Parathalassius dilatus, Cumming, 2017

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 : 22-24

publication ID	https://doi.org/ 10.11646/zootaxa.4314.1.1
publication LSID	lsid:zoobank.org:pub:6758Dc40-4356-4Adc-9Bd6-456652Ea5162
DOI	https://doi.org/10.5281/zenodo.6022484
persistent identifier	https://treatment.plazi.org/id/03E9879C-8D28-FFDE-57E0-2D29FDE45840
treatment provided by	Plazi
scientific name	Parathalassius dilatus
status	sp. nov.

Treatment

Parathalassius dilatus View in CoL sp. nov.

( Figs 48–49 View FIGURES 48 – 49 , 85 View FIGURES 80 – 94 , 101–102 View FIGURES 95 – 102 , 126 View FIGURES 121 – 126 , 145 View FIGURES 145 – 147 )

Type material. HOLOTYPE ♂ from Naples [ca. 33°45′07″N 118°08′00″W], Los Angeles County, California, labelled: “Naples/ Cal/ IV-7-18 ”; “C.W. Johnson/ Collection”; “ Parathalassius / n.sp. [handwritten on both sides]”; “ Parathalassius / melanderi / Cole/ det WJ Turner 1978”; “MCZ-ENT [barcode symbol] 0 0 529580 [printed on both sides]” “HOLOTYPE/ Parathalassius dilatus / Brooks & Cumming [red label]” (MCZ). PARATYPE: USA: California: Los Angeles County, El Segundo Dunes [ca. 33°55′N 118°26′W], 29.IV.1986, UCRC ENT 461755 (1♂, UCRC).

Diagnosis. This relatively small distinctive species is characterized by a male with foretarsomeres 1–2 dilated, longer lower male ommatrichia, 2 notopleural bristles, and wing that is apically infuscate.

Description. Male ( Figs 48–49 View FIGURES 48 – 49 ): Body length 2.4 mm, wing length 2.3 mm. Dark brown ground colour covered mostly with dense greyish-white pruinosity. Setae of body and legs white. Head ( Figs 48–49 View FIGURES 48 – 49 ): 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. Gena and postgena with long white setae, forming distinct beard flanking mouthparts. Antenna ( Fig. 49 View FIGURES 48 – 49 ) including aristalike stylus, dark brown; postpedicel subtriangular, 1.5X longer than wide; arista-like stylus of medium length, about 1.5X length of postpedicel. Palpus with dense brush of 10–12 setae on outer surface of apical half. Thorax: Acrostichal setulae biserial; 7 dorsocentral bristles, 0 presutural intra-alar bristles, 1 presutural supra-alar (posthumeral) bristle, 3 postsutural supra-alar bristles, 2 notopleural bristles. Scutellum with 2 pairs of bristles. Legs: Foreleg: Dark grey to brownish grey, pale at knee and apex of tibia, tarsomeres 1–2 pale yellowish-brown, tarsomeres 3–5 pale brown to dark brown (darker apically). Coxa with moderately long stout pale setae, densely covering anterior surface. Femur with moderately long setae on posterior surface. Tibia with short setae and setulae. Tarsus with setulae, tarsomeres 2–4 each with dark stout apicoventral seta (stoutest on tarsomere 2); tarsomere 1 dilated, distinctly thicker than tarsomeres 3–5 ( Figs 48–49 View FIGURES 48 – 49 ); tarsomere 2 slightly expanded. Midleg: Dark grey, pale at knee and apex of tibia, tarsomeres 1–2 pale yellowish-brown, tarsomeres 3–5 pale brown to dark brown, darker apically. Femur with anterodorsal setae most prominent, short to moderately long. Tibia with 1 apicoventral bristle. Tarsomeres 1–4 each with a few dark spine-like apicoventral setae. Hindleg: Dark grey, femur dark brown posteriorly, pale at knee and extreme apex of tibia, tarsomere 1 and base of tarsomere 2 pale yellowishbrown, apex of tarsomere 2 and tarsomeres 3–5 brown to dark brown, darker apically. Femur with anteroventral row of setae most prominent, short or absent basally, longer apically. Tibia clothed with short setae. Tarsus longer than tibia with short setae and setulae; tarsomere 1 long, but shorter than combined length of tarsomeres 2–4; tarsomeres 1–4 lacking peg-like or thickened setae dorsally; tarsomere 2 long, longer than tarsomere 3; tarsomere 3 long, longer than tarsomere 4; tarsomere 4 slightly longer than tarsomere 5. Wing (cf. Fig. 60 View FIGURES 56 – 67 ): Infuscate apically, hyaline basally, with yellowish veins basally and dark brown veins apically. Cell dm produced apically (dm-m crossvein with aberrant stub vein on holotype). Vein CuA+CuP short, straight. Abdomen: Tergites 2–4 with setae well-developed. Sternite 5 without projecting pregenitalic process, posterior edge of sternite deeply emarginate. Sternite 8 subquadrate with setae longer along posterolateral margins. Hypopygium ( Figs 85 View FIGURES 80 – 94 , 101–102 View FIGURES 95 – 102 , 126 View FIGURES 121 – 126 ): Large. Left epandrial lamella with ventral portion elongate (about 2X longer than high); ventral epandrial process broadly bifurcate, dorsal arm elongate and strongly hooked ventrally, more or less evenly slender basally with apex slightly expanded, ventral arm thick with minute apicodorsal seta and minute distiventral seta, apex with expanded lamelliform concavity. Dorsal lobe of left surstylus subtriangular, with basiventral edge broadly rounded, apex pointed, 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 rounded, ventral lobe with rounded base bearing short lateral seta and complex upturned bifurcate projection arising medioventrally. Right epandrial lamella with ventral epandrial process very short and broad; 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 (lowermost seta weaker), apex rounded bearing thick apically-frayed prensiseta on medial surface. Ventral lobe of right surstylus recurved at base with lateral seta near middle, with elongate finely-tipped process proximal to narrow apex. Hypandrium very large, elongate-reniform with convex anterior and posterior ends extending to or beyond margins of epandrial lamellae in lateral view, bare. Left postgonite lobe ovoid basally, constricted near middle, distal portion subrectangular and flat without claw-like apical process, base of lobe with broad curved apically-pointed medial projection. Right postgonite lobe with broad lateral protuberance pointed at apical margin and lamelliform medial projection, apex bifurcate with short digitiform process and rounded lamelliform process. Phallus relatively short and moderately curved, gradually tapering distally, apex straight. Ejaculatory apodeme broadly subtriangular. Hypoproct projected dorsally as pair of subtriangular lobes, each lobe with 3 preapical ventral setae, left lobe with piliferous flange lateral to lower seta. 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 deflected dorsally, truncate with pair of setae along apicolateral margin; left cercus oblong-subrectangular in dorsal view, apex even with apex of right cercus, weakly deflected dorsally, broadly truncate with pair of apical setae.

Female: Unknown.

Distribution and seasonal occurrence. Parathalassius dilatus is currently known only from two male specimens collected from El Segundo Dunes and adjacent Long Beach (Naples) in Los Angeles County in southern California (see Remarks) ( Fig. 145 View FIGURES 145 – 147 ) in April.

Etymology. The specific name refers to the expanded tarsomeres 1–2 of the male foreleg.

Remarks. The most recent specimen (paratype) of this species was collected by R. Mattoni and R. Rogers in 1986 during a survey of the El Segundo dune reserve located along the western edge of the Los Angeles International Airport. This approximately 80 hectare reserve is the largest remaining habitat in the historical coastal El Segundo dune system in southwestern Los Angeles ( Mattoni 1990). The dune system supports several rare species of insects and plants, including the endangered El Segundo blue butterfly, Euphilotes battoides allyni (Shields) , and the El Segundo giant flower-loving fly, Rhaphiomidas terminatus terminatus Cazier (Mydidae) , which was until recently thought to be extinct ( George & Mattoni 2006). The holotype of P. dilatus was collected in 1918 from Naples, likely at nearby Long Beach, which abuts the southern edge of the El Segundo dune system. Parathalassius dilatus probably represents another rare species of fly that is restricted to the El Segundo and historically adjacent dune systems.