Parathalassius candidatus Melander,

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: 20-22

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Parathalassius candidatus Melander


Parathalassius candidatus Melander 

( Figs 26View FIGURES 23 – 28, 40View FIGURES 38 – 47, 50, 53View FIGURES 50 – 55, 58View FIGURES 56 – 67, 81View FIGURES 80 – 94, 116View FIGURES 115 – 120, 135View FIGURES 133 – 141, 144View FIGURES 142 – 144)

Parathalassius candidatus Melander, 1906: 375  .

Type material examined. HOLOTYPE, ♀, from Friday Harbor [ca. 48°32′15″N 123° 1′10.97″W], San Juan Island, San Juan County, Washington, USA, labelled: “Friday Harbor, Wash. [summer, 1905, J.M. Aldrich]”; “TYPE/ Parathalassius  / candidatus  / Mel. [red label]”; “ALMelander/ Collection/ 1961” (USNM).GoogleMaps 

Other material examined. CANADA: British Columbia: Haida Gwaii, Graham Island , 3km N Tlell [ca. 53°33′37″N 131°55′39″W], 13.vii.1988, meadow behind dunes, T.A. Wheeler, CNC DIPTERA  #103909 (1♂, barcoded, CNC)GoogleMaps  ; Vancouver, Point Grey [ca. 49°15′58″N 123°15′52″W], 31.v.1973, on tidal flat, J.R. Vockeroth (2♂, 1♀, CNC)GoogleMaps  ; same data except, 5.vii.1973 (1♂, 5♀, CNC)GoogleMaps  ; same data except, 12.vii.1973 (12♂, 7♀, CNC)GoogleMaps  ; same data except, 19.vii.1973 (1♀, CNC)GoogleMaps  ; same data except, 23.vii.1973 (1♂, 1♀, CNC)GoogleMaps  ; same data except, 31.vii.1973 (1♀, CNC)GoogleMaps  ; Vancouver , 2.vii.1988, J.R. Vockeroth (2♂, ZFMK)  ; Vancouver, beach SW of University, lower course of Fraser River north arm, 10.vii.1988, gravel and sand, H. Ulrich (12♂, 20♀, ZFMK)  ; Vancouver Island: Deep Bay nr. Bowser [ca. 49°27′33″N 124°43′59″W],, R. Coyles (2♂, 1♀, CNC)GoogleMaps  ; Sidney Is., Sidney Spit , 48°38′28.06″N 123°19′50.05″W, 8.viii.2008, sandy beach, J.M. Cumming (1♂, 2♀, CNC)GoogleMaps  ; same data except, CNC DIPTERA  #103910 (1♀, barcode-associated, CNC)GoogleMaps  ; Cordova Bay [ca. 48°31′12″N 123°21′60″W], 11.vii.1924, A.L. Melander (1♀, USNM)  ; same data except, 11.vii.1925 (1♂, USNM; 1♀, CUIC)  . USA: California: Del Norte County: Smith River [ca. 41°55′03″N 124°12′17″W], 25.vii.1932, dry beach sand, J.M. Aldrich (3♂, USMN)GoogleMaps  ; Smith River, Tolowa Dunes State Park ,, M.E. Buegler (1♀, EMEC)  ; Smith River Dunes, (2♂, EMEC)  ; 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 [ca. 40°59′40″N 124°06′58″W], 15.v.1978, D.D. Wilder (9♂, 7♀, CAS)GoogleMaps  ; same data except, 16.v.1978 (2♂, 1♀, CAS)GoogleMaps  ; Loleta, W, sand dunes at end of Table Bluff Rd. [ca. 40°41′50″N 124°16′34″W], 28.v.2003, R. Wielgus (1♀, EMEC)GoogleMaps  ; Samoa Peninsula, Samoa Dunes Recreation Area , 40°45′41″N 124°13′37″W, 21.v.2009, J.M. Cumming (1♀, CNC)GoogleMaps  ; same data except, S.E. Brooks, CNC DIPTERA  # 103912 (1♂, barcoded, CNC)GoogleMaps  ; Samoa Beach & dunes,, J.C. Bradley (1♀, CUIC)  ; Marin County: Abbott’s Lagoon [ca. 38°07′11″N 122°57′08″W], A37,, W.H. Lenarz (1♀, EMEC)GoogleMaps  ; Dillon Beach , 38°14′57″N 122°58′00″W, 26.iii.2017, swept sandy seacoast & beach vegetation, S.E. Brooks (1♂, CNC)GoogleMaps  ; same data except, J.M. Cumming (3♀, CNC)GoogleMaps  ; same data except, S.H. Cumming (1♂, CNC)GoogleMaps  ; Muir Beach [ca. 37°51′34″N 122°34′43″W], 30.v.1946, E.L. Kessel (1♂, 1♀, EMEC)GoogleMaps  ; Stinson Beach , 37°53′51″N 122°38′28″W, 27.iii.2017, swept sandy seacoast & beach vegetation, S.E. Brooks (1♂, CNC)GoogleMaps  ; same data except J.M.Cumming (2♂, CNC)GoogleMaps  ; Mendocino County: Manchester Dunes [ca. 38°57′19″N 123°43′52″W], (5♂, 4♀, EMEC)GoogleMaps  ; San Francisco County: San Francisco [ca. 37°45′37″N 122°30′38″W], 1.vii.1952, C.E. Kaufeldt (1♂, USNM)GoogleMaps  ; same data except,, A.L. Melander (2♂, USNM)GoogleMaps  ; same data except 12.v.1915, M.C. Van Duzee (1♀, MCZ)GoogleMaps  ; same data except, 22.v.1915 (1♂, CAS)GoogleMaps  ; same data except, Sand Dunes , 13.v.1927, C.L. Fox (1♀, EMEC)GoogleMaps  ; Sonoma County: Bodega Dunes [ca. 38°20′16″N 123°04′02″W], (1♀, EMEC)GoogleMaps  ; Salmon Creek, North Salmon Creek State Beach , 38°21′21″N 123°03′59″W, 24.iii.2017, swept sandy seacoast & beach vegetation, S.E. Brooks (1♂, CNC)GoogleMaps  ; same data except, 25.iii.2017 (1♂, CNC)GoogleMaps  . Oregon: Coos County: Bandon, Bullards Beach, 43°08′44″N 124°24′56″W, 29.v.2009, swept beach-grass, S.E. Brooks (2♂, 1♀, CNC)GoogleMaps  ; same data except, J.M. Cumming (1♀, CNC)GoogleMaps  ; Curry County: Winchuck River , [ca. 42°00′17″N 124°12′54″W], 23.vii.1932, J.M. Aldrich (2♂, 1♀, USNM)GoogleMaps  ; 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, CNC487110View Materials (1♀, barcode-associated, CNC)GoogleMaps  ; Suislaw North Jetty, nr. Florence , 44°01′07.0″N 124°08′12.6″W, 8.vii.2014, swept dunes & beach grass ( Ammophila  ), S.E. Brooks (3♂, 2♀, CNC)GoogleMaps  ; same data except, J.M. Cumming (1♂, 1♀, CNC)GoogleMaps  ; same data except, CNC588238View Materials (1♂, barcoded, CNC), CNC588237View Materials (1♀, barcode-associated, 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  ), S.E. Brooks (3♂, 1♀, CNC)GoogleMaps  ; same data except, CNC588235View Materials (1♂, barcoded, CNC), CNC588236View Materials (1♀, barcode-associated, CNC)GoogleMaps  . Washington: Clallam County: Twin [ca. 48°09′54″N 123°56′58″W],, sandy beach, H. Ulrich (1♀, ZFMK)GoogleMaps  ; Pacific County: 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 (2♂, 2♀, CNC; 1♂, 1♀, CSCA)GoogleMaps  ; same data except, CNC487204View Materials (1♀, barcode-associated, CNC)GoogleMaps  ; same data except, J.M. Cumming (1♂, 5♀, CNC)GoogleMaps  ; same data except, CNC487203View Materials (1♂, barcoded, CNC)GoogleMaps  ; same data except, 2.vii.2014, S.E. Brooks (3♀, CNC)GoogleMaps  ; same data except, 2.vii.2014, J.M. Cumming (5♂, 1♀, CNC)GoogleMaps  ; same data except, 1. vii.2 0 14, swept dunes & beach vegetation, S.H. Cumming (3♀, CNC)GoogleMaps  ; same data except, 2.vii.2014, (1♀, CNC)GoogleMaps  ; Ilwaco, Cape Disappointment , 23.vii.1993, H. Ulrich (14♂, 8♀, ZFMK)GoogleMaps  ; same data except, 24.vii.1993 (21♂, 20♀, ZFMK)GoogleMaps  ; same data except, 25.vii.1993 (15♂, 23♀, ZFMK)GoogleMaps  ; same data except, 26.vii.1993 (62♂, 1♀, ZFMK)GoogleMaps  ; same data except, Benson Beach , 24.vii.1993, dunes (1♂, ZFMK)GoogleMaps  ; same data except, 5.viii.1994 (9♂, 12♀, ZFMK)GoogleMaps  ; same data except, 9.viii.1994 (9♂, 2♀, ZFMK)GoogleMaps  ; same data except, 27.vii.1993, on wet sand (5♂, 6♀, ZFMK)GoogleMaps  ; same data except, 5.viii.1994, sandy beach (27♂, 2♀, ZFMK)GoogleMaps  ; same data except, 8.viii.1994 (32♂, 3♀, ZFMK)GoogleMaps  ; same data except, 10.viii.1994 (15♂, ZFMK)GoogleMaps  ; same data except, Waikiki Beach , 15.vii.1988, on sand (22♂, 8♀, ZFMK)GoogleMaps  ; same data except, 17.vii.1988, on rock (1♀, ZFMK)GoogleMaps  ; same data except, 22.vii.1993, dunes (1♂, ZFMK)GoogleMaps  ; same data except, 26.vii.1993, on wet sand (19♀, ZFMK)GoogleMaps  ; same data except, 22.vii.1993, sandy beach (3♂, 3♀, ZFMK)GoogleMaps  ; same data except, 9.viii.1994 (30♂, 2♀, ZFMK)GoogleMaps  ; Ilwaco [ca. 46°16′20″N 124°04′25″W], vii.1917, A.L. Melander (2♂, 2♀, USNM)GoogleMaps  ; San Juan County: San Juan Island, Kanaka Bay [ca. 48°29′03″N 123°05′4″W], 8.vii.1924, A.L. Melander (1♂, USNM)GoogleMaps  .

Diagnosis. This relatively large species is characterized by 3–4 notopleural bristles, dark legs, relatively long vein CuA+CuP, males with greyish-white pruinosity on the face and clypeus, and longer lower male ommatrichia. Parathalassius candidatus  is very similar to P. abela  , but males of the former species can be distinguished by a face and clypeus that is concolourous with the greyish-white frons. Females of these two species are virtually identical. Parathalassius candidatus  is also similar to P. sinclairi  sp. nov. and P. susanae  sp. nov., but all three species can be differentiated by the structure of the hindleg and female sternite 8, as indicated in the key

Redescription. Male: Body length 3.0– 3.9 mm, wing length 3.0– 3.5 mm. Dark brown ground colour covered mostly with dense greyish-white pruinosity. Setae of body and legs white. Head ( Fig. 26View 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 2.0X width of anterior ocellus. Gena and postgena with moderately long white setae, forming short beard flanking mouthparts. Antenna ( Fig. 40View FIGURES 38 – 47) including arista-like stylus, entirely dark brown; postpedicel subtriangular, 1.5–1.7X longer than wide; arista-like stylus long, about 2.0X length of postpedicel. Palpus with 2–3 moderately long setae and several short setulae on outer surface of apical half. Thorax: Acrostichal setulae quadriserial; 6–8 dorsocentral bristles, 0– 1 presutural intra-alar bristles, 1–2 presutural supra-alar (posthumeral) bristles, 2–3 postsutural supra-alar bristles, 3–4 notopleural bristles. Scutellum with 3 pairs of bristles. Legs: Foreleg: Dark grey, pale only at knee. Coxa with moderately long pale setae on anterior surface. Femur with numerous long setae on posterior surface, posterodorsal and posteroventral rows prominent. Tibia with short setae and setulae. Tarsus with setulae; tarsomeres 1–2 not dilated. Midleg: Dark grey, pale only at knee, tarsus greyish-brown. Femur with anteroventral and posteroventral row of setae prominent. Tibia with pair of apicoventral bristles. Tarsomeres 1–4 each with pair of dark spine-like apicoventral setae. Hindleg ( Figs 50, 53View FIGURES 50 – 55): Dark grey, femur dark brown posteriorly, tarsus greyish-brown. Femur with ventral row of setae prominent. Tibia with anterodorsal and anteroventral rows of setae prominent, mostly longer than width of tibia, with anterodorsal row of setae evenly curved towards apex of tibia. Tarsus slightly shorter than tibia with short setae and setulae; tarsomere 1 slightly shorter than combined length of tarsomeres 2–4; tarsomeres 1–3 with several short thickened angled setae dorsally, not perpendicular and peg-like; tarsomere 2 distinctly longer than tarsomere 3; tarsomere 3 slightly longer than tarsomere 4; tarsomere 5 subequal in length to tarsomere 3. Wing ( Fig. 58View FIGURES 56 – 67): Hyaline with dark brown veins. Cell dm produced apically, dm-m crossvein concave. Vein CuA+CuP relatively long, slightly curved to straight. Abdomen: Tergites 2–4 with setae well-developed and relatively long. Sternite 5 with slender anteriorly curved digitiform pregenitalic process present, base with short blunt anterior projection, apex blunt and covered with microtrichia, posterior edge of sternite 5 (behind process) deeply emarginate. Sternite 8 subquadrate with prominent elongate setae on posterolateral margins. Hypopygium (virtually indistinguishable from that of P. abela  sp. nov.) ( Figs 81View FIGURES 80 – 94, 116View FIGURES 115 – 120): Large. Left epandrial lamella with ventral portion elongate (about 2X longer than high); ventral epandrial process broadly bifurcate, dorsal arm curved ventrally, narrow in middle portion, apex expanded and hook-like, ventral arm thick with minute apicodorsal seta and pair of minute setae along distiventral margin, apex with expanded lamelliform concavity. Dorsal lobe of left surstylus subtriangular with basiventral edge weakly rounded, with long basidorsal seta, short lateral seta and long apical seta, medial surface with knob-like projection bearing lamelliform apical process. Ventral lobe of left surstylus shallowly bilobate in lateral view, dorsal lobe short with apex subquadrate, ventral lobe with rounded base bearing short lateral seta and complex upturned multilobate 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 (apical-most seta somewhat stronger), apex narrowed with squared-off tip bearing thick apicallyfrayed prensiseta on medial surface. Ventral lobe of right surstylus with lateral seta near middle, distal half recurved and tapered with tubercle bearing strong seta proximal to rounded apex. Hypandrium very large, elongatereniform with convex anterior and posterior ends extending to or beyond margins of epandrial lamellae in lateral view, mainly bare except for a few short setae lateroventrally on left side, and posteriorly on right side. Left postgonite lobe subquadrate basally, constricted near middle, with distal portion broadly lamelliform with clawlike apical process, base of lobe with slender medial projection. Right postgonite lobe with broad lateral protuberance and bulbous medial projection, apex bifurcate with short digitiform process and rounded lamelliform process. Phallus (cf. Figs 95–96View FIGURES 95 – 102) short and weakly curved, broad in basal 2/3 with apical 1/3 narrower (in lateral view), dorsal flange and left lateral bump-like protuberance present at 2/3 length. Ejaculatory apodeme broadly subtriangular. Hypoproct strongly projected dorsally as pair of slender blade-like lobes. Cerci with anal setae welldeveloped and differentiated from surrounding hairs; right cercus much larger than left cercus with basal portion distended and rounded laterally, apex strongly deflected dorsally, elongate narrow and pointed with 2 short preapical setae on lateral margin; left cercus oblong-subrectangular in dorsal view, apex short and truncate, with 2 long, dorsally-directed setae.

Female: Body length 3.4–4.1 mm, wing length 3.0–4.0 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 4.0– 5.0X width of anterior ocellus. Legs: Foreleg: Coxa with shorter more slender pale setae on anterior surface. Femur with posteroventral row of setae only prominent apically. Midleg: Femur with anteroventral and posteroventral setae less prominent. Hindleg: Tarsomeres 1–3 without slightly thickened setae dorsally. 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, lacking basal bulge, widened just beyond base and narrowed apically, apical half with longitudinal ridges, apex broadly truncate ( Fig. 135View FIGURES 133 – 141); sternite 9 reduced to narrow transverse sclerotized band; tergite 10 with hemitergites subtriangular and short, each with 2 acanthophorite spines; cercus short, pointed apically.

Distribution and seasonal occurrence. Parathalassius candidatus  is currently known to occur on sandy seashores from Haida Gwaii, Vancouver Island and Vancouver, British Columbia, south along the Washington, Oregon and California coasts to San Francisco ( Fig. 144View FIGURES 142 – 144). Adults have been collected from late March to mid August.

Remarks. Although the locality label of the holotype does not indicate collection date or collector, Melander (1906) states that the specimen was collected in the summer of 1905 by J.M. Aldrich.

COI barcode sequences ( Fig. 154View FIGURE 154) and morphology confirm separation of this species from the very similar allopatric P. abela  (with minimally 3.6% genetic divergence).


Canadian National Collection of Insects, Arachnids, and Nematodes


Zoologisches Forschungsmuseum Alexander Koenig


Smithsonian Institution, National Museum of Natural History


Cornell University Insect Collection


Essig Museum of Entomology


California Academy of Sciences


Museum of Comparative Zoology


California State Collection of Arthropods


University of Coimbra Botany Department














Parathalassius candidatus Melander

Cumming, Jeffrey M. 2017

Parathalassius candidatus

Melander 1906: 375