Neothalassius triton, 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 : 315-318

Neothalassius triton sp. nov.

( Figs 3, 4 , 9, 10 , 13–18, 22)

Type material. HOLOTYPE ♂ labelled: “ CHILE: Aconcagua,/ Algarrobo, rocky coast, 23/ Nov 2006, S.A. Marshall,/ debu00283164”; “ HOLOTYPE / Neothalassius triton / Brooks & Cumming” [red label] ( MNHNS). PARATYPES: CHILE: same data as holotype [ca. 33°22'S 71°42'W] except, debu00283172, debu00283177, debu00283190, debu00283180 (3♂, 1♀, respectively, DEBU); same data as holotype except, debu00283174, debu00283170 (1♂, 1♀, respectively, CNC); Valparasio Region, Cachagua, shoreline, rocks 32°34.90'S 71°27.40'S 8.xii.2008, Kits & Marshall (1♂, DEBU); Coquimbo Region, Punta Teatinos [ca. 29°49'S 71°17'W], 16.ix.1952, G. Kuschel (2♂, 1♀, USNM); same data except 13.x.1957, on seashore, G. Kuschel (1♀, USNM); Los Lagos Region, Chiloé Island, Chepu [ca. 42°03'S 74°02'W], x.1958, on seashore, G. Kuschel (1♂, 1♀, USNM).

Diagnosis. Males of N. triton sp. nov. are easily distinguished from those of N. villosus sp. nov. by the characters listed in the key above. Additional diagnostic features include the following: antennal postpedicel strongly tapered and narrowed in distal half ( Fig. 10 ); mid femur slightly swollen in basal third with dense setulae below swelling; mid tarsomere 1 not swollen basally, with series of hook-like setulae ventrally; hind tarsomeres 1– 4 with elongated medioapical setae, tarsomere 1 somewhat swollen with narrowed base ( Fig. 4 ); hypopygium ( Fig. 17 ) with right ventral epandrial process lacking basal projection, with apical portion directed dorsally and mostly hidden in lateral view; hypandrium reniform in lateral view; proctiger (cerci + hypoproct, Fig. 18 ) slightly asymmetrical with right and left lobes similar in shape and size.

Description. Male: Body length 1.2–1.6 mm, wing length 1.5–1.9 mm. Body ( Fig. 3 ) dark grey to greyishbrown in ground colour with greyish pruinosity, with faint bluish-green and bronze metallic tinges visible at certain angles; legs with pruinosity slightly less dense, brownish-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 9, 10 ): Ovoid in lateral view ( Fig. 10 ), higher than broad in anterior view ( Fig. 9 ), mainly dark grey with compound eye dull red. Occiput weakly concave on upper median part above occipital foramen. Frons about 2X broader than high. Face (including parafacial plates) about as broad as distance between posterior ocelli, strongly protruding in lateral view. Face and medial edge of parafacial plates brownish. Clypeus brown. Gena strongly produced. Postgena moderately broad in lateral view bearing short setae. Antenna ( Fig. 10 ) entirely dark brown; postpedicel rounded in basal half, strongly tapered and narrowed in distal half; arista-like stylus longer than postpedicel. Mouthparts with proboscis (including labrum and hypopharynx) distinctly curved ( Fig 10 ); palpus exposed and mostly visible, dark brown, clothed with fine setae. Thorax: Dark grey to greyish-brown, with faint bluish-green and bronze metallic tinges visible at certain angles especially on scutum; 4 dorsocentral bristles present and 1 presutural supra-alar bristle present or absent, per side. Halter pale brownish-white. Wing (Fig. 13): Veins brown. R1 reaching costa before middle of wing, well before termination point of M4. Legs: Foreleg: Coxa with short, black, spine-like setae on lower anterior surface only, trochanter and base of femur without similar spine-like setae; femur slightly longer than tibia; tarsus subequal in length to femur; tarsomere 1 slightly shorter than combined length of tarsomeres 2–5, with slight ventromedial excavation, medial surface apparently with sparsely distributed, indistinct black spine-like setae; tarsomeres 2–4 decreasing slightly in length apically; tarsomere 5 slightly longer than tarsomere 2. Midleg: Femur subequal in length to tibia, basal third slightly swollen with dense setulae below swelling; tarsus slightly longer than tibia; tarsomere 1 subequal to combined length of tarsomeres 2–5, with series of hook-like setulae ventrally; tarsomeres 2–4 decreasing slightly in length apically; tarsomere 5 subequal in length to tarsomere 2. Hindleg: Femur slightly longer than tibia; tibia with well-developed setae on dorsal and lateral surfaces; tarsus ( Fig. 4 ) slightly shorter than tibia; tarsomeres 1–4 with elongated medioapical setae; tarsomere 1 somewhat swollen with narrowed base, subequal to combined length of tarsomeres 2–4, tarsomeres 2–4 decreasing slightly in length apically; tarsomere 5 longer than tarsomere 2. Abdomen: Dark grey to greyish-brown. Sternite 1 with short, rounded medial process on anterior margin. Sternite 8 lacking cleft along posterior margin, sparsely covered with short unmodified setae. Hypopygium ( Figs 16–18 ): About as long as high in lateral view. Left ventral epandrial process with 2 strong ventral setae near base ( Fig. 16 ). Right ventral epandrial process lacking basal projection, apical portion directed dorsally and lying adjacent to phallus, mostly hidden in lateral view ( Fig. 17 ). Ventral lobe of right surstylus with ventral portion narrow ( Fig. 17 ). Hypandrium reniform in lateral view. Phallus with apical portion ribbed along dorsal surface, apex not bifurcate. Hypoproct ( Fig. 18 ) with right and left lobes similar in size, left lobe with narrow ventrolateral process. Cercus ( Fig. 18 ) with lateral tubercle well-developed, right and left cercus slightly asymmetrical. Female: Similar to male except as follows: foreleg with tarsomere 1 unmodified, lacking ventromedial excavation; base of mid femur not swollen and with only sparse setulae ventrally; terminalia as in description of genus (see above).

Etymology. The specific epithet is named after the Greek god Triton , the messenger of the sea, in reference to the coastal distribution of this species.

Distribution. Neothalassius triton sp. nov. is currently known to occur on rocky seashores along the Chilean coast from Punta Teatinos in the Coquimbo Region (Region IV), south to Chepu on Chiloé Island in the Los Lagos Region (Region X) ( Fig. 22 ).

FIGURES 13–15. Neothalassius triton sp. nov., wing and female terminalia. 13. Male wing. 14. Female terminalia, dorsal view. 15. Female terminalia, lateral view. Abbreviations: bm-m—basal medial crossvein; C—costal vein; cerc—cercus; CuAanterior branch of cubital vein; cua—anterior cubital cell; CuP—posterior branch of cubital vein; h—humeral crossvein; M1, M4—medial veins; R1, R2+3, R4+5—radial veins; Sc—subcostal vein; spmth—spermatheca; st—sternite; tg—tergite.

Figures

FIGURES 1 – 4. Neothalassius gen. nov., habitat photographs, male habitus and hindleg. 1 – 2. Rocky coastal site at Algarrobo, Chile, with Santiago dipterist Christian Gonzalez in foreground at left (photographs by Steve Marshall). 3. Neothalassius triton sp. nov., lateral habitus of holotype ♂. 4. Neothalassius triton sp. nov., male hindleg, apex of tibia and tarsus, dorsal view. Abbreviation: tsm—tarsomere.

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 16 – 18. Neothalassius triton sp. nov., male terminalia. 16. Hypopygium, left lateral view. 17. Hypopygium, right lateral view. 18. 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; 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.