Roederiodes distinctus Chillcott, 1961

Sinclair, Bradley J., 2023, Revision of New World species of Roederiodes Coquillett (Diptera: Empididae: Clinocerinae), Zootaxa 5301 (3), pp. 336-364 : 342-343

Roederiodes distinctus Chillcott

( Figs 8, 20, 33)

Roederioides distincta Chillcott, 1961: 425 . Type locality: South St. Vrain Creek , Colorado, USA.

Roederiodes distinctus: Melander, 1965: 468 [catalogue]; Wilder, 1981: 419 [review]; Sinclair, 1995: 698 [species list].

Type material examined. PARATYPES: “ So. St. Vrain Creek [40°13′N 105°52′W]/ Boulder Co. Colo. / IX.8.[19]50”; “ W.W. Wirth / Collector”; PARATYPE / Roederioides ♀ / distincta/ Chillcott/ No. 7187 [yellow label, dissected]” (1 ♀, CNC; 1 ♀, USNM) .

Additional material examined. CANADA. Manitoba: Churchill, Eastern Ck, Launch Rd , 58°44.75′N 93°53.72′W, 12.vii.2009, JMC, CNC103452 , CNC103453 , CNC103454 (2 ♁, 1 ♀, barcoded, CNC) ; Cowan Ck , 4 km S & 2 km W Cowan [52°01′N 100°39′W], UTM grid: 14ULN855612, 9.ix.1986, R . G. Beutel & R . E. Roughley (1 ♀, CNC) . Northwest Territories: Mackenzie Basin, Trail River [62.10005°N 122.19286°W], 23.ix.1971, Basket 3, CNC Lot 71–741 (1 ♁, CNC); Fort Simpson, Pipeline Survey, MR2–35030772 DE [62°06′N 122°11′W] (1 ♁, 1 ♀, CNC); same data except, MR3-35120972 DE (4 ♁, 1 ♀, CNC); same data except, MR3–352606772 DE (1 ♁, CNC); Martin River , FWI, Pipeline Project , 20.vi.1972, MR1.35 DE (3 ♁, 3 ♀, CNC) . USA. Colorado: Larimer Co., Stonewall Ck, jct Hwy 287 [40.826170 -105.242309], 22.xi.1994, S. Fitzgerald (11 ♁, 4 ♀, CNC) . Utah: Wayne Co., Capitol Reef NP, Pleasant Ck [38°11′N 111°10′W], 2–7.viii.1993, JFM (1 ♁, CNC); Wayne Co. , Pleasant Ck, 5800 ft, 27.iv.1994, JFM (1?, CNC) .

Recognition. This species is distinguished by the distinct crossvein at apex of cell dm, longer than crossvein r-m, five distinct dorsocentral setae, scutellum and prescutellar depression with bluish pruinescence and clasping cercus tapered, with sharply pointed setae.

Redescription. Wing length 2.9–3.8 mm. Male. Face and gena with bluish pubescence. Ocellar setae divergent, subequal to pprn; vertical seta as long as ocellar seta. Antenna with short stylus, subequal to length of postpedicel; postpedicel onion-shaped, prolonged apically. Length of proboscis nearly subequal to head height.

Pleura, prescutellar depression and scutellum with blue pruinescence; acr very short, biserial, extending beyond second pair of dc, often to prescutellar depression; 5 dc, subequal, prescutellar seta longest; 1 pprn; 1 presut spal with several setulae; 2 npl with several setulae; 0 psut spal; 1 pal; 2 sctl and numerous short to long setulae on disc and margin; laterotergite with patch of pale setae; antepronotum with several setulae; lower proepisternum with pale setae.

Wing infuscate ( Fig. 8); cell dm pointed apically; M not acutely branched or coalesced for short distance; base of M 2 branch forming crossvein at apex of cell dm, longer than crossvein r-m.

Legs dark brown; coxae with bluish pruinescence. Hind tibia with distinct ventral setae, longer than half width of tibia.

Abdominal tergites with bluish pruinescence; bearing short black setae. Terminalia ( Fig. 20): Hypandrium slightly shorter than epandrium, apex somewhat truncate; without setae. Phallus slightly curved; membranous distiphallus without lateral extensions. Cercal plate with several long setae; clasping cercus long and tapered, longer than epandrium; inner face with stout, pointed setae on apical half; upper margin with stout, pointed setae.

Female. Similar to male.

Distribution. This species ranges from the Northwest Territories and Churchill, Manitoba to the Rocky Mountains of Colorado and the Wasatch Range of Utah ( Fig. 33).

Remarks. This species was originally described on the basis of female specimens. The male terminalia of R. distinctus was later illustrated by Wilder (1981, fig. 3), but the apex of the phallus was omitted. The shape of the clasping cercus is more accurately illustrated in Figure 20.

Although R. distinctus can be found in large, deep fast moving creeks in Colorado, the adults appear to prefer smaller, shallower creeks at elevations between 1830–2196 m (S.J. Fitzgerald 2020, pers. comm.).