Coenosia chaetosa Malloch, 1934

Patitucci, Luciano Damián, Couri, Marcia Souto & Mulieri, Pablo Ricardo, 2021, The killer flies Coenosia Meigen (Diptera: Muscidae) of southern South America: the Coenosia chaetosa species group with two new species, and notes on male terminalia patterns, Journal of Natural History 55 (23 - 24), pp. 1499-1519 : 1505-1507

Coenosia chaetosa Malloch, 1934

For a complete list of references, see the catalogue by de Carvalho et al. (2005). Subsequent information to this catalogue: Coenosia chaetosa . Löwenberg-Neto et al. 2011 (biogeography), Löwenberg-Neto and de Carvalho 2013 (checklist).

Male. Length. Body: 3.19–3.57 mm, wing: 3.52–3.70 mm.

Head ( Figure 2 (a, b)). Frons, fronto-orbital plate, parafacial and gena black with brownish-grey pollinosity. Frons longer than wide, with frontal triangle short, not reaching lunula, visible with shifting reflections according to the direction of light (birefringence). Gena with strong black hairs, and with height less than the width of the postpedicel. Arista with its longest microtrichia hardly longer than its basal diameter.

Thorax ( Figure 2 (c)). Black with grey pollinosity, with two fine dark-brown vitta along dorsocentral row of setae. Chaetotaxy: acrostichal setae short and strong, the anterior presutural pair as long as the eaDC; dorsocentrals 1 + 3, with an eaDC seta, less than one third of the aDC; intra-alars 1 + 2, postsutural setae similar in length; supra-alars 1 + 2, the posterior seta very short. Katepisternum with 2–3 setula. Wing. Tegula yellow.

Legs. Coxae black with grey pollinosity and black setae. Trochanters reddish brown with black setae. Femora black with grey pollinosity, apex of all femora and all tibia yellow, tarsus black. Mid femur with a row of fine ventral setae, 2 strong setae on anterior surface, and 2 preapical setae on posterodorsal to posterior surface; mid tibia with one anterodorsal and one posterodorsal median setae, anterodorsal seta longer and positioned below of the posterodorsal seta. Hind femur with a complete row of anterodorsal and a row of anteroventral setae on apical half.

Abdomen ( Figure 2 (d)). Grey with square lateral dark-brown marks on tergites 3–5. Sternite 5 with similar width and lenght, basal margin convex, apical margin strongly concave (‘V’ shape), without a membrane; setae concentrated on the lobes not extended to basal margin ( Figure 2 (e)).

Terminalia. Cercus longer than broad with a slight constriction on apical third, sclerotised, setulose (hair-like seta), with apical margin concave with 2 strongly sclerotised teeth ( Figure 2 (f-h)). Surstyli longer than broad, slightly curved at the distal tip towards cercus ( Figure 2 (g, i)). Hypandrium tubular, longer than wide, with lateral prolongations, distal extreme not exposing the phallapodeme. Aedeagus with phallapodeme straight, strongly sclerotised, and a little longer than hypandrium in lateral view; pregonite developed, kidney-shaped, ventrally fused with the hypandrium; postgonite developed; epiphalus slightly sclerotised, and distiphallus tubular, and slightly sclerotised at base ( Figure 2 (j-k)).

Female unknown.

Type material. Holotype male, pinned, damaged. http://data.nhm.ac.uk/object/ 8e084b8e-63cc-49af-8937-d282366f88b1

Other specimens examined. ARGENTINA: Chubut: PNLP: 20 males, Intendencia , −42.085077, −71.614662, I-2011, Mulieri & Patitucci leg . ( MACN). Neuquén: 1 male, Lago Moquehue , 10-II-2018, −38.962947, −71.347913, Mulieri leg . ( MACN).

Distribution ( Figure 3 (a)). ARGENTINA: Chubut (new record), Neuquén (new record). CHILE: Región de Valparaíso.

Remarks. Malloch (1934) described C. chaetosa with a single male specimen from Los Andes, Chile. For this species, this author highlights the presence and development of the presutural acrostichal and dorsocentral setae. The number of the presutural dorsocentral setae in Coenosiinae (one or two setae) and the interpretation of the second one (as seta or setula) have been analysed in different ways. All Coenosiinae have a developed aDC (generally with the same length as the postsutural dorsocentral setae), which is placed in the anterior half of the prescutum. The ground-plan state in Muscidae includes two presutural dorsocentral setae, being the absence or reduction of the second presutural dorsocentral seta (pDC), placed in the posterior half of the prescutum, a character observed in Coenosiinae ( Couri and Pont 2000) . Some Coenosiinae species present a second or extra anterior presutural dorsocentral seta (eaDC), located anterior to the developed aDC. Both setae are in the anterior middle half of the prescutum. In previous works focused on Coenosia , the presence of eaDC was studied in different ways. Malloch (1934) compared for C. chaetosa the size of the eaDC in relation to the prestural acrostical setae, and observed that eaDC setae are very close to the aDC. Other authors mentioned the eaDC as an ‘accessory presut dc setulae’ ( Snyder 1957), or just compared with the size of the aDC ( Gregor et al. 2002). Sorokina (2009) presented an interesting discussion on the presence and size of this character for the genera Macrochis Rondani and Dexiopsis Pokorny , currently synonymous with Coenosia . Important to mention that other Coenosiinae genera, as the endemic Apsil Malloch and Reynoldsia Malloch of the Subantarctic sub-region, present this eaDC ( Malloch 1934). A detailed study with a phylogenetic analysis could give more information on this character.

Figures

Figure 2. Coenosia chaetosa, male. (a) Lateral view (Scale bar = 1 mm). (b) Head, frontal view. (c) Thorax, dorsal view. (d) Abdomen, dorsal view (Scale bar = 0.5 mm). (e) Sternite 5 (Scale bar = 0.2 mm). (f) Cercus and surstyli, posterior view. (g) Cercus, surstyli, and phallic complex, lateral view (Scale bar = 0.5 mm). (h) Detailed of distal tip of cercus (SEM). (i) Detailed of distal tip of surstylus (SEM) (Scale bar = 0.02 mm). (j) Phallic complex, lateral view. (k) Detailed of distal tip of phallic complex (SEM) (Scale bar = 0.05 mm). (Abbreviations: eaDC, extra anterior dorsocentral seta; aDC anterior dorsocentral seta; distiph, distiphallus; epiph, epiphallus; hypd, hypandrium; hypd lat, lateral prolongation of hypandrium; pgt, postgonite; phapod, phallapodeme; pregt, pregonite).

Figure 3. Geographical distribution. (a). Coenosia chaetosa Malloch. (b). Coenosia mallochi sp. nov. (c). Coenosia metalleg sp. nov. (Violet area: Central Chilean subregion; green area: Subantarctic subregion; black circle: new records; red square: previous distribution.).