Parathalassius aldrichi 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: 16-17

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Parathalassius aldrichi Melander


Parathalassius aldrichi Melander 

( Figs 73–75View FIGURES 72 – 75, 92View FIGURES 80 – 94, 103–104View FIGURES 103 – 110, 121View FIGURES 121 – 126, 140View FIGURES 133 – 141, 143View FIGURES 142 – 144)

Parathalassius aldrichi Melander, 1906: 374  .

Type material examined. LECTOTYPE (here designated in order to fix identity of the species), ♂, from Pacific Grove [ca. 36°37′08″N 121°54′9″W], Monterey County, California, USA, labelled: “Pacific Grove/ v.7. [19]06 Cal. [J.M. Aldrich]”; “COTYPE/ Parathalassius Aldrichii  [sic.]/ ♂ Mel.”; “LECTOTYPE/ Parathalassius  / aldrichi Melander  / des. Brooks & Cumming 2016 [red label]” (USNM). PARALECTOTYPES: USA: California: same locality and date as lectotype (8♂, 7♀, USNM; 1♂, 1♀, AMNH). Our paralectotype label has additionally been attached to each specimen.

Other material examined. USA: California: Marin County: Abbott’s Lagoon [ca. 38°07′11″N 122°57′08″W],, W.H. Lenarz (1♀, EMEC)GoogleMaps  ; Point Reyes National Seashore, North Beach [ca. 38°06′23″N 122°57′45″W], el. <100 ft, 13.v.1972, D.E. Schultz (1♂, EMEC)GoogleMaps  ; Point Reyes, North Beach , 13.v.1978, M.E. Beugler (1♀, EMEC)  ; Stinson Beach , 37°53′51″N 122°38′28″W, 27.iii.2017, swept sandy seacoast & beach vegetation, S.E. Brooks (9♂, 10♀, CNC)GoogleMaps  ; same data except, J.M. Cumming (7♂, 6♀, CNC)GoogleMaps  ; same data except, S.H. Cumming (2♂, CNC)GoogleMaps  ; Mendocino County: Inglenook Fen, 4 mi. N. Ft. Bragg [ca. 39°30′55″N 123°46′38″W], 7.v.1975, M.E. Buegler (1♂, EMEC)GoogleMaps  ; same data except, 26.v.1975 (1♀, EMEC)GoogleMaps  ; same data except,, M.E. Buegler & E.I. Schlinger (1♂, 3♀, EMEC)GoogleMaps  ; same data except, (1♀, EMEC)GoogleMaps  ; same data except, 17.vii.1975 (2♂, 2♀, EMEC)GoogleMaps  ; same data except,, E.I. Schlinger (1♀, EMEC)GoogleMaps  ; same data except, dune area, (2♂, 2♀, EMEC)GoogleMaps  ; Monterey County: Asliomar [ca. 36°36′60″N 121°56′19″], 17.v.1959, D.J. Burdick (4♂, 1♀, EMEC)  ; San Francisco County: San Francisco, beach west end Judah St. , 37°45′37″N 122°30′38″W, swept beach vegetation, 8.viii.1999, S.E. Brooks (6♂, 8♀, LEM)GoogleMaps  ; same data except, CNC DIPTERA  #’s 103906, 103907 (2♂, barcoded, LEMQ)GoogleMaps  ; San Luis Obispo County: Morro Bay, dunes nr. Morro Rock , 35°22′16.4″N 120°51′52.0″W,, swept sandy seacoast & beach vegetation, S.E. Brooks (82♂, 43♀, CNC; 2♂, 2♀, CSCA)GoogleMaps  ; same data except, CNC573170View Materials, CNC573167View Materials (2♂, barcoded, CNC), CNC573158View Materials, CNC573157View Materials (2♀, barcode-associated, CNC)GoogleMaps  ; same data except, J.M. Cumming (9♂, 7♀, CNC)GoogleMaps  ; same data except, CNC580872View Materials, CNC580869View Materials (2♂, barcoded, CNC), CNC580879View Materials, CNC580886View Materials (2♀, barcodeassociated, CNC)GoogleMaps  ; Morro Bay , 26.ix.1946, A.L. Melander (1♀, USNM)  ; same data except,, (7♂, 1♀, USNM)  ; Morro Dunes , 6.ix.1945, A.L. Melander (1♀, USNM)  ; same data except, (3♂, 2♀, USNM)  ; San Mateo County: Half Moon Bay [ca. 37°27′36″N 122°26′41″W], dunes, 11.v.1981 (14♂, 8♂, EMEC)GoogleMaps  ; Santa Cruz County: Ano Nuevo dunes [ca. 37°06′60″N 122°18′21″W], 8.v.1981 (19♂, 12♀, EMEC)  .

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

Redescription. Male: Body length 1.6–2.2 mm, wing length 1.5–1.9 mm. Dark brown ground colour covered mostly with dense greyish-white pruinosity. Setae of body and legs white. Head (cf. 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 (cf. 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 (cf. 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 73–75View FIGURES 72 – 75, 92View FIGURES 80 – 94, 103–104View FIGURES 103 – 110, 121View 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 hooklike, 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 broadly rounded, 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 apically-frayed 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 near apex. Ejaculatory apodeme subrectangular to subtriangular. Hypoproct projected dorsally as pair of slender pointed lobes, each lobe with 1–2 ventral setae 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, truncate with apicomedial margin blunt, 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 1.9–2.8 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 ( 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 aldrichi  is currently known to occur on sandy seashores along the California coast from Fort Bragg in Mendocino County south to the dunes of Morro Bay in San Luis Obispo County ( Fig. 143View FIGURES 142 – 144). Adults have been collected from late March to late September.

Remarks. Some paralectotypes bear separate labels reading “JMAldrich/ Coll” and “sand dune(s)”. Melander (1906) also indicates that the type series of P. aldrichi  was collected by J.M. Aldrich on “dry sands in back of the beach”. We also collected numerous specimens of P. aldrichi  by sweeping vegetation along the back dune area of Morro Bay ( Fig. 17View FIGURES 17 – 22).

COI barcode sequences ( Fig. 154View FIGURE 154) and morphology confirms the separation of this species from the similar allopatric P. wheeleri  sp. nov. (with minimally 8.2% genetic divergence). However within P. aldrichi  , the San Francisco population shows significant genetic divergence (with minimally 6.2% divergence) from the Morro Bay population, suggesting the possibility of another cryptic species in this complex. All the populations of P. aldrichi  , including the type locality population from Pacific Grove, appear morphologically identical. Because the unsequenced Pacific Grove type locality population is located midway between the two sequenced populations, it seemed prudent to treat all populations together as P. aldrichi  , until additional sampling and sequencing is completed.


Essig Museum of Entomology


Canadian National Collection of Insects, Arachnids, and Nematodes


McGill University, Lyman Entomological Museum


California State Collection of Arthropods


Smithsonian Institution, National Museum of Natural History


University of Coimbra Botany Department














Parathalassius aldrichi Melander

Cumming, Jeffrey M. 2017

Parathalassius aldrichi

Melander 1906: 374