Ceratomerus oreas, Bradley J Sinclair, 2003

Bradley J Sinclair, 2003, Taxonomy, Phylogeny and Zoogeography of the Subfamily Ceratomerinae of Australia (Diptera: Empidoidea), Records of the Australian Museum 55, pp. 1-44 : 26-27

Ceratomerus oreas n.sp.

Figs. 56, 71–75

Type material. HOLOTYPE 3, “NSW[New South Wales, Australia]: Gloucester Tops/ el.1280; 19-xi–4-xii/ -1988; D.Bickel; mal-/ aise; Nothofagus for.”; “ HOLOTYPE / Ceratomerus / oreas / Sinclair [red label]” AMS K175248 . PARATYPES: New South Wales: 733, 4♀♀, same data as holotype ; 1♀, same locality as holotype, 14–19.xi.1988 ( AMS); 3 33, same locality as holotype, 4–30.xii.1988; 1 3, Barrington Tops NP, Gloucester Tops, Nothofagus , str., 1200 m, 21.xii.1993, BJS ( ZFMK) ; 533, 1♀, nr Gloucester Tops , 1290 m, Nothofagus , 14–19.xi.1988, DJB ( AMS, CNC) .

Diagnosis. Recognized by the distinct inflexion of R 2+3 around the stigma, dark pleura, long style and males have distinctive inflated, round epandrial lamellae, and broad, bilobed cercus.

Description. Wing length 3.3–3.6 mm, similar to C. attenuatus except as follows:

Male. Head. Postocellar bristles, short, one-third length of ocellar bristles. Antenna with length of scape one-fourth less than height of eye; postpedicel length less than height of head; three-segmented stylus longer than postpedicel; segment 8 elongate, 4× as long as wide.

Thorax. Pleura light brown.

Wing ( Fig. 56). R 2+3 running parallel and close to costa, strongly deflected around stigma.

Legs. Fore and mid coxae and ventral margin of femora pale yellow, remaining leg segments brown, darker towards tip. Fore femur slightly swollen, with av row of fine setae on basal half. First tarsomere two-thirds length of fore tibia.

Mid femur swollen similar to fore femur, with pv row of short, dark setae; basal half with av brush of short dark setae, increasing in length medially. Mid tibia slender with pv row of slender setae, longer than width of tibia; basal half with av row of short setae; ventroapically with row of short erect setae on apical fourth; 1 ad seta on basal third. First tarsomere 4 5 length of remaining 4 tarsomeres.

Hind femur with av row of fine setae, shorter than width of femur. Hind tibia with 2 erect dorsal setae on apical half; 3 erect ad setae.

Abdomen. S7 with transverse weakening on anterior third; posterior margin of S7 broadly membranous, with well sclerotized posterolateral margin, extending to S8; T8 bow-tie shaped, lacking ventral process.

Terminalia ( Figs. 72, 73). Hypandrium with pair of bilobed posterior processes; anterior lobe hooked posteriorly; postgonites erect, with broad base, strongly tapered to slender slightly curved tip; phallic processes absent; stout, blade-like, median phallic process somewhat arched anteriorly. Epandrial lamella greatly inflated laterally, round; fused ventrally to lateral wall of hypandrium. Surstylus with long, slender finger-shaped lobe. Subepandrial plate subrectangular, heavily sclerotized; more than half length of cercus. Cercus heavily sclerotized, short, broad, with bilobed apex; inner margin of anterior lobe with short, stout setae; posterior lobe with dense cluster of long stout setae, longer than width of lobe.

Female. Similar to male and female of C. attenuatus except as follows: Terminalia ( Fig. 75): T10 bearing single row of spine-like setae along posterior margin. Cercus broad, bearing spine-like setae, with short, slender marginal setae. Spermathecal receptacle oval, flattened, with short wide neck ( Fig. 74).

Distribution. This species is restricted to the type locality, an isolated patch of cool temperate rainforest dominated by Nothofagus ( Fig. 71).

Biology. All specimens were collected from or near cool, shaded mossy streams. The upper plateau of Gloucester Tops supports snow gum and grassland communities, while the gullies and saddles immediately below the plateau support stands of Nothofagus . It is in these sheltered wet forests where several species of Ceratomerus abide.

Etymology. The specific name is from the Latin oreas (mountain-nymph), referring to the high elevation of the type locality.