Acanthocnema capillata ( Loew, 1872 )

Sinclair, Bradley J., 2025, Revision of the Nearctic species of Acanthocnema Becker, 1894 (Diptera: Scathophagidae), European Journal of Taxonomy 1026, pp. 304-337 : 311-314

Acanthocnema capillata ( Loew, 1872)

Figs 13–20, 61

Cordilura capillata Loew, 1872: 98 . Type locality: New Hampshire, USA.

Acanthocnema capillata – Curran 1929: 133 (new combination). — Vockeroth 1965: 835 (catalogue).

Diagnosis

This species is distinguished by the blackish ground colour, male palpus yellow, orbital setae lateroclinate, fore tibia with row of short, strong, black anteroventral setae proximal to ventral preapical spur and male sternite 5 with paired apical lobes.

Type material

Holotype (based on online images: https://mczbase.mcz.harvard.edu/guid/ MCZ:Ent:13158)

USA – New Hampshire • ♀; “N.H. // capillata / m. // Loew / Col l. // Type / 13158 [red label] // MCZ-ENT / 00013158 / data matrix code”; MCZ .

Other material examined

CANADA – Quebec • 1 ♂; Forillon NP, Gaspésie, La Chute Trail ; 48°50′ N, 64°16′ W; 24 Aug. 2016; B.J. Sinclair leg.; waterfall spray zone; CNC • 2 ♂; Mt Orford ; [ 45.328° N, 72.186° W]; 29 Aug. 1937; G.E. Shewell leg.; compared with holotype by Vockeroth, 1960; 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 .

Description

Body blackish in ground colour, densely blue-grey pruinescent laterally, dark brown dorsally. Body length: 4–5 mm; wing length: 4.2–4.6 mm.

Male

HEAD ( Figs 13–15). Frontal vitta black, paler ventrally, matt; fronto-orbital plate black, grey pruinescent, with numerous black setulae. Chaetotaxy: 3 lateroclinate orbitals; 2 inclinate frontals; 1 ocellar, 1 inner vertical, 1 outer vertical; postocellar setae absent; row of dark postocular setae; 1 vibrissa, 1 strong subvibrissa. Gena silvery pruinescent, broad, depth below eye subequal to length of postpedicel; postgenal setae white to golden, soft, slightly shorter than width of postgena. Face, parafacial and occiput silvery pruinescent. Palpus yellow with long white setae. Proboscis with broad, shiny prementum, without setae. Antenna black; postpedicel rounded apically, 2 × as long as broad. Arista pubescent, bare on apical third.

THORAX ( Fig. 16). Dark brown with greyish postpropronotal lobe, lower notopleuron and scutellum; indistinct whitish vitta along acrostichal series anteriorly; pleura and mediotergite with greyish pruinescence. Acrostichals biserial, short, slender; 2+4 dorsocentrals; 1+2 intra-alars; 1+1 supra-alars; 1 postpronotal; 2 notopleurals, 1 postalar; scutellum with pair of strong apical setae and pair of strong basal setae; lateral margins and dorsal surface of scutellum apically with black setae and setulae. Pale proepisternal seta present. Proepimeral seta dark. Anepisternum with dark setae on posterior half and 1 long seta and several long thinner setae near posterior margin. Katepisternum with 1 strong seta in posterodorsal corner and numerous long yellow setulae.

LEGS ( Figs 16–17). Black, densely greyish pruinescence. Fore femur with 2 basal posteroventral setae extending well beyond dense setulae; row of long posterodorsal setae. Fore tibia with ventral apical spur, 1 anterodorsal at mid-length, usually 1 posteroventral seta near mid-length, 1 posteroventral seta beyond mid-length, 1 preapical posteroventral seta, slender, as long as basal width of fore femur and row of short, strong, black anteroventral setae proximal to spur. Mid femur with row of anterodorsal setae, with 1–2 posterior preapical setae. Mid tibia with 1 anterodorsal seta and 1 posterodorsal seta beyond mid-length; 1 preapical dorsal seta; 1 anteroventral and 1 posteroventral apical seta. Hind femur with row of anterodorsal setae and 1 anteroventral seta on apical fifth, all longer than width of femur. Hind tibia with 2 anterodorsal setae and 1 posterodorsal seta; 1 dorsal preapical seta and 1 anteroventral apical seta.

WING ( Fig. 16). Infuscate, without band; veins black; crossvein dm-m at right angles, not aligned with M 4; M 4 strong or weak beyond cell dm, one-quarter to one-half length of crossvein dm-m; CuA+CuP strong on basal two-thirds, weakened to wing margin. Calypteres pale brown; halter whitish yellow.

ABDOMEN. Similar to thorax, brownish dorsally, blue-greyish pruinescent laterally; with long slender setae. Sternite 4 wider than long ( Fig. 18). Sternite 5 broad, with pair of slightly C-shaped lobes; short setae on basal half with apex slightly flattened ( Fig. 18). Terminalia ( Figs 19–20): Epandrium rounded, broad. Cercus short, apical margin rounded in lateral view; cerci closely approximated medially, not projecting. Surstylus digitiform, tapered, elbowed beyond mid-length in posterior view; apex very narrow and rounded. Phallapodeme elongate, rod-shaped. Pregonite strongly recurved on distal half, with 1 short seta at mid-length; apex tapered to point with several short subapical setae. Postgonite gently arched with rounded apex. Ejaculatory apodeme anvil-shaped with expanded ejaculatory duct. Distiphallus narrow, tube-shaped.

Female

Similar to male except, palpus brown; terminalia not examined.

Distribution

This species is known from northeastern North America, recorded from Gaspésie ( Quebec) to Mt Washington ( New Hampshire) ( Fig. 61).