Acanthocnema albibarba ( Loew, 1869 )

Sinclair, Bradley J., 2025, Revision of the Nearctic species of Acanthocnema Becker, 1894 (Diptera: Scathophagidae), European Journal of Taxonomy 1026, pp. 304-337 : 307-311

Acanthocnema albibarba ( Loew, 1869)

Figs 4–12, 63

Cordilura albibarba Loew, 1869: 183 . Type locality: New Hampshire, USA.

Acanthocnema albibarba – Curran 1929: 133 (new combination). — Vockeroth 1965: 835 (catalogue); 1987: 1091, fig. 103.33 (fore leg).

Diagnosis

This species is distinguished by the yellowish to yellowish-brown body and legs, base of postpedicel yellow, proepimeral seta present, wing crossveins cloudy, and posthumeral (presutural intra-alar) seta present.

Type material

Holotype (based on online images: https://mczbase.mcz.harvard.edu/guid/ MCZ:Ent:13156)

USA – New Hampshire • ♂; “N.H.; albibarba / m. // Loew / Coll. // Type / 13156 [red label] // albibarba / Loew // MCZ-ENT / 00013156 / data matrix code”; MCZ .

Other material examined

CANADA – Newfoundland and Labrador • 1 ♀; St. John’s, Agric. Exp. Stn. ; [ 47.514° N, 52.784° W]; 20 Jul. 1967; J.F. McAlpine leg.; CNC . – Nova Scotia • 1 ♀; Cape Breton Highlands NP, Lone Shieling ; [ 46.810° N, 60.733° W]; 11 Jul. 1983; J.R. Vockeroth leg.; swept along fast rocky stream; CNC . – Ontario • 1 ♀; Dunrobin ; [ 45.42° N, 76.02° W]; 28 May 1967; H.J. Teskey leg.; CNC • 1 ♀, 1 puparium;

Fergus; [ 43.691° N, 80.386° W]; 18 Apr. 1993; S.A. Marshall leg.; puparium in watercress; DEBU. – Quebec • 1 ♀; Abbotsford; [ 45.443° N, 72.863° W]; 29 May 1968; G.E. Shewell leg.; CNC .

USA – Maine • 1 ♂, 1 ♀; Mt Katahdin, Hunt Trail ; [ 45°53′44″ N, 68°58′53″ W]; 1600–2400 ft a.s.l.; 1–6 Jul. 1968; D.M. Wood leg.; CNC • 1 ♂; same data as for preceding; KUMF • 1 ♀; same data as for preceding; [ 45°53′53″ N, 68°57′14″ W]; 3800 ft a.s.l.; 29 Jun. 1968; CNC • 1 ♀; Pittston ; [ 44°13′18″ N, 69°45′20″ W]; 3 Aug. 1930; A.L. Melander leg.; USNM . – New Hampshire • 1 ♂; Lost River ; [ 44.020° N, 71.742° W]; 7 Jul. 1931; A.L. Melander leg.; USNM • 1 ♀; White Mtns, The Flume ; [ 44°06′ N, 71°14′W]; 7 Jul.1938; A.L. Melander leg.; USNM • 1 ♀; White Mtns , Morrison; USNM . – New York • 1 ♀; Adirondacks, Avalanche Trail ; [ 44.182° N, 73.963° W]; 30 Jul. 1929; A.L. Melander leg.; CNC • 1 ♂; Whiteface Mt ; [ 44°22′43″ N, 73°53′06″ W]; 4000 ft a.s.l.; 19 Jul. 1962; J.R. Vockeroth leg.; CNC . – Vermont • 1 ♀; Peru; [ 43.233° N, 72.893° W]; 15 Jul. 1931; A.L. Melander leg.; USNM .

Description

Body yellowish to yellowish brown, with dense white pruinescence. Body length: 4.2–5 mm; wing length: 4.3–5.0 mm.

Male

HEAD ( Fig. 4). Frontal vitta yellow to yellowish brown anteriorly, matt; fronto-orbital plate brown, with numerous dark setulae. Chaetotaxy: anterior orbital seta proclinate, posterior 2 orbital setae lateroclinate; 3 inclinate frontals; 1 ocellar, 1 inner vertical, 1 outer vertical; postocellar setae weak, divergent; row of dark postocular setae; 1 vibrissa, 1 strong subvibrissa. Gena silvery pruinescent, depth one-quarter eye height; postgenal setae white, soft, 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 scattered white setae, longer than width of prementum. Antenna brown, postpedicel yellow at base of arista insertion; postpedicel rounded apically, 2 × as long as broad. Arista pubescent on basal third and bare apically.

THORAX ( Figs 5–6). Dark brown, paler laterally; whitish vitta along acrostichal series anteriorly. Acrostichals biserial, short, slender; 2+3 dorsocentrals; 1+2 intra-alars; 1+1 supra-alars; 1–2 postpronotals; 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 present. 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. 5). Yellow, slightly darker apically or posterior face of femora and tibia brown. Fore femur with 3 posteroventral setae extending beyond dense setulae; 5–6 evenly spaced 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 spinules ventrally. Fore tarsomere 1 with dense mat of anterior setulae. Mid femur with 2 long anteroventral setae on basal half; row of 5–6 anterior setae; 1 preapical anterior and 2 posterior preapical setae. Mid tibia with 1 anterodorsal seta beyond mid-length and 1 preapical dorsal seta; 1 anteroventral seta and 1 posteroventral apical seta. Hind femur with row of 4–6 anterodorsal setae; several widely spaced anteroventral and posteroventral setae. Hind tibia usually with 2 anterodorsal setae on either side of mid-length; 1 posterodorsal seta near mid-length; 1 dorsal preapical seta; 1 anteroventral apical seta.

WING ( Fig. 7). Infuscate, with clouding about apex of R 1 and r-m and dm-m crossveins and R 2+3 distal to cell dm; veins black; crossvein dm-m nearly at right angles, not aligned with M 4; M 4 beyond cell dm weakened to wing margin, one-half length of crossvein dm-m; CuA+CuP weakened beyond basal third, not reaching wing margin. Calypteres and halter yellow.

ABDOMEN. Similar to thorax, brownish dorsally, with greyish pruinescence; with long setae. Sternite 4 slightly wider than long ( Fig. 8). Sternite 5 broad, with pair of cylindrical lobes; long setae on basal half of lobes, apex slightly boot-shaped ( Fig. 8). Terminalia ( Figs 9–10): Epandrium rounded, narrow with long setae, especially ventrolateral setae long and wavy, nearly as long as height of epandrium. Cercus short, apical margin rounded in lateral view; cerci closely approximated medially, with setae longer than cercus. Surstylus digitiform, somewhat flattened; apex rounded, with medial marginal tip; long wavy setae on apical half, longer than length of surstylus (projecting free in dry, undissected specimens). Phallapodeme elongate, rod-shaped. Pregonite strongly recurved with several long setae at mid-length; apex flattened with single short subapical seta. Postgonite gently arched with rounded apex. Ejaculatory apodeme C-shaped with expanded ejaculatory duct. Distiphallus sickle-shaped with jagged inner margin.

Female

Similar to male except, palpus yellowish brown; without long pale setae on occiput and proboscis; abdomen dark, subshiny; terminalia not dissected.

Distribution

This species is known from northeastern North America, recorded from Newfoundland to central southern Ontario ( Fig. 63).

Remarks

A female specimen was reared from a puparium ( Figs 11–12) collected in watercress. The fore leg of this species was illustrated in Vockeroth (1987: fig. 33).