setae. Surstylus elongate with round apex; long wavy setae on apical half, longer than length of surstylus.

Female

Similar to male except, pedicel brown; without long pale setae on occiput, proboscis and fore coxa; tergite 7 subtriangular, fused anterolaterally with sternite 7, dorsally tapered and medially divided ( Fig. 47); sternite 7 subtriangular, fused anterodorsally with tergite 7; tergite 8 U-shaped, enclosing proctiger, narrowly divided medially, obliquely angled; sternite 8 divided into pair of rounded digitiform lobes, directed dorsally and slender in dorsal view; epiproct and hypoproct small, triangular; cercus oval, thinly sclerotized ( Fig. 47). Three spermathecae spherical, narrow and tapered posteriorly into duct ( Figs 47–48).

Distribution

This species is recorded from Colorado and New Mexico ( Fig. 62) and Utah ( Vockeroth 1965), but specimens from the latter state were not located during this study.