The metallic Helina viola (Diptera: Muscidae) from Andean Patagonian region

Helina Robineau-Desvoidy, 1830, the second genus of Muscidae in terms of richness, occurs in all zoogeographic regions and comprises more than 540 species (Kim et al., 2023).

The species of Helina inhabiting the southern extreme of South America were studied by Malloch (1934) as part of his revision of the “Diptera of Patagonia and South Chile, part VII, Muscidae”. Recently, Patitucci et al. (2016) presented a taxonomy review of all the species known from the Andean-Patagonian forests. With the exception of Helina viola Malloch, 1934, they proposed four synonyms, and included three new species. All these species have external morphological similarity regarding colour (black with grey or brownish-yellow pollinosity) and chaetotaxy, except for H. viola, which presents blue metallic coloration.

Malloch (1934) described H. viola from a single female specimen collected in “Lago Gutiérrez”, Río Negro province, Argentina. The aim of this contribution is to present the redescription of H. viola based on male and female specimens, with detailed images of the terminalia.

Specimens were collected in “Parque Nacional Nahuel Huapi” (PNNH), as part of the “Darwin Initiative” project (Brooks et al. 2009). A detailed description of the areas studied has been previously presented in Brooks et al. (2009).

Specimens were identified using the original descriptions (Malloch, 1934) and photographs of type specimens. To study the morphology of terminalia, the abdomen of selected specimens was detached and transferred to 90 % lactic acid at room temperature for two weeks. After clearing, the genital structures were removed and temporarily mounted on concave glass slides in glycerin. After the study, the dissected parts were placed in a plastic microvial with glycerin and pinned with the respective specimen. The terminology used for the external morphology follows Cumming & Wood (2017).

Digital photographs were taken using an Olympus DP 25 digital camera mounted on an Olympus SZX 16 stereomicroscope, and a Brunel digital camera mounted on a Motic optical microscope. Images were processed with the Olympus cellSens Standard software and Combine ZM. Measurements were digitally obtained with the Leica Application Suite EZ software Version 2.1.0. Maps were created with the QGIS software 3.40.5 (http://www.qgis.org/pl/site/) and edited with Adobe Illustrator CC. The shapefile used is available at http://www.ign.gob.ar.

All the specimens studied belong to the Museo de La Plata (MLP), and Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN), Buenos Aires, Argentina. High-quality images of type specimens deposited at the Natural History Museum, London, United Kingdom (BMNH) were examined.

Helina viola Malloch, 1934

Helina viola Malloch: For a complete list of references, see the catalogue by Carvalho et al. (2005). Information subsequent to this catalogue: Löwerberg-Neto et al., 2011 (biogeography); Löwerberg-Neto & Carvalho, 2013 (checklist); Patitucci et al., 2016 (key).

Diagnosis. Black with metallic violet pollinosity; presutural acrostichal setae 2-3; dorsocentral setae 2+3-4; prealar present; katepisternals 1+3-5; prosternum and anepimeron bare; veins bare; lower calypter glossiform; legs dark brown; fore tibia setulose on posterior to ventral surfaces; male hind tibia strongly setulose, with a differentiate row of anterodorsal setae, calcar absent.

Description. Male (Fig. 1a). Length. Body: 7.43-8.22 mm, wing: 6.96-7.60 mm.

Head (Fig. 1b). Black with metallic violet pollinosity. Holoptic, the shortest distance between eyes is 0.10-0.26 mm. Inner vertical setae proclinate, outer vertical setae divergent, and postocular setae proclinate. Frontal vitta black; 12-13 pairs of frontal setae. Eye hairs long and numerous. Lunule black; fronto-orbital plate and parafacial black with silver pollinosity. Fronto-orbital plate bare. Postgena and occiput black with metallic violet pollinosity. Gena black with dark brown pollinosity, with black setae. Antenna black; arista bare, in lateral view inserted at the midlevel of the eye. Palpus black, filiform dilated at apex.

Thorax (Fig. 1c). Scutum and scutellum metallic dark violet, without vittae; anepisternum, anepimeron, katepimeron, katepisternum, proepisternum, proepimeron and meron metallic dark violet; anterior and posterior spiracles black. Chaetotaxy: acrostichal setae 2-3+1; dorsocentral setae 2-3+4; intra-alar setae 1+2; supra-alar setae 1+2; basal postpronotal setae 3, the inner one shorter; notopleural setae 2, of similar size, notopleuron bare. Prealar setae strong, half the lenght of the anterior postsutural supra-alar setae. Scutellum with long and strong lateral and apical setae. Anepisternum setulose with a series of 10-14 strong setae, proepisternum, proepimeron setulose, proepisternals 2; proepimerals 2-3; katepisternum setulose, katepisternals 1+3-5; anepimeron, katepimeron and meron bare. Prosternum bare.

Wing. Hyaline with vein brown; veins bare; the transverse cross-vein dm-cu strongly curved; vein R 4+5 and vein M straight; cross vein dm-cu in basal half of cell r4+5. Both calypters hyaline with brown margins; lower calypter glossiform; halter and knob dark brown.

Legs. Dark brown. Fore femur strongly setulose on dorsal to posteroventral surfaces, with a differentiate posterodorsal row setae; fore tibia setulose on posterior to ventral surfaces, and with 3-4 preapical setae. Mid femur setulose on dorsal to posteroventral surfaces, with a differentiate row of ventral setae at the apical third, and 2-3 preapical setae on dorsal to posterior surfaces; mid tibia with 3-5 posterior setae, and 4-5 preapical setae. Hind femur setulose on anterodorsal to ventral surfaces; hind tibia strongly setulose, with a differentiate row of anterodorsal setae (Fig. 1e), calcar absent. Claws and pulvilli with similar size in all three legs.

Abdomen (Fig. 1d). Metallic violet. Sternite 1 bare. Sternites 2-4 setulose, rectangular. Sternite 5 longer than wide; setulose; basal margin slightly concave, apical margin strongly concave, with little setulae extending over two lobes with plush appearance (Fig. 2a).

Pregenital segments. Tergite 6 thin, sclerotized, not fused with syntergosternite 7+8. Syntergosternite 7+8, sclerotized connected through a bridge with sternite 6+7. Right arm of syntergosternite 7+8 not fused with sternite 6+7 (incomplete ring). Sternite 6+7 with posterior margin strongly sclerotized; dorsal tip with a lobe with plush appearance; connected to sternite 5 through a membrane (Fig. 2b-c).

Terminalia. Cercus longer than wide, setulose, with a distal incision and with four poorly developed protuberances at the apex (Fig. 2d). Surstylus broad and straight, without setae on inner surface (Fig. 2e). Hypandrium flat and triangular. Aedeagus with straight, strongly sclerotized phallapodeme, shorter than hypandrium in dorsal view (Fig. 3a); pregonite well developed, kidney-shaped, not fused with hypandrium, postgonite developed, slightly bent downward with setulae (Fig. 3b); epiphallus sclerotized, longer and wider than postgonite in dorsal view (Fig. 3a); distiphallus tubular, sclerotized, with a lateral undulation at the tip (Fig. 3c).

Female (Fig. 4). Length. Body: 5.91-8.00 mm, wing: 6.76-8.51 mm.

Differs from male as follows: Head, dichoptic, the shortest distance between eyes is 0.37-0.38 mm; fronto-orbital plate setulose, with 9-10 pairs of frontal setae; interfrontal cruciate setae absent. Legs. Fore tibia with 2 posterior setae. Mid femur with an anterodorsal row of setae in the basal third; and two rows on anteroventral and posteroventral surfaces. Hind femur with an anterodorsal row of setae, and 3-4 setae in the apical middle of anteroventral surface; hind tibia with 4-6 anteroventral setae, 4-5 anterodorsal setae. Terminalia: intersegmental membrane without microtrichiae. Sternites 6 and 7 without plates; sternite 8 with 2 short slight sclerotized plates, with setulae on the distal margin. Hypoproct rounded, sclerotized and setulose (Fig. 4g). Tergites 6 and 7 divided into 2 parallel sclerotized plates. Tergite 8 with 2 “T”- shape sclerotized plates; epiproct with proximal margin curved, and several strong spines, cercus digitiform and setulose (Fig. 4f). Three spermathecae, ovoid shape (Fig. 4e).

Type material. Holotype female, pinned (BMNH). Type locality: Argentina, Río Negro, Lago Gutiérrez.

https://data.nhm.ac.uk/object/39cb48b5-de45-41cc-80ec-fee32a5c774e/1733270400000

Other specimens examined. ARGENTINA, Río Negro, 2 females, 3 males, PN Nahuel Huapí, Mallín Los Patos, 20-XII-2006/23-I-2007, -41.363472, -71.397305, 1020 m.a.s.l., Garré & Montes de Oca leg., Malaise trap, DWN-31, (MACN and MLP).

Biology. Unknown.

Distribution (Fig. 5). ARGENTINA. Rio Negro.

Remark. Since the premature group classification proposed by Patitucci et al. (2016) for the Helina species of South America, the cercus of H. viola could be included within the pattern associated with the group 1 (cercus with a similar width and length and with two protuberances at the apex).

redalyc-journal-id: 3220