Neothalassius villosus, Brooks, Scott E. & Cumming, Jeffrey M., 2016

Brooks, Scott E. & Cumming, Jeffrey M., 2016, Neothalassius, a new genus of Parathalassiinae (Diptera: Dolichopodidae s. lat.) from the Pacific coast of South America, Zootaxa 4066 (3), pp. 311-322 : 318-320

Neothalassius villosus sp. nov.

( Figs 5–8 , 11, 12 , 19–21 , 23 )

Type material. HOLOTYPE ♂ labelled: “ CHILE: Aconcagua,/ Algarrobo, rocky coast, 23/ Nov 2006, S.A. Marshall,/ debu00283188”; “ HOLOTYPE / Neothalassius villosus / Brooks & Cumming” [red label] ( MNHNS). PARATYPE: CHILE: Tarapacá, Cuya [ca. 19°11'S 71°17'W], 26.ix.1957, on sea rocks, G. Kuschel (1♂, USNM).

Diagnosis. Males of N. villosus sp. nov. are easily distinguished from those of N. triton sp. nov. by the characters listed in the key above. Additional diagnostic features include the following: antennal postpedicel gradually tapered and narrowed in distal half ( Fig. 12 ); mid femur not swollen basally, with sparse ventral setae; mid tarsomere 1 slightly swollen in basal third with dense setulae below swelling; hind tarsus with short setae, tarsomere 1 not swollen; hypopygium ( Fig. 20 ) with right ventral epandrial process bearing pointed basal projection, apical portion claw-like, directed posteriorly with pointed apex; hypandrium elongate-reniform in lateral view; proctiger (cerci + hypoproct) strongly asymmetrical, right lobe of hypoproct much larger than left lobe ( Fig. 21 ).

Description. Male: Body length 2.0 mm, wing length 1.8–1.9 mm. Body ( Figs 5, 6 ) mainly dark grey in ground colour with greyish pruinosity, with faint bluish-green and bronze metallic tinges visible at certain angles; legs with pruinosity slightly less dense, mainly dark grey; major bristles of head (i.e., fronto-orbitals, anterior ocellars, postocellars, verticals) and thorax (i.e., dorsocentrals, supra-alars, notopleurals, post-alars, scutellars) black, other smaller setae pale unless otherwise noted. Head ( Figs 11, 12 ): Rounded in lateral view ( Figs 5 , 12 ) shorter than broad in anterior view ( Fig. 11 ), mainly grey with compound eye dull red. Occiput flat on upper median part above occipital foramen, with dark brown pruinosity. Frons about 1.5X broader than high. Face (including parafacial plates) narrower than distance between posterior ocelli, moderately protruding in lateral view. Face and parafacial plates grey. Clypeus grey. Gena moderately produced. Postgena broad in lateral view bearing short setae on upper part and long setae below. Antenna ( Fig. 12 ) entirely dark brown; postpedicel rounded in basal half, gradually tapered and narrowed in distal half; arista-like stylus shorter than postpedicel. Mouthparts with proboscis (including labrum and hypopharynx) apparently straight ( Fig. 12 ); palpus largely concealed, grey, clothed with fine setae. Thorax: Dark grey, with faint bluish-green and bronze metallic tinges visible at certain angles; scutum with dark brown pruinosity on anterior half ( Fig. 6 ); 3 dorsocentral bristles and 1 presutural supraalar bristle present, per side. Halter pale brownish. Wing: Veins brown. R1 reaching costa near middle of wing, almost in line with termination point of M4. Legs: Foreleg: Coxa with short black spine-like setae on entire anterior surface ( Fig. 5 ), trochanter and base of femur with similar spine-like setae; femur slightly longer than tibia; tarsus subequal in length to tibia; tarsomere 1 slightly shorter than combined length of tarsomeres 2–5, with large basiventral swelling, medial surface with dense field of black spine-like setae; tarsomere 2 weakly sclerotized on lateral surface; tarsomeres 2–4 decreasing slightly in length apically; tarsomere 5 subequal in length to tarsomere 2. Midleg: Femur subequal in length to tibia, not swollen basally, with sparse ventral setae; tarsus slightly shorter than tibia; tarsomere 1 slightly shorter than combined length of tarsomeres 2–5, slightly swollen in basal third with dense setulae below swelling; tarsomeres 2–4 decreasing slightly in length apically; tarsomere 5 subequal in length to tarsomere 2. Hindleg: Femur slightly longer than tibia; tibia with short setae; tarsus shorter than tibia, with short setae; tarsomere 1 not swollen, slightly shorter than combined length of tarsomeres 2–4; tarsomeres 2–4 decreasing slightly in length apically; tarsomere 5 slightly longer than tarsomere 2. Abdomen: Dark grey to greyish-brown. Sternite 1 with long, spine-like process on anterior margin projecting anteriorly between hind coxae ( Fig. 7 ). Sternite 8 enlarged and cleft along posterior margin, bearing eyelash-like row of long black setae on each side of cleft ( Fig. 8 ). Hypopygium ( Figs 19–21 ): Longer than high in lateral view. Left ventral epandrial process with 2 weak ventral setae near base ( Fig. 19 ). Right ventral epandrial process with pointed basal projection, apical portion claw-like, directed posteriorly with pointed apex projecting and visible in lateral view ( Fig. 20 ). Ventral lobe of right surstylus with ventral portion broad ( Fig. 20 ). Hypandrium elongate-reniform in lateral view. Phallus not ribbed along dorsal surface, apex bifurcate. Hypoproct ( Fig. 21 ) with right lobe larger than left lobe, left lobe lacking ventrolateral process. Cercus ( Fig. 21 ) with lateral tubercle short, right and left cercus distinctly asymmetrical. Female: Unknown.

Etymology. The specific epithet is derived from the Latin villus, meaning hairy, in reference to the distinctive pair of eyelash-like rows of elongate setae on sternite 8 of the male terminalia ( Figs 6, 8 ).

Distribution. Neothalassius villosus sp. nov. is currently known to occur on rocky seashores along the Chilean coast from Cuya in the northern Tarapacá Region (Region I), south to Algarrobo in the Valparasio Region (Region V) ( Fig. 23 ).

Figures

FIGURES 5 – 8. Neothalassius villosus sp. nov., male habitus and abdomen. 5. Lateral habitus of holotype ♂ (antennal aristalike stylus broken off). 6. Dorsal habitus of holotype ♂ (antennal arista-like stylus broken off). 7. Male abdominal sternites of paratype ♂. 8. Postabdomen of holotype ♂, dorsal view. Abbreviations: proc—process; st—sternite; tg—tergite.

FIGURES 9 – 12. Heads of males. 9. Neothalassius triton sp. nov., anterior view. 10. Neothalassius triton sp. nov., lateral view. 11. Neothalassius villosus sp. nov., anterior view. 12. Neothalassius villosus sp. nov., lateral view. Abbreviations: ar stylarista-like stylus; gn—gena; lbl—labellum; pafc—parafacial; plp—palpus; pped—postpedicel.

FIGURES 19 – 21. Neothalassius villosus sp. nov., male terminalia. 19. Hypopygium, left lateral view. 20. Hypopygium, right lateral view. 21. Proctiger, dorsal view. Abbreviations: cerc—cercus; d sur—dorsal lobe of surstylus; ej apod—ejaculatory apodeme; epand—epandrium; hypd—hypandrium; hyprct—hypoproct; pgt—postgonite; pgt lb—postgonite lobe; ph—phallus; prens—prensiseta; v epand proc—ventral epandrial process; v sur—ventral lobe of surstylus.

FIGURES 22 – 23. Distribution of Neothalassius gen. nov. 22. Known distribution of Neothalassius triton sp. nov. 22. Known distribution of Neothalassius villosus sp. nov.