Anabarhynchus sigatoka, Irwin & Winterton, 2019

Irwin, Michael E. & Winterton, Shaun L., 2019, A new stiletto fly in the genus Anabarhynchus Macquart (Diptera: Therevidae) from Fiji, Zootaxa 4700 (3), pp. 385-393 : 386-391

Anabarhynchus sigatoka sp. n.

(Common name: ‘Sigatoka stiletto fly’) [ urn:lsid:zoobank.org:act:FADB4585-13A2-4EDC-A62C-66C6D60E8015 ]

( Figs 1–6 )

Type material. Holotype male, FIJI: Sigatoka province : Vita Levu, Sigatoka Sand Dunes National Park, Malaise trap in coastal beach forest, M.E. Irwin, E.I. Schlinger, Moala Tokota’a, 10m, 9.vii.2003, 18°10’S, 177°30’E ( MEI0162523 ) (California State Collection of Arthropods).

Paratypes. FIJI: Sigatoka province: male, Vita Levu, Sigatoka Sand Dunes National Park , Malaise trap in coastal beach forest, M.E. Irwin, E.I. Schlinger, Moala Tokota’a, 10m, 9.vii.2003, 18°10’S, 177°30’E ( MEI0152597 ) ( California State Collection of Arthropods ) ; female, Vita Levu, Sigatoka Sand Dunes National Park , Malaise trap in coastal beach forest, M.E. Irwin, E.I. Schlinger, Moala Tokota’a, 10m, 9.vii.2003, 18°10’S, 177°30’E ( MEI0163534 ) ( Bishop Museum Natural History ) ; female, Vita Levu, Sigatoka Sand Dunes National Park, Malaise trap in coastal vegetated dune nr. hill top, M.E. Irwin, E.I. Schlinger, Moala Tokota’a, 100m, 23.ix–8.x.2002, 18°10’S, 177°30’E ( MEI0141314 ) (California State Collection of Arthropods)

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Additional material examined. FIJI: Sigatoka Province : female, Vita Levu, 1.1 km SSW Volivoli Village, Sigatoka Sand Dunes, 13-27.ix.2004, 55m, Malaise trap, S. Niusoria, -18.169°, 177.485° ( FBA500248 ) (specimen in poor condition in ethanol) (Bishop Museum Natural History) .

Diagnosis. Frons flat with robust dark setae; antennae directed anteroventrally; prosternum and posterior surface of mid coxa without setal pile; setae present dorsally on metanepisternum; single posterodorsal (pd) macroseta on forefemur; two notopleural, one dorsocentral and one scutellar macrosetae pairs; costal margin with biseriate rows of dark setae; katepisternum and prosternal furrow without setal pile; female sternite 8 with posterior process deeply inserted into sclerite and surrounded by demelanised area.

Description. Body length: ca. 8.0–9.0 mm. Head. Frons wider than ocellar tubercle at narrowest point (slightly narrower in male), antennal base positioned very low on frons; eye facets uniform size throughout; frons flat, glossy black-brown, overlain with silver-grey velutum pubescence laterally, glabrous oblong-shaped area medially flanked by a row of robust, black, downward directed setae laterally; parafacial and face overlain with silver pubescence; ocellar tubercle slightly raised, black and overlain sparse grey pubescence; occiput convex, covered with dense silver-grey pubescence, with scattered irregularly arranged black postocular setae; gena black, densely overlain with silver-white pubescence admixed with long, pale setae; lower angle of eye margin black pubescent and slightly raised; palpus yellow, labellum brown, both with scattered pale setae; frons projecting such that antennae are directed anteroventrally in same plane as frons; antenna with scape as long as pedicel and flagellum combined, scape thicker than flagellum, cylindrical and slightly tapered, dark brown with silver pubescence admixed with robust black setae dorsally and ventrally (setae larger and fewer in number in male); pedicel and flagellum dark yellow, suffused with dark brown basally, short dark setae on pedicel and base of flagellum; flagellum tapered, style elongate. Thorax. Scutum glossy black-brown, overlain with sparse silver-grey pubescence, denser anterolaterally and anteriorly as narrow dorsocentral stripe, admixed with short, pale setae; scutellum glossy black and overlain with sparse grey pubescence, scutal macrosetae (bristles) dark; pleuron and coxae glossy dark brown-black, overlain with sparse to dense silver-grey pubescence as three bands: anteriorly comprising proepimeron and forecoxa, middle band comprising anepisternum, katepisternum and midcoxa, posterior band comprising anatergite, katatergite, metanepisternum and hind coxa; pale setae on proepimeron, anepisternum, katatergite, dorsally on metanepisternum and anterior surfaces on fore and mid coxae; prosternum and posterior surface of midcoxa without setae; few dark macrosetae on coxae; hind coxal knob present; legs yellow with brown suffusion basally on fore and mid femora; tibiae darker distally, fore femur with one dark posterodorsal seta; all femora with sparse dark appressed setae; all tibiae and tarsi with dark macrosetae; haltere dark yellow-tan, dark apically; wing smoky infuscate, veins yellow-tan basally, darker throughout rest of wing, wing cell m 3 open; scutal chaetotaxy (pairs): np, 2; sa, 2; pa, 1; dc, 1; sc, 1. Abdomen. Dark brown anteriorly and dorsally, light brown to yellow laterally, sparse setae on all segments, pale setae on anterior segments, darker on posterior segments, posterior margins of tergites 2–3 with dark greyish; silver pubescence laterally on all tergites and extensive on segment 1; terminalia with elongate pale setae dorsally, darker ventrally. Male genitalia Epandrium ( Fig. 5A ) slightly longer than wide, narrowed posteriorly; tergite 8 broad; hypandrium barely evident as band along anterior margin of gonocoxites; gonocoxites separate ventrally, extended prominently into rounded processes posteroventrally (=outer gonocoxal process) ( Fig. 5A, E ), numerous elongate setae along posterior surface; gonocoxal apodeme greatly reduced; inner gonocoxal process with apex spatulate with apical setae; gonostylus elongate, apex arcuate, pale elongate setae on medial surface; ventral lobe reduced, narrow; aedeagus with parameral sheath sclerotized ( Fig. 5 C,D ), distiphallus strongly curved ventrally at base; dorsal apodeme of parameral sheath ‘Y’-shaped; ventral apodeme forked, lateral ejaculatory apodeme narrow, band-like, ejaculatory apodeme broad anteriorly. Female terminalia ( Fig. 6 ) with sternite 8 with posterior process deeply inserted into sclerite and surrounded by demelanised area; spermathecal sac large, rounded and not lobed.

Etymology. The species epithet is derived from the Sigatoka sand dunes where this species is found.

Comments. Anabarhynchus sigatoka sp. n. represents the first record of any stiletto fly from Fiji. All specimens known were collected from Vita Levu in the Sigatoka sand dunes system ( Figs 7–8 ). This new species is easily placed in the genus by the presence of both a small patch of setae on the metanepisternum and a single macroseta posterodorsally on the forefemur, among other characters typical of Anabarhynchus , although it does exhibit several unique features suggesting a rather isolated position in the genus. The scutal chaetotaxy typical of members of Anabarhynchus is 3 or more notopleural, 2 supra-alar, 1 post alar, 3 or more dorsocentral and 2 or more pairs of scutellar macrosetae. Anabarhynchus sigatoka sp. n. has only two notopleural, and one pair each of dorsocentral and scutellar macrosetae. The orientation of the antennae on the head, angled anteroventrally in line with the angle of the frons in profile is rather unusual and is shared with species such as A. doncollessi Ferguson. Based on the general habitus and chaetotaxy of this new Fijian species, we find that A. sigatoka sp. n. is most likely placed in the ‘ocypteraeformis’ species-group of Lyneborg (2001). The presence of just a single pair of scutellar macrosetae is also found in the two closely species of this species group, which are described from northern Australia, i.e., A. ocypteraeformis Lyneborg and A. striatifrons Lyneborg ( Lyneborg, 2001). Anabarhynchus sigatoki sp. n. also shares characters with members of the ‘ocypteraeformis’ species group such as: the posterior lobe of the female sternite 8 is deeply inserted into the sclerite and surrounded by a de-melanised area, two rows of frontal macrosetae, and a laterally compressed and sub-parallel sided abdomen. It does differ in that the male gonocoxites are separate medially as two sclerites and the female furca is closed posteriorly. An additional undescribed species from Papua New Guinea has a similar habitus to A. sigatoka sp. n. (unpublished data). Biogeographically, the nearest species is the New Caledonian A. hyalipennis varicinctus (Bigot) , but these two species show little morphological similarity suggesting a distant evolutionary relationship (the latter placed in the ‘ hyalipennis’ species-group). Winterton et al. (2015) included A. sigatoka sp. n. in their phylogeny of Therevidae (as Anabarhynchus sp. ‘Fiji’) and recovered the species within Anabarhynchus in a polytomy with Australian species such as A. annulatus and A. maritimus .

Figures

FIGURE 1. Anabarhynchus sigatoka sp. n., male, oblique view (Body length= 8.0 mm).

FIGURE 2. Anabarhynchus sigatoka sp. n., male, lateral view (Body length= 8.0 mm).

FIGURE 3. Anabarhynchus sigatoka sp. n. A. female head, anterior view, B. male head, anterior view (head width = 0.9 mm).

FIGURE 4. Anabarhynchus sigatoka sp. n. male genitalia. A. ventral view; B. epandrium; C. dorsal view with epandrium removed; D. lateral view with epandrium removed.

FIGURE 5. Anabarhynchus sigatoka sp. n. male genitalia. A. gonocoxites, ventral view; B. epandrium; C. aedeagus, dorsal view; D. aedeagus, lateral view; E. gonocoxites, lateral view. Abbreviations: d, distiphallus; da, dorsal apodeme of parameral sheath; ea, ejaculatory apodeme; ga, gonocoxal apodeme; gs, gonostylus; igp, inner gonocoxal process; ogp, outer gonocoxal process; lea, lateral ejaculatory apodeme; va, ventral apodeme of parameral sheath; vl, ventral lobe of gonocoxite. Scale line= 0.2 mm.

FIGURE 6. Anabarhynchus sigatoka sp. n.: female genitalia. Abbreviations: ag, accessory gland; f, furca; sd, spermathecal duct; sdd, spermathecal sac duct; s, spermatheca; ss, spermathecal sac; s8, sternite 8.

FIGURE 7. Habitat of Anabarhynchus sigatoka sp. n.; Vita Levu, Sigatoka sand dunes, (photo copyright: Stephen D. Gaimari).

FIGURE 8. Habitat of Anabarhynchus sigatoka sp. n.; Vita Levu, Sigatoka sand dunes, dunes dominated by Ipomea pescaprae (L.) R. Br. (Convolvulaceae) and various grasses (photo copyright: Stephen D. Gaimari).