Boreodromia bicolor (Loew)

Sinclair, Bradley J., 2008, Review of three little-known monotypic empidoid genera (Diptera: Empidoidea: Brachystomatidae), assigned to Trichopezinae, Zootaxa 1754, pp. 52-62 : 53-56

Boreodromia bicolor (Loew)

( Figs. 1–3, 8 )

Synamphotera bicolor Loew, 1863: 18 .

Sciodromia bicolor: Coquillett, 1900: 423 (Alaskan record). Synamphotera bicolor: Melander, 1902: 231 (redescription). Boreodromia bicolor: Coquillett, 1903: 247 (new genus).

Boreomyia bicolor: Aldrich, 1905: 316 (catalogue record, genus name error).

Type material examined. LECTOTYPE (here designated), male labelled: “524”; “Loew.”; “ Type / 13088 [red label with upper white border] [only thorax and abdomen remaining]” ( MCZ). My lectotype label “LEC- TOTYPE/ of Synamphotera / bicolor Loew / des. B.J. Sinclair 1992 [red label]” has been attached to this specimen.

PARALECTOTYPE: Same data as lectotype [only thorax and abdomen remaining] (1 &, MCZ). My paralectotype label has additionally been attached to this specimen.

Additional material examined (440 specimens). CANADA. British Columbia: Abbotsford, 27.vi.1952, W.R.M. Mason ( CNC); Bear Lk, Crooked R. Prov. Pk, 16.viii.1978, PHA ( USNM); Culculz Lk., 2,20,25. vii.1948, H.R. Foxlee ( CNC); Cassiar Hwy, 353 mi, Moose Meadows Resort, 2.viii.1996, PHA ( USNM); Hagensborg, 12.vii.1992, A. Borkent ( CNC); Hope, 15 mi E, 12.vii.1973, H.J. Teskey ( CNC); Lk. Errock, nr Deroche, 2.vi.1953, W.R.M. Mason ( CNC); Lund, 7 km SE, 16.viii.1988, A. Borkent ( CNC); Mission City, 5–22.vi., 2.vii.1953, W.R.M. Mason ( CNC); Mt. Allard, 23 mi N Terrace, 11.viii.1960, CHM ( CNC); Mt. Thornhill, nr Terrace, 30.vii., 8.viii.1960, BH, CHM ( CNC); Prince Rupert, 18.vii.1960, W.R. Richards ( CNC); Queen Charlotte Is., Moresby Is., Sand spit, 0–50 m, vi.1978, N.L.H. Krauss ( USNM); Queen Charlotte Is., Graham Is., Rennell Sound, 16.vii.1988, S.A. Marshall ( CNC); Kelkirk Mtns, Downie Ck, 14.viii.1905, J.Ch. Bradley ( CUIC); Terrace, 17–18.vii., 2–11.viii.1960, W.R. Richards ( CNC); Terrace, airport area, 3–4.viii.1960, BH, CHM ( CNC); Terrace, 32 mi E, 11.vi., 5,13. vii.1960, J.G. Chillcott, BH ( CNC); Terrace, 35 mi W, Exchamsiks R, 9.vii.1960, J.G. Chillcott ( CNC); Vancouver Is., Courtney, 0–50 m, 1.vii.1978, N.L.H. Krauss ( USNM); Vancouver Is., Deep Bay, 16.vi.1955, R. Coyles ( CNC); Vancouver, Pt. Grey, 8.viii.1972, 10.vii.1988, J.R. Vockeroth ( CNC); New Westminster, 8.viii.1917 ( USNM). USA. Alaska: Cold Bay, 163°W, tundra, 26.vii., 13–18.viii.1952, W.R. Mason ( CNC); Hyder, 5.viii.1996, PHA ( USNM); Popof Is., 8,10. vii.1899, Harriman Expedition ’99, T. Kincaid ( USNM); Valdez, 3 mi W, 24.viii.1948, R.I. Sailer ( USNM); Valdez Glacier Cpgd, 2.viii.1978, PHA ( USNM). California: Arcata, 8.vii.1954, M.T. James ( CUIC); Humboldt Co., Mad R. Beach, 14.viii.1948, W.W. Wirth ( USNM); Marin Co., Inverness, 4.viii.1968, D.D. Munroe ( CNC); Mendocino Co., Mendocino, 9.viii.1963, PHA ( USNM); San Francisco City, Lk.

Merced, 30.vii.1966, 11.vii.1967, PHA ( USNM). Oregon: Boyer, 26.v.1935 ( AMNH); Curry Co., Cape Blanco, 29.vi.1972, G. Steyskal ( USNM); Lane Co., Siuslaw NF, 3 mi S Yachats, Gwynn Ck trail & Rock Ck, 15.vii.1989, B.J. Sinclair ( CNC); Marsh Field, vi.1927, J.M. Aldrich ( USNM); Mt. Hood, Hood Rapids, 29.vii.1921, ALM ( USNM); Mt. Hood, Nooksack R, 11.viii.1925, ALM ( USNM); Smith R., 8.vii.1930, J.M. Aldrich ( USNM). Washington: Ana Cortes, 21.vii.1960, F.C. Harmston ( USNM); Brinnon, Forest Res., 27.vii.1917, ALM ( USNM); Burton, 19.viii.1910 ( USNM); Canyon Ck, 26.vii.1925, ALM ( USNM); Everett, Lk. Stephane, 3.viii.1917, ALM ( USNM); Ilwaco, vii., 27.viii.1917, 12, 28.vii.1925, ALM ( CUIC, USNM), 18, 29.vi., 7.vii.1918, A. Spuler ( WSU); Lilliwaup, 18.viii.1921, ALM ( USNM); Lummi Is., 18.vi.1944, R.D. Shenefelt ( WSU); Mt. Constitution, 28,31. vii.1909 ( USNM); Mt. Rainier, Tahoma Fork, 25.vii.1922, ALM ( USNM); Mt. Vernon, 3.vii.1924, ALM ( USNM); Nahcotta, 24,30.viii.1954, 8.vii.1955 ( WSU); Ocean Pk, 9– 10, 17.viii.1950, 28.vi., 13.vii.1954, 16.vii.1957, M.T. James ( WSU); Pacific Co., Ft Canby SP, nr. Ilwaco, 16.vii.1977, W.J. Turner ( USNM); Piedmont, Lk. Crescent, 24.vii.1917, ALM ( USNM); Pt. Gamble, 16.viii.1910 ( USNM); Quilcene, 24.vii.1917, ALM ( USNM); Sequin Bay, 3.xi.1934, ALM ( USNM); Sultan, 1.viii.1917, ALM ( USNM); Tokeland, 18.vii.1917, ALM ( USNM); Tulalip, 3.viii.1917, ALM ( USNM); Vashon, 18.viii.1910 ( USNM).

Recognition. This genus and species is readily distinguished from other North American empidoids by its shiny abdomen, bicoloured antenna, truncate cell cua and simple or unbranched R4+5.

Description. Male ( Fig. 1). Dichoptic, eyes with very short and sparse ommatrichia, lower facets becoming larger; ocellar bristles pale and slender. Antennae inserted in middle of head; scape and pedicel yellow, stylus brown; postpedicel long and tapered, bearing long pubescence; stylus three-articled, basal article small, square-shaped; second article one-third length of postpedicel; apical article (segment 10) peg-like and longer than basal article. Gena very narrow, not divided. Proboscis pale, yellowish, length approximately subequal to height of head; labrum long and stout, with 5 apparent apical epipharyngeal blades; labium long; labellum not held in horizontal position, bearing 9–10 pseudotracheae; lacinia free, equal in length to palpus; hypopharynx long, slender, equal in length to labrum. Palpus long and pointed, half-length of proboscis, bearing pale setae.

Prosternum fused to proepisternum. Pleura light brown, paler on precoxal bridge, with sparse pruinescence; scutum dark brown, mostly covered by pruinescence except outside of dc row at mid-length; postpronotal lobe pale. All thoracic setae pale; acrostichals uniserial, extending to prescutellar depression; approximately 10 dc; only setulae on postpronotal lobe; 1 short presut spal; 2 npl, lower slender and short; 2 short psut spal; 1 pal; 4 sctl. Laterotergite bare; antepronotum with several pale setulae.

Wing (length 3.9–4.2 mm) clear with microtrichia; stigma faint, elongate; single short basal costal seta. Costa circumambient; R4+5 simple; Sc evanescent; cell dm produced apically; cell cua (= anal cell) truncate; CuP+CuA (= A1+CuA2) faint, long nearly reaching wing margin. Calypters with fringe of pale setae. Haltere very pale.

Legs, including coxae, yellow, apical two tarsomeres dark. Empodium bristleform; pulvilli pad-like. Fore femur with long, white pile beneath; mid femur with posteroventral row of long setae. Fore tibia with anterior apical comb; hind tibia with posterior apical comb. Fifth tarsomere lacking dorsoapical extension.

Abdomen dark brown, shiny. T8 well developed, narrowed mid-dorsally. Terminalia ( Fig. 2 ): epandrium enclosing and fused to hypandrium ventrally. Hypandrium reduced, narrow, with pointed apex; bearing pair of phallic guides, extending half-length of abdomen. Phallus filamentous, extended length of abdomen, emerging at apex of hypandrium; base of phallus with double articulated ejaculatory apodeme, moved by set of stout adductor muscles; phallus supported by long forked phallic guide. Cercus not subdivided, held erect. Surstylus large, ear-like, positioned at posterodorsal margin of epandrium.

Female. Similar to male except as follows: all femora with long, white pile beneath; fore and mid tibiae with stout dark erect setae beneath. Segment 10 and cerci retracted within T8 ( Fig. 3 ). Spermatheca very elongate, lightly sclerotized tube, longer than abdomen; surface covered by erect pubescence. Genital fork strongly sclerotized, U-shaped and darkly pigmented.

Distribution. Boreodromia bicolor was originally described from Sitka, Alaska, from material collected by Sahlberg ( Loew 1863). This species is rather localized and occurs along the Pacific coast of North America ( Fig. 8 ), from Alaska to California ( Melander 1928), including the Queen Charlotte Islands (or Haida Gwaii). This type of distribution is known as a Pacific coastal-centred element (see Kavanaugh 1988).

Bionomics. Boreodromia bicolor has been collected along streams and riparian regions, coastal rainforests and tundra (some Alaskan records). The immature stages of this genus are unknown.

Remarks. Boreodromia is a monotypic genus that has been very difficult to place into the existing major lineages of the Empidoidea. Until the revision by Sinclair (1995), this genus had been assigned to the Clinocerinae , presumably due to the narrow wings and truncate or slightly rounded anal cell. Sinclair (1995) transferred Boreodromia to the Trichopezinae , now assigned to the family Brachystomatidae ( Sinclair & Cumming 2006) . There are striking similarities between the male terminalia of Boreodromia and the Nearctic species of Apalocnemis Philippi described by Melander (1946). Both taxa share the following apomorphies: hypandrium and epandrium fused; elongate, thread-like phallus; erect, unmodified male cerci; ear-like surstyli; and elongate, tube-shaped spermatheca (a narrow tubular spermatheca, lacking terminal sclerotized receptacle, is partially visible in available specimens of Nearctic Apalocnemis species; however, verification in additional specimens is required). The male terminalia of these taxa are also similar to two undescribed species collected during the winter months in California. The latter two species are similar to the genus Gloma Meigen on the basis of their similarly modified postpedicel.

The male and female terminalia of B. bicolor are here described and illustrated for the first time. A coloured habitus drawing of this species is found in Melander (1928, fig. 20). This genus can be identified using the key to genera of North American Empididae by Steyskal & Knutson (1981).

Figures

FIGURE 8. Known distribution of Boreodromia bicolor. Arrow points out also locality of Ceratempis longicornis.

FIGURES 2 – 7. Male and female terminalia. 2. Boreodromia bicolor, male, lateral view. 3. B. bicolor, female, lateral view. 4. Ceratempis longicornis, male, lateral view. 5. C. longicornis, male, hypandrium and phallus, dorsal view. 6. C. longicornis, female, dorsal view. 7. C. longicornis, female, tergum 7 removed, lateral view. Abbreviations: apod – apodeme, cerc – cercus, ej apod – ejaculatory apodeme, epand – epandrium, hypd – hypandrium, ph – phallus, ph gd – phallic guide, S – sternum, spmth – spermatheca, sur – surstylus, T – tergum. Scale bar = 0.1 mm.