Chimerothalassius riparius Brooks & Cumming 2022, sp. nov.
Creators: name: Brooks, Scott E.
name: Cumming, Jeffrey M.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Dolichopodidae
Chimerothalassius
Chimerothalassius riparius

description: Chimerothalassius riparius sp. nov.
(Figs 8–10, 19–25)
urn:lsid:zoobank.org:act: CD5E6F66-2F72-4B6B-8235-30B3DDBE6D23
Type material. HOLOTYPE ♂ labelled: “ NEW CALEDONIA: Parc/ Rivève[sic] Bleue; R.Bleue/ nr. Refuge [ca 22°05ʹ50ʺS 166°38ʹ17ʺE], 20–21.vii./ 1995; B.J. Sinclair / ex. yellow pans”; “ CNC/ 1155797 ”; “ HOLOTYPE / Chimerothalassius riparius / Brooks & Cumming [red label]” (MNHN). PARATYPES: NEW CALEDONIA: same data as holotype (1♀, CNC); same data as holotype except, CNC1155799 (1♀, MNHN).
Diagnosis. Chimerothalassius riparius sp. nov. is distinguished from the other known Australasian species of the genus by its brown, capitate palpus (Fig. 19). Males are further distinguished by several hypopygial features (Figs 23–25) including: left ventral epandrial process with tip weakly bent; left ventral surstylus long and narrow with short setae; right ventral epandrial process strongly upcurved; phallus with tip not expanded and lacking process near midlength; hypoproct bifid with narrow dorsal lobe and longer broader ventral lobe. Females are further characterized by their terminalia with acanthophorous spines and pointed, upturned cercus (Fig. 21).
Description. Male (Figs 19, 20, 22–25): Wing length 1.10 mm. Head (Figs 19, 20): Dark grey pruinose with green and bronze reflections dorsally; broader than thorax in dorsal view; ovoid in lateral view (higher than broad); about as broad as high in anterior view; larger setae black. Ocellar triangle conspicuous. Occiput concave on upper median part. Eyes covered with short ommatrichia; medial edge of eye with distinct emargination adjacent to antenna; ommatidia progressively smaller anterodorsally. Frons 2.3X broader than high, widening above. Face narrow, with eyes nearly contiguous, concolorous with rest of head. Clypeus not separated from face, small and triangular, weakly produced medially, brownish medially, grey laterally. Setae of head well differentiated: 1 pair of weakly inclinate fronto-orbitals about midway between base of antennae and ocellar triangle; 1 pair of lateroclinate anterior ocellars; 1 pair of small posterior ocellars; 1 pair of weakly inclinate inner verticals (sometimes referred to as postocellars); 2 pairs of lateroclinate outer verticals; postoculars short fine and pale, upper setae uniserial, lower setae scattered, lowermost seta longer. Antenna entirely dark brown, inserted slightly above middle of head in profile; scape short, funnel-shaped; pedicel subequal in length to scape, spheroidal with subapical circlet of setulae; postpedicel 1.1X longer than wide, bulb-shaped with very short narrow tip, clothed in fine setulae; arista-like stylus 3X length of postpedicel, with minute hairs. Palpus brown, narrow basally, abruptly capitate apically, with short hairs. Proboscis dark brown, short. Gena narrow. Thorax: Dark grey pruinose with green and bronze reflections especially dorsally, setae black. Mesoscutum moderately arched, prescutellar depression present. Proepisternum with minute seta. Postpronotal lobe with 2 minute setae. Mesonotum longer than wide. Acrostichal setae absent; other thoracic setae well differentiated, each side of mesonotum with: 4 dorsocentrals, 1 presutural supra-alar (posthumeral), 1 postsutural supra-alar, 2 notopleurals, 1 postalar. Scutellum broadly subtriangular with 1 long, strong, dorsally projected seta per side. Mesopleuron bare. Halter pale brown. Legs: Evenly brown, except apex of fore coxa yellow; with mostly short setae; tarsomeres 1–4 of all legs progressively shorter apically with tarsomere 5 slightly longer than 4; tarsomere 5 of all legs with very weakly developed dorsomedial process; tarsal claws, pulvilli and empodium normally developed on all legs. Foreleg: Coxa apparently with short, sparse pale setae on anterior surface, apical margin with setae longer; femur, tibia and tarsus subequal in length; tarsomere 1 subequal to combined length of tarsomeres 2–4. Midleg: Coxa with a few pale setae; femur subequal in length to tibia, with row of anteroventral setae (subequal in length to femur width); tarsus slightly longer than tibia; tarsomere 1 partially obscured from view. Hindleg: Coxa with 2 pale setae on lateral surface; femur, tibia and tarsus subequal in length; tarsomere 1 subequal to combined length of tarsomeres 2–3. Wing (Fig. 22): With brownish tinge, veins dark brown, about 2.5X longer than wide. Pterostigma absent, membrane entirely covered with minute microtrichia, alula absent. Costa circumambient. Extreme anterior base of costa apparently with 1 strong anterodorsal seta (broken in unique holotype) and at least 1 shorter proximal seta. Anterior section of costa (between base and R 2+3) with double row of relatively widely spaced spine-like setae. Posterior section of costa (beyond R 2+3) with setae finer, longer and more closely spaced. Radial and medial veins M 1 and M 4 complete and reaching wing margin, M 2 and CuA+CuP (anal vein) absent, Sc faint. R 1 short, terminating near basal 1/3 of wing. Base of Rs originating opposite humeral crossvein. R 2+3 subparallel with R 1 in basal part, subparallel with R 4+ 5 in distal part. R 4+5 weakly sinuous. M 1 straight in basal half, sinuous in distal half and curving posteriorly to costa apically. M 4 mostly straight with posterior curve to costa apically. CuA rounded. Short r-m crossvein present in basal portion of wing, distal to base of R 4+5. Crossvein bm-m incomplete. Cell dm, base of M 2 and dm-m crossvein absent. Cells br, bm and cua in basal fourth of wing. Cell cua closed, ovoid. Anal lobe not developed. Calypter with fine setae. Abdomen: Brown with small dark setae (weaker and pale on sternites); sternite 6 mainly bare, segment 7 bare. Segments 5–7 narrowed and laterally compressed to form cavity on right side for hypopygium. Sternite 5 lacking pregenitalic process. Sternite 8 ovoid, with short setae; tergite 8 indistinct. Hypopygium (Figs 23–25): Concolorous with pregenitalic abdominal sclerites; lateroflexed to right; inverted with posterior end directed anteriorly; small and compact, about 1/4 length of abdomen; asymmetrical; foramen not formed. Epandrium divided into left and right lamellae. Left epandrial lamella (Fig. 23) partially overlapping left side of hypandrium, posterior margin trifurcate, ventrally fused with hypandrium but margin distinct; ventral epandrial process apparently not articulated at base, long and slender, projected dorsally, tip with weak weakly ventral bend. Left surstylus bilobed, dorsal and ventral lobes separated by U-shaped cleft through which left postgonite lobe protrudes. Dorsal lobe of left surstylus with short apical seta, long preapical dorsal seta, and short dorsal seta, lacking prensiseta. Ventral lobe of left surstylus longer than dorsal lobe, narrow with relatively short setae ventrally. Right epandrial lamella (Fig. 24) partially overlapping right side of hypandrium, ventrally fused with hypandrium but margin distinct, slightly longer than hypandrium, with prominent seta near middle of posterior margin; ventral epandrial process present, narrow and strongly upcurved. Right surstylus bilobed, dorsal and ventral lobes separated by U-shaped cleft through which right postgonite lobe protrudes. Dorsal lobe of right surstylus broad with short apical seta, long preapical dorsal seta and short dorsal seta, lacking prensiseta. Ventral lobe of right surstylus about 3X longer than dorsal lobe, with 1 ventral seta near middle and 1 preapical medial seta. Hypandrium bowl-shaped, slightly shorter than epandrium in lateral view. Left postgonite lobe large, deeply bilobate, with thumb-like dorsomedial lobe and longer ventral lobe (Fig. 23). Right postgonite lobe shorter than left lobe, apically bilobate with ventral lobe about as long as dorsomedial lobe (Fig. 24). Phallus tubular, J-shaped, projected dorsally, with flange-like ventral projection near base, with tip not expanded. Ejaculatory apodeme keellike. Hypoproct bifid with narrow dorsal lobe and longer broader ventral lobe, left and right sides symmetrical (Fig. 25). Cercus subtriangular in dorsal view (Fig. 25), with small preapical seta and 2 prominent dorsal setae, left and right cercus symmetrical.
Female: Body length 1.30 mm, wing length 1.40 mm. Similar to male except as follows: Abdomen (Fig. 21): Tapering posteriorly, apical segments retracted into segment 5. Terminalia with tergite 8 medially divided, narrowly fused with sternite 8 anterolaterally; syntergite 9+10 medially divided with 4 acanthophorous spines on each side; cercus with narrow, upturned and pointed tip, with short ventral setulae; spermathecal duct an unsclerotized tube with broad ridged sperm pump in basal part (terminal part lost in dissected female).
Distribution. This new species is known only from the type locality along Rivère Bleue in the Yaté Commune of the South Province of New Caledonia (Figs 8–10).
Etymology. The specific epithet refers to the riparian habit of the new species (Figs 9, 10).
Remarks. Formerly, Cumming & Brooks (2019) included this exemplar species (i.e., “ New Caledonia sp.”) as a member of “Undescribed genus [New Caledonia]” in their phylogenetic analysis of the Parathalassiinae, because presence of female terminalia with acanthophorous spines was not considered typical of Chimerothalassius at that time. The type series of C. riparius sp. nov. was collected together with the holotype of C. sinclairi sp. nov. in yellow pan traps placed along the margin of Rivère Bleue.
description: Published as part of Brooks, Scott E. & Cumming, Jeffrey M., 2022, New Australasian Parathalassiinae (Diptera: Dolichopodidae sensu lato), pp. 521-543 in Zootaxa 5188 (6) on pages 528-530, DOI: 10.11646/zootaxa.5188.6.2, http://zenodo.org/record/7103618