Parathalassius wheeleri,

Cumming, Jeffrey M., 2017, Revision of the Nearctic Parathalassius Mik (Diptera: Dolichopodidae: Parathalassiinae), with a review of the world fauna, Zootaxa 4314 (1), pp. 1-64: 52-58

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Parathalassius wheeleri

sp. nov.

Parathalassius wheeleri  sp. nov.

( Figs 25View FIGURES 23 – 28, 39View FIGURES 38 – 47, 57View FIGURES 56 – 67, 72View FIGURES 72 – 75, 93–94View FIGURES 80 – 94, 105–106View FIGURES 103 – 110, 122View FIGURES 121 – 126, 153View FIGURES 152 – 153)

Type material. HOLOTYPE ♂ labelled: “USA: OR: Lane Co., Suislaw / North Jetty , nr. Florence,/ 44°01′07.0″N 124°08′12.6″W / 7.vii.2014, swept dunes &/ beach grass ( Ammophila  )/ S.E. Brooks ”; “ HOLOTYPE / Parathalassius wheeleri  / Brooks & Cumming [red label]” (CNC)GoogleMaps  . PARATYPES: USA: Oregon: same data as holotype (4♂, 3♀, CNC)GoogleMaps  ; same data as holotype except, CNC487199 (1♂, barcoded, CNC)GoogleMaps  ; same data as holotype except, J.M. Cumming (3♂, 2♀, CNC)GoogleMaps  ; same data except, CNC487200 (1♀, barcode-associated, CNC)GoogleMaps  ; same data except, 8.vii.2014 (2♂, 5♀, CNC)GoogleMaps  .

Other material examined. CANADA: British Columbia: Haida Gwaii, Graham Is. , 3km N Tlell [ca. 53°33′37″N 131°55′39″W], 13.vii.1988, meadow behind dunes, T.A. Wheeler, (1♀, CNC)GoogleMaps  ; Vancouver Is., Brooks Peninsula, Cape Cook Lagoon , 50°12′N 127°48′W, 2.viii.1981, fall trap sand dunes (4♂, 6♀, UBCZ)GoogleMaps  ; same data except, 5.viii.1981 (8♂, 1♀, UBCZ)GoogleMaps  ; same data except, 7.viii.1981 (3♂, UBCZ)GoogleMaps  ; same data except, 2.viii.1981, CNC DIPTERA  #103908 (1♂, UBCZ)GoogleMaps  . USA: California: Del Norte County: Smith River Dunes [ca. 41°55′03″N 124°12′17″W], (7♂, 8♀, EMEC)GoogleMaps  ; Humboldt County: Clam Beach [ca. 40°59′40″N 124°06′58″W],, A.L. Melander (1♂, 1♀, USNM)GoogleMaps  ; Clam Beach Co. Park N of Eureka , 15.v.1978, D.D. Wilder (8♂, 8♀, CAS)  ; Fieldbrook [ca. 40°57′32″N 124°07′32″W], 31.v.1903, H.S. Barber (1♀, USNM)GoogleMaps  ; Lanphere-Christensen Dunes [ca. 40°53′09″N 124°08′47″W],, M.E. Buegler (10♂, 14♀, EMEC)GoogleMaps  ; same data except, 4 mi. W Arcata , 26.vii.1975, M.E. Buegler & E.I. Schlinger (8♂, 7♀, EMEC)GoogleMaps  ; Samoa Peninsula, Samoa Dunes Recreation Area , 40°45′41″N 124°13′37″W, 21.v.2009, J.M. Cumming (13♂, 23♀, CNC; 2♂, 2♀, CSCA)GoogleMaps  ; same data except, swept dune vegetation (11♂, 9♀, CNC)GoogleMaps  ; same data except, S.E. Brooks (30♂, 28♀, CNC)GoogleMaps  ; same data except, CNC DIPTERA  #’s 103904, 103905, 103913 (2♂, 1♀, respectively, barcoded, CNC)GoogleMaps  ; Samoa dunes,, D. Levin, LACM ENT 337200View Materials (1♂, LACM)  . Oregon: Lane County: Heceta Beach , 44°02′14.7″N 124°07′57.2″W, 7.vii.2014, swept dunes & beach grass ( Ammophila  ), J.M. Cumming (1♂, CNC)GoogleMaps  ; same data except, CNC5View Materials 88229 (1♂, barcoded, CNC)GoogleMaps  ; Lincoln County: South Beach State Park , 44°36′05.6″N 124°03′54.0″W, 3.vii.2014, swept dunes & beach grass ( Ammophila  ), J.M. Cumming (2♂, 2♀, CNC)GoogleMaps  ; same data except, CNC487198View Materials (1♀, barcodeassociated, CNC)GoogleMaps  . Washington: Grays Harbor County: Copalis [ca. 47°06′37″N 124°11′6″W], 14.viii.1921, A.L. Melander (1♀, USNM)GoogleMaps  ; Pacific County: Tokeland [ca. 46°42′21″N 124°00′08″W], 18.vii.1917, A.L. Melander (1♀, USNM)GoogleMaps  ; Cape Disappointment State Park nr. Ilwaco, Benson Beach, 46°16′20.4″N 124°04′25.4″W, 1.vii.2014, swept dunes & beach grass ( Ammophila  ), S.E. Brooks (1♂, 1♀, CNC)GoogleMaps  ; same data except, CNC487108View Materials (1♀, barcode-associated, CNC)GoogleMaps  ; same data except, 2.vii.2014, CNC588230View Materials (1♂, barcoded, CNC)GoogleMaps  ; same data except, 1.vii.2014, J.M. Cumming (1♀, CNC)GoogleMaps  ; same data except, CNC588231View Materials (1♀, barcode-associated, CNC)GoogleMaps  ; Ilwaco, Cape Disappointment , 23.vii.1993, H. Ulrich (3♂, 6♀, ZFMK)GoogleMaps  ; same data except, 24.vii.1993 (3♂, ZFMK)GoogleMaps  ; same data except, 25.vii.1993 (1♀, ZFMK)GoogleMaps  ; same data except, Benson Beach , dunes, 5.viii.1994 (10♂, 16♀, ZFMK)GoogleMaps  ; same data except, 9.viii.1994 (29♂, 18♀, ZFMK)GoogleMaps  ; same data except, 10.viii.1994, sandy beach, (5♀, ZFMK)GoogleMaps  ; Ilwaco , vii.1917, A.L. Melander (1♂, USNM)  .

Diagnosis. This relatively small species is characterized by a subtriangular antennal postpedicel, longer lower male ommatrichia, 2 notopleural bristles, hyaline wing, and relatively dark legs. Parathalassius wheeleri  is very similar to P. aldrichi  , but males can be distinguished from this more southern species by the shape of the apex of the right cercus and dorsal lobe of the left surstylus, as well as the more basal position of the dentiform process of the phallus.

Description. Male: Body length 1.7–2.1 mm, wing length 1.7–1.9 mm. Dark brown ground colour covered mostly with dense greyish-white pruinosity. Setae of body and legs white. Head ( Fig. 25View FIGURES 23 – 28): Eyes with ommatrichia of lower third distinctly longer and slightly flattened, forming dense reflective mat of whitish coloured hair. Face and clypeus concolourous with greyish-white frons and vertex. Face narrowest at middle, about 2.5X width of anterior ocellus. Gena and postgena with moderately long white setae, forming short beard flanking mouthparts. Antenna ( Fig. 39View FIGURES 38 – 47) including arista-like stylus, entirely dark brown; postpedicel subtriangular, 1.5–1.6X longer than wide; arista-like stylus of medium length, about 1.5X length of postpedicel. Palpus with 7–8 setae on outer surface of apical half. Thorax: Acrostichal setulae primarily biserial; 6–7 dorsocentral bristles, 0 presutural intra-alar bristles, 1 presutural supra-alar (posthumeral) bristle, 2–3 postsutural supra-alar bristles, 2 notopleural bristles. Scutellum with 2–3 pairs of bristles. Legs: Foreleg: Dark grey, pale at knee and extreme apex of tibia, tarsus pale brown. Coxa with short pale setae on anterior surface. Femur with moderately long setae on posterior surface. Tibia and tarsus with setulae; tarsomeres 1–2 not dilated. Midleg: Dark grey, pale only at knee, tarsus greyish-brown. Femur with anterodorsal setae most prominent. Tibia with pair of apicoventral bristles. Tarsomeres 1–4 each with several dark spine-like apicoventral setae. Hindleg: Dark grey, femur dark brown posteriorly, pale at knee, tarsus pale brown to greyish-brown. Femur with anteroventral row of setae prominent. Tibia with anterodorsal and anteroventral rows of setae of moderate length, subequal or slightly longer than width of tibia. Tarsus subequal in length to tibia with short setae and setulae; tarsomere 1 shorter than combined length of tarsomeres 2–4; tarsomeres 1–4 lacking peg-like or thickened setae dorsally; tarsomere 2 longer than tarsomere 3; tarsomere 3 longer than tarsomere 4; tarsomere 5 subequal in length to tarsomere 3. Wing ( Fig. 57View FIGURES 56 – 67): Hyaline with dark brown veins. Cell dm produced apically, dm-m crossvein nearly straight. Vein CuA+CuP short, straight. Abdomen: Tergites 2–4 with setae well-developed and relatively long. Sternite 5 without projecting pregenitalic process, with desclerotized region medially. Sternite 8 subquadrate with setae longer along posterolateral margins. Hypopygium ( Figs 72View FIGURES 72 – 75, 93– 94View FIGURES 80 – 94, 105–106View FIGURES 103 – 110, 122View FIGURES 121 – 126): Large. Left epandrial lamella with ventral portion elongate (about 2X longer than high); ventral epandrial process narrowly bifurcate, dorsal arm with apex expanded, blunt or hook-like, ventral arm thick and long with minute apicodorsal seta and minute distiventral seta, apex with expanded lamelliform concavity. Dorsal lobe of left surstylus with basiventral edge rounded and flap-like, apex narrow and digitiform, with long basidorsal seta (sometimes on bump-like protuberance or tubercle), short lateral seta and long apical seta, medial surface with stalk-like projection bearing lamelliform apical seta. Ventral lobe of left surstylus shallowly bilobate in lateral view, dorsal lobe short with apex subquadrate or broadly rounded, ventral lobe broadly rounded with short marginal seta (sometimes on short tubercle) and complex upturned bifurcate projection arising medioventrally. Right epandrial lamella with ventral epandrial process not developed; basal portion of epandrial lamella narrowed and dorsally curved, with deep dorsal emargination bordering ventral margin of right cercus. Dorsal lobe of right surstylus with 3 lateral setae of similar size, apex narrowed with rounded to subtriangular tip bearing thick apicallyfrayed prensiseta on medial surface. Ventral lobe of right surstylus with lateral seta near basal third, distal 2/3 recurved, slender with narrow apically pointed lamelliform process proximal to lamelliform apex. Hypandrium large, reniform and bare. Left postgonite lobe ovoid basally, constricted near middle, distal portion subquadrate to subrectangular and flat without claw-like apicodorsal process, base of lobe with curved medial projection. Right postgonite lobe with broad lateral protuberance present or indistinct and continuous with apex, with rounded medial projection, apex bifurcate with well-developed digitiform ventral process and lamellate dorsal process. Phallus elongate with prominently projecting narrow curve and pointed dentiform process at 3/4 length. Ejaculatory apodeme subrectangular to subtriangular. Hypoproct projected dorsally as pair of slender pointed lobes, each lobe with 1–2 ventral seta proximal to apex, left lobe also with piliferous region ventrally. Cerci with anal setae well-developed and differentiated from surrounding hairs; right cercus much larger than left cercus with basal portion distended and rounded laterally, apex weakly dorsally deflected, pointed with narrow apicomedial projection, with 2 marginal setae; left cercus oblong in dorsal view, apex truncate, not dorsally deflected, with pair of thickened setae at apicolateral margin, outermost seta sometimes on short tubercle.

Female: Body length 1.9–2.5 mm, wing length 1.7–2.1 mm. Similar to male except as follows: Head: Eyes with ommatrichia of nearly uniform length, not distinctly longer on lower third. Face wider, at middle about 4.0X width of anterior ocellus. Abdomen: Tergite 5 broadly subtriangular to semicircular in dorsal view with posterior margin rounded (cf. Fig. 131View FIGURES 127 – 132). Terminalia distinctly narrower than base of segment 5 (cf. Figs 131–132View FIGURES 127 – 132); sternite 8 trough-like, with distinct basal bulge, not narrowed apically, apical half with longitudinal ridges, apex truncate (cf. Fig. 140View FIGURES 133 – 141); sternite 9 unsclerotized and indistinct; tergite 10 with hemitergites subtriangular and short, each with 2 acanthophorite spines; cercus short, pointed apically.

Distribution and seasonal occurrence. Parathalassius wheeleri  is currently known to occur on sandy seashores from Haida Gwaii and Vancouver Island in British Columbia, south along the Washington, Oregon and northern California coast to the dunes of the Samoa Peninsula, Humboldt County ( Fig. 153View FIGURES 152 – 153). Adults have been collected from mid May to mid August.

Etymology. This species is named in honour of fellow dipterist, Dr. Terry A. Wheeler, who collected a significant northern specimen of this species, plus other Parathalassius  , from Haida Gwaii, British Columbia.

Remarks. COI barcode sequences ( Fig. 154View FIGURE 154) and morphology confirm separation of P. wheeleri  from the similar allopatric P. aldrichi  (with minimally 8.2% genetic divergence). In addition, barcode sequence data obtained from specimens of P. wheeleri  indicate a significant degree of genetic divergence (averaging 2.0%) between populations from Washington, Oregon and northern California, suggesting considerable isolation of populations of this species throughout its geographic range (British Columbia populations not sequenced).

One male specimen of P. wheeleri  collected at Lanphere-Christensen Dunes in Humboldt County, California by M.E. Buegler and E.I. Schlinger, was pinned with an aphid mounted below it, suggesting that the fly was taken with an aphid prey.


Canadian National Collection of Insects, Arachnids, and Nematodes


University of British Columbia, Spencer Museum


Essig Museum of Entomology


Smithsonian Institution, National Museum of Natural History


California Academy of Sciences


California State Collection of Arthropods


Natural History Museum of Los Angeles County


University of Coimbra Botany Department