Cheilosia (Cheilosia) vansteenisi Bot, Mengual, Meutter & Skevington, 2025, sp. nov.

Cheilosia (Cheilosia) vansteenisi sp. nov. urn:lsid:zoobank.org:act: C7EDACEF-AE70-4B0C-87FF-50B8AA0661E3 Figs 75–76 Differential diagnosis Cheilosia vansteenisi sp. nov. is morphologically and genetically very close to C. aerea. The easiest character to distinguish them is the pile on the posterodorsal corner of the anterior anepisternum: pilose in C. aerea, but bare in C. vansteenisi. Other differences are the darker legs in C. vansteenisi, which are black, except for the base and apex of protibia and mesotibia in the male which are dark brown (in C. aerea tibiae are extensively yellow at base and apex), scutum slightly finer punctured and terga shinier (tergum III almost entirely shiny in C. vansteenisi vs extensively pruinose medially in C. aerea). Moreover, male of C. vansteenisi sp. nov. has the face with denser pruinosity (Fig. 76A) and the frons with dense pruinosity; the female of C. vansteenisi, on the other hand, has the frons pruinose in anterior part (shiny in C. aerea), postpedicel black (Fig. 76B) (usually in C. aerea at least basoventral corner dark orange) and terga with only very few black pile in posteromedial parts of terga III–IV (in C. aerea with extensive black pile medially on terga II–IV). Our new species is similar to species of the proxima group (Vujić et al. 2013), and within that group closest to C. proxima, but smaller (7–7.5 mm vs 7–9 mm) and with darker legs (Fig. 75A, C) (in C. proxima, tibiae usually distinctively yellow at base). The male has denser pruinosity on face (Fig. 76A), frons, postpronotum and terga with more and denser pruinosity, scutum medially with an area of short black pile at the level of wing bases (Fig. 75A) (short black pile on this area is missing in C. proxima), terga and sterna on average with less black pile, sterna less densely pruinose with shiny spots on sterna I–II (sterna I–II entirely pruinose in C. proxima), surstylus with field of microtrichia (Fig. 76D) (absent in C. proxima) and dorsal lobe of postgonite long and pointed with straight dorsal margin (Fig. 76C) (in C. proxima the lobe is shorter and less pointed and the dorsal margin has an extension). The female of C. vansteenisi sp. nov. has the frons extensively pruinose in anterior part (shiny in C. proxima), scutum with shorter and more adpressed pile, terga II–III shinier and tergum IV with yellow pile (medially with black pile in C. proxima). Etymology This new species is named after Jeroen van Steenis, our friend and the collector of the paratype. We name this species after him to acknowledge his immense contribution to the study of Syrphidae. Species epithet to be treated as a noun in the genitive case. Material examined Holotype GEORGIA • ♂; Racha-Lechkhumi and Kvemo Svaneti, Tsana; 42.9160° N, 43.1428 E; 1975 m a.s.l.; 19 Jun 2019; X. Mengual leg.; ZFMK, ZFMK-TIS-8008772 = ZFMK-DIP-00066391. Paratype GEORGIA – Samegrelo-Zemo Svaneti • 1 ♀; Mestia; 43.02° N, 42.89° N; 2600 m a.s.l.; 13 Jun. 2019; J. van Steenis leg.; JSB, 2019-01.121, ZFMK-TIS-8009610. Description Male LENGTH. Body 7.5 mm, wing 7 mm. HEAD. Face bare, with distinct facial tubercle, black, densely pruinose, below lunule narrower than an eye; parafacia black, pruinose, white pilose. Clypeus pruinose, about one and a half times as long as wide. Frontal triangle black, pruinose, long black pilose. Length of eye contiguity about 1.2 the length of frons. Angle of approximation of eyes ca 90°. Vertical triangle black, shiny, ocellar triangle shiny, long black pilose and with few shorter yellow pile. Occiput pruinose, short yellow and long black pilose. Lunule dark yellow, with distinct medial arm, separating acetabula. Scape black, anteriorly with black and yellow setae; pedicel black, anteriorly with black setae; postpedicel blackish, pruinose, about as wide as high; arista black, with short pile, pile much shorter than diameter of arista at base. Eye with dense, yellow pile. THORAX. Scutum black, shiny, except postpronotum densely pruinose and notopleural area slightly pruinose, finely punctured, with long yellow pile, intermixed with sparse often longer black pile, black pile dominant only in anterolateral corners, posteriorly in the center with field of short erect black pile. Scutellum shiny, with long erect yellow pile and sparse erect black pile intermixed, and long black setae along posterior margin. Pleura black, slightly pruinose; anterior anepisternum bare; pile on pleura white except in posterodorsal corner of posterior anepisternum with few black pile and setae; katepisternum continuously pilose. Haltere yellow. WING. Wing including alula entirely microtrichose, hyaline, veins dark brown. LEGS. Coxae and trochanters black. Femora, tibiae and tarsi black except base and apex of protibia and mesotibia dark brown; profemur with mixed black and yellow pile; mesofemur with yellow pile; metafemur with anterodorsal and anteroventral long yellow pile, ventrally with short black setae; tibiae and tarsi with black and yellow pile. ABDOMEN. Tergum I pruinose, tergum II pruinose except lateral and posterior margins, tergum III pruinose anteriorly, pruinosity decreasing, from the anterior margin of tergum III towards the middle of the tergum, tergum IV shiny except narrow strip medially along anterior margin; terga with long erect yellow pile, pile shorter in center of terga II–III, except sparse short black pile intermixed in center of posterior half of tergum II and center of tergum III. Sterna I–IV pruinose except center of sterna I–II with shiny spot; sterna with long erect yellow pile, except along posterior margin of sternum II and in center of sterna III–IV where pile adpressed. Genitalia with surstylus 1.3 times as long as wide, and with large field of microtrichia on lamella (Fig. 76D); dorsal lobe of postgonite long and pointed (Fig. 76C). Female LENGTH. Body 7 mm, wing 7 mm. Similar to the male, except for normal sexual dimorphism and the following characters. Posteroventral corner of face and genae with orange spot. Frons with mixed yellow and black pile. Frons shiny except anteriorly where pruinose. Occiput pruinose except shiny behind dorsal eye corner. Occiput yellow pilose. Scutum with semi-adpressed yellow pile, in center of posterior part mixed with black pile. Scutellum with short yellow pile. Pile on pleura yellow. Legs black. Femora with yellow pile. Terga shiny except tergum I and the center of anterior margin of tergum II. Terga with yellow pile, except tergum II posteriorly in center with small area of black pile and tergum III medially with large triangular area of black pile. Sterna I–IV pruinose. Genetics Both DNA barcodes from the holotype and paratype cluster together with high support (BS = 100%). Remarks We consider the species rare, with only two specimens collected during three expeditions in three different years in the same area. Biology Collected in mountains between 1975–2600 m a.s.l. Distribution So far only known from the type series localities in the Greater Caucasus in Georgia.

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