Dasysyrphus occidualis Locke & Skevington, 2013

Locke, Michelle M. & Skevington, Jeffrey H., 2013, Revision of Nearctic <i> Dasysyrphus </ i> Enderlein (Diptera: Syrphidae), Zootaxa 3660 (1), pp. 1-80 : 52-54

Dasysyrphus occidualis Locke & Skevington sp. nov.

Figures: 12A–E, 21B

Synonyms and References:

Syrphus amalopis Osten Sacken :

Williston 1887: 69 (in part; description)

Metasyrphus amalopis :

Fluke 1933: 110 (in part; key and redescription)

Dasysyrphus amalopis :

Stone et al. 1965: 563 (in part; catalogue)

Vockeroth 1992: 63 (in part; key and redescription)

Diagnosis: Abdominal maculae do not meet abdominal margin; maculae on tergites 3&4 are constricted medially and are either divided or not ( Figs 12A–C ). Wings cell br usually with a small bare area above base of spurious vein ( Fig. 12E ). Surstylus with a prominent posterolateral edge ( Fig. 12D ). Similar to D. amalopis , but D. amalopis has maculae on tergites 3&4 usually undivided ( Fig. 5A ), cell br densely microtrichose and does not have a prominent posterolateral edge on the surstylus ( Fig. 5C ). Male genitalia should be used to reliably differentiate between these two species. There is a range of overlap in southern Yukon where it may not be possible to distinguish between females of these two species due to variations in the aforementioned characters.

Description:

Body Length: 8.0– 11mm; Wing Length: 7.2–10.7mm

Head: Frons dark with light pollenose fascia (in males it runs along ventral edge of where eyes meet, in females it is continuous, ⅓–½ the length between the antennae and ocelli) with dark pile; face light with dark vitta <¼–⅓ the width of the face, usually not reaching antennal socket, if it does then narrowly so, face with dark pile; gena dark with dark pile ventral to the eye and light pile elsewhere; occiput dark, covered in light pollen, pile light; scape, pedicel and flagellomere dark.

Thorax: Scutum dark, may appear shiny or metallic, pile light anteriorly and dark posteriorly (amount varies); scutellum light to dark with darker lateral edges, some light pile along anterior edge and dark pile elsewhere; wing densely microtrichose, cell br usually with small bare areas at above base of spurious vein, r 1 sometimes bare at base and cup sometimes bare in areas along vein CuP ( Fig. 12E ); haltere light; pro- and mesofemora ½–¾ dark basially, ¼–½ light apically, metafemur ¾ dark basially, ¼ light apically, tibiae variable from all light to slightly darkened apically to ¾ dark apically, tarsi light with dark anterior side to all dark.

Abdomen: Maculae on tergite 2 large, ⅓–<½ the width of tergite 2, and oval with constriction medially (sometimes just slight constriction), maculae on tergites 3&4 are oblique and constricted medially, usually completely dividing maculae into four spots, if not completely divided then maculae on tergite 4 usually more constricted that on tergite three and almost divided, maculae do not reach abdominal margin ( Figs 12A–C ); sternite 2 is light with a dark triangular to straight macula connecting with the lateral edges of the sternite, sternites 3 & 4 are light with dark fasciae of varying thickness.

Male Genitalia: Surstylus more or less triangular in shape in lateral view, flattened posteriorly with prominent posterolateral edge, long pile on dorsal, laterodorsal and posterodorsal sides, row of spines on posteromedial edge; cercus oval with long pile over entire surface; gonostylus boot-shaped with pointed projection on posterodorsal surface that projects dorsally, pile on dorsal surface; basiphallus elongate, basally bent at about a 135 degree angle towards the anterodorsum, apical end curved ventrally with a widened apex and is partly membranous dorsally, with spines on posterodorsal side, apex; distiphallus elongate, apical end flared out into horn, which is mostly sclerotized but membranous at apex with minute setulae dorsally, basally bent towards dorsum and enlarged ventrally at bend ( Fig. 12D ).

Intraspecific variation: The maculae on tergites 3 & 4 are often divided ( Fig. 12B ). If not completely divided then maculae on tergite 4 usually more constricted that on tergite three and almost divided. Can have maculae on tergites 3 & 4 entire, but this less common ( Fig. 12A ). Wing densely microtrichose, except for cell br, which is usually bare above base of spurious vein, sometimes only in very tiny areas with one or two microtrichia missing, r 1 sometimes bare of microtrichia at base and cup sometimes bare in areas along vein CuP ( Fig 12E ).

Etymology: From the Latin occidualis , meaning western.

Distribution: Western Canada (AB, BC, YT) and western USA (AK, CO, WA, WY) ( Fig. 21B ).

Ecology: Collected from May–August, but more frequently collected in July. Collected at elevations of 613– 3658m. Habitats listed on labels include “outlet marsh”, “sedge fen” and “subalpine”.

Discussion: Until now, D. occidualis has been hidden within D. amalopis . With an absence of distinguishing external morphological characters, additional data were necessary to illuminate cryptic species such as this. In this study, COI DNA first highlighted the existence of two distinctly different genetic clusters within amalopis . Upon further inspection of the specimens, the male genitalia showed a prominent posterolateral edge on the surstylus ( Fig. 12D ), which amalopis does not have ( Fig. 5C ). When their geographic ranges were studied it was found that specimens of occidualis were only located in western Canada and the US (from Alaska to Colorado), while amalopis was found only in northern Canada. There is an overlap zone in southern Yukon so specimens in this area must be carefully studied to make the correct species determination.

Type Material: “ USA: WA: Mt. Baker-/ Snoqualmie NF: Mt. Baker :/ SilverFirCampground; 2012ft. / 48.904950°N, 121.697917°W;/ 8.vii.2010; M.M.Locke ”, “ J. Skevington / Specimen #/ 23708”, “ HOLOTYPE / Dasysyrphus / occidualis/ Locke &/ Skevington”, ♂, deposited in the Canadian Collection if Insects, Arachnids and Nematodes ( CNC), Ottawa, Ontario , Canada.

Material Examined:

Canada: Alberta: Kananaskis, Forest Experimental Station Seebe , [51.100879, -115.087692], 15.vi.1968, ♀, CNCD 5014 , H.J. Teskey ( CNC). BANFF NATIONAL PARK : Banff , [51.180275, -115.568433], 15.vii.1922, 3♂, CNCD 13621–13623 , C.B.D. Garrett ( CNC); ♀, JSS 19432, N.B. Sanson ( CNC); 11.vii.1951, ♀, CNCD 13619 , ( CNC) . British Columbia: CATHEDRAL PROV. PARK : Glacier Lake , [49.055785, -120.207299], 6.vii.1986, ♀, RBCM ENT 9882357 , R . A. Cannings ( RBCM); fen, Lk. of the Woods trail, [49.08, -120.18], 26.vii.1988, ♀, JSS 20186, S.G. Cannings ( UBCZ). Squamish , Diamond Head Trail , [49.811126, -123.07434], 1219m, 11.viii.1953, ♀, CNCD 13610 , W. R. M. Mason ( CNC). Duffey L. Blowdown Cr., lake S. of Gott Peak , [50.40416667, - 122.3416667], 21.vii.1988, ♀, RBCM ENT 9918197 , C.S. Guppy ( RBCM). Cornwall Hills Lookout , [50.7, - 121.5], 2037m, 14.vi.1989, ♂, RBCM ENT 990626 , R . A. Cannings & C.S. Guppy ( RBCM). KOOTENAY NATIONAL PARK : Daer-Pitts Aspen Control 2, [50.776662, -115.936917], 17.vi.–2.vii.2000, 2♂, CNCD 30908 , 30909 , ♀, CNCD 30903 , G. Gareau ( CNC); Floe Lake , [51.054, -116.137], 1981m, 9.viii.1955, ♀, CNCD 13611 , J. R. W. McGillis ( CNC). MOUNT REVELSTOKE NATIONAL PARK : [51.035979, -118.142509], 1828m, 26.vii.1952, ♀, CNCD 13612 , G.P. Holland ( CNC); 15.viii.1952, ♀, CNCD 13613 , G.J. Spencer ( CNC); Mount Harry , [51.035979, -118.142509], 2073m, 8.viii.1952, ♀, CNCD 13614 , G.J. Spencer ( CNC); Mt. Revelstoke , [51.05, - 118.1333333], 1829m, 7.viii.1952, ♀, RBCM ENT 99188105 , G.P. Holland ( RBCM); Eva Lake Trail , [51.079905, -118.108837], 1828m, 6.viii.1952, ♀, CNCD 13615 , G.J. Spencer ( CNC). SKENNA- QUEEN CHARLOTTE R . D.: Tlell, Queen Charlotte Islands , [53.562591, -131.93235], 25.v.1957, ♂, CNCD 13620 , E.E. MacDougall ( CNC). NORTHERN ROCKIES R . D.: Summit Lake, Mile 392 of Alaska Highway , [58.648201, -124.666912], 1372m, 1.vii.1959, ♀, CNCD 13603 , R . E. Leech ( CNC); 1.vii.1959, ♀, CNCD 13605 , 2–4.vii.1959, 3♀, CNCD 13606– 13608 , 6.vii.1959, ♀, CNCD 13604 , E.E. MacDougall ( CNC). Ft. Nelson , [58.804594, -122.697436], 4.vii.1949, ♀, JSS 19993, J.K. Morie ( UBCZ). Liard R . hotsprings, [59.425991, -126.096398], 23.vii.1987, 3♀, JSS 20176– 20178, S.G. Cannings ( UBCZ). Fireside , [59.666676, -127.14242], 24.v.1980, CNCD 60083 , Bruce Gill ( CNC). 7 miles N Lions Bay , 18.v.1979, ♂, CNCD 5463 , G.F. Hevel ( CNC). Spanish Hills, Galiano Island , 10.v.1980, CNCD 60094 , G.G.E. Scudder ( CNC) . Yukon Territory: Carcross Dunes at Bennett L. beach, [60.17066, -134.71809], 666m, 25.vi.2009, ♀, JSS 20819, Lee Mennell ( RBCM). Takhini R ., west dunes 6.8km NNE of Kusawa L. outlet, [60.66824, -136.07664], 19.vi.2009, ♀, JSS 20820, S. Cannings ( RBCM). Sheldon Lake , [62.616763, - 131.266603], 914m, 21.vii.1960, ♀, CNCD 13561 , J.E.H. Martin ( CNC). DEMPSTER HIGHWAY: North Klondike River, Km 64 [64.45056, -138.218356], 9.vi.1980, ♂, JSS 18376, R . J. Cannings ( CNC) . United States of America: Alaska: MATANUSKA- SUSITNA CO.: Matanuska, [61.541945, -149.229674], 29.v.1944, ♀, JSS 19431, J. Chamberlin ( CNC). Nome Area, Mile 17 of Kougarok Road , [64.70611111, -165.2972222], 26–28.vi.2005, ♀, CNCD 30899 , J.& R. Skevington ( CNC) . Colorado: Pike's Peak Summit , [38.840342, -105.045006], 14.viii.1977, ♀, USNM ENT 258091 , A.B. Gurney ( USNM). GUNNISON CO.: Ragged Mountain , [39.118885, -107.407678], 20.vi.1950, ♂, CNCD 26345 , C.A. Downing ( CNC). CLEAR CREEK CO.: Mount Evans , [39.645575, -105.594897] 22.vii.1961, ♀, CNCD 26335 , J.G. Chillcott ( CNC); 3.viii.1961, 2♀, CNCD 26330 , 26331 , S.M. Clark ( CNC); 3.viii.1961, 2♀, CNCD 26332 , 26333 , W. R. M. Mason ( CNC); 4.viii.1961, ♂, CNCD 26342 , J. R. Stainer ( CNC); 10.viii.1961, ♀, CNCD 26334 , C.H. Mann ( CNC); Timberline, Mount Evans , 3566m, 22.vii.1961, ♀, CNCD 26336 , C.H. Mann ( CNC); 22.vii.1961, ♀, CNCD 26337 , B.H. Poole ( CNC); Echo Lake, Mt. Evans , [39.658085, - 105.6035], 3231m, 22.vii.1961, ♀, CNCD 26338 , J.G. Chillcott ( CNC); Doolittle Ranch, Mt. Evans , [39.675739, - 105.601348], 2987m, 12.viii.1961, ♀, CNCD 26339 , J. R. Stainer ( CNC); Guanella Pass , [39.594992, - 105.711109], 3536m, 14.vii.1961, ♀, CNCD 26340 , S.M. Clark ( CNC). Brainard Lake Rec. Area 4mi W of Ward Colorado, [40.069261, -105.584835], 11.viii.1952, ♀, JSS 21103, R. R . Dreisbach ( MSUC); 21.viii.1977, 2♂, USNM ENT 258062 , 258063 , A.G. Lavallee ( USNM). Cameron Pass , [40.520816, -118.227668], 28.vii.1954, ♂, OSAC 133386 , Chas. L. Fluke ( OSAC). North Park , [40.73, -106.18], 1.vii.1932, ♀, JSS 20665, ( CSUC) . Washington: MT. RANIER NATIONAL PARK : Paradise Valley, [46.782709, -121.727952], 15.vii.1920, ♂, JSS 23880, 18.vii.1920, 7♂, JSS 23722, 23888, 23889, 23893, 23894, 23900, 23904, 19.vii.1920, 2♂, JSS 23886, 23887, ♀, JSS 23718, 25.vii.1920, ♂, JSS 23883, E.C. Van Dyke ( CAS); 18.vii.1920, ♂, JSS 20613, E.C. Van Dyke ( EMEC); Carbon River near Ranger station , [46.85, -121.75], 15.viii.1999, ♀, JSS 20681, B. Kondratieff ( CSUC); Louis Lake , Fryingpan Cr. , Sunrise Rd. , [46.85, -121.75], 17.vi.2004, ♂, JSS 20804, B. Kondratieff, J. Schmidt, J. Owens ( CSUC). Seattle, [47.60621, -122.332071], 16.vi.1901, ♀, OSAC 133444 , ( OSAC). MT. BAKER- SNOQUALMIE NATIONAL FOREST : Mt. Baker, Picture Lake, [48.866217, -121.676533], 1273m, 7.vii.2010, ♂, JSS 23706, ♀, JSS 24625, A. Young ( DEBU); Silver Fir Campground , [48.90495, 121.697917], 613m, 8.vii.2010, ♂, JSS 23708, 9.vii.2010, ♀, CNCD 35311 , 60043 , M.M. Locke ( CNC); 9.vii.2010, CNCD 60046 , CNCD 60047 , A. Young ( CNC) . Wyoming: Wyoming , [43.084281, -107.556417], 1952, ♀, CNCD 26329 , F.M. Hull ( CNC). Yellowstone National Park , [44.587719, -110.537673], 20.vii.1925, ♂, CNCD 26343 , A.A. Nichol ( CNC) .

Figures

FIGURE 5. Dasysyrphus amalopis: A: female (CNCD 13616) dorsal habitus, T = tergite; B: female (CNCD 13616) lateral habitus; C: lateral view of male (CNCD 9607) genitalia; D: wing base (CNCD 13587). Dorsal and lateral habitus scale bar = 1mm, genitalia and wing scale bar = 500µm.

FIGURE 12. Dasysyrphus occidualis: A: female (CNCD 60043) dorsal habitus; B: male (OSU 0000133386) dorsal habitus; C: male (OSU 0000133386) lateral habitus; D: lateral view of male (JSS 20804) genitalia; E: wing base (CNCD 60046). Dorsal and lateral habitus scale bar = 1mm, genitalia and wing scale bar = 500µm.

FIGURE 21. Dasysyrphus species range maps (symbols indicate specimen point data). A: D. lotus (squares) and D. nigricornis (circles); B: D. occidualis; C: D. pacificus; D: D. pauxillus (circles) and D. pinastri (squares).