Taxonomic revision of the Neotropical genus Argentinomyia Lynch-Arribálzaga, 1891 (Diptera: Syrphidae), with description of 16 new species Author Montoya, Augusto L. 0000-0003-3307-034X aleon.montoya@udea.edu.co Author Wolff, Marta 0000-0002-3389-7083 martha.wolff@udea.edu.co text Zootaxa 2023 2023-02-03 5234 1 1 157 http://dx.doi.org/10.11646/zootaxa.5234.1.1 journal article 53225 10.11646/zootaxa.5234.1.1 be77753c-0c7a-4f90-a020-f23b778d06d0 1175-5326 7609993 A540F250-BDE2-43F7-83A1-DA261F914B41 Argentinomyia spinifemorata Montoya sp. nov. Proposed standard English name: Spiny femur long-antennae flower fly. ( Figs 6E , 76 and 90B ) Type material. HOLOTYPE . Adult female, pinned, deposited at Museo Entomológico Francisco Luis Gallego. Original label: “ COLOMBIA , Santa Elena” / “en Barbecho, 6.210509 , -75.498419 ” / “ 2546 m , x.1965 , R. Vélez ”. “ HOLOTYPE / Argentinomyia spinifemorata / Montoya 2023” ( MEFLG 27270 ). Length (n= 1): Body, 5.8 mm ; Wings, 5.3 mm . Diagnosis. Sides of face orange golden pollinose and pilose, tubercle with two transversal grooves, with a median dash of pollen extending from antennae almost to the tubercle; frontal triangle with a brown velvet cross band golden pilose; scutum aeneous grey, punctulate, with three brownish vittae on anterior half, a median slender brown vitta extending along the thorax, in addition to a lateral wider brownish vitta, widening towards the pronotum and narrow near the pre-scutellum; metafemur swollen, with ventral spines reaching the anterior 1/2; terga 3 rd to 5 th with basal transversal fascia. Description. FEMALE. Head ( Fig. 76A ): Face black, sides of face orange golden pollinose and pilose; tubercle low with at least two transversal grooves, with a median dash of pollen extending from antennae almost to the tubercle. Gena black, covered with yellow pollen and pile. Ocellar triangle opaque, with a brown velvet cross band golden pilose. Occiput golden pollinose and pilose. Antennae, yellow, short, ratio 1.0:1.2:2.6; basoflagellomere brown dorsal, longer, a little longer than scape and pedicel together; arista yellow at base and dark on apical third, slightly pilose. Thorax ( Figs 76B–C ): Aeneous grey, punctulate, yellow pilose and pollinose; with three brownish vittae on anterior half, a median slender brown vitta extending along the thorax, in addition to a lateral wider brownish vitta, widening towards the pronotum and narrow near the pre-scutellum. Pleura shining aeneous, grey pollinose, pile whitish and sparse. Scutellum punctulate, shining greenish-brassy to aeneous. Wing ( Fig. 76C ): Slightly yellowish, stigma orange-brownish, microtrichose, except cell c bare on basal 4/5, cells bm and r bare on basal 4/5, respectively, cell cua bare on anterior 1/2, basicosta orange, orange pilose, except for some black pile; calypter brown, border and fringe yellow; plumula yellow; halter yellow, capitulum yellow. Legs ( Figs 6E , 76C, E ): yellow, except the metafemur brown, only slightly yellow apically, metafemur swollen, with ventral spines reaching the anterior 1/2; basal three segments of pro-, meso- and metatarsi yellow, the apical ones black; pile yellow, coxae brown. Abdomen ( Figs 76B, D ): Abdomen narrowed toward the base, 2 nd tergum with a pair of lateral rounded maculae, covering the entire lateral margin but attenuated posteriorly; 3 rd to 5 th terga with basal transversal fascia, reaching apical 1/4, 1/4 and 1/3 respectively, pile yellow. MALE. Unknown. FIGURE 76. Argentinomyia spinifemorata sp. nov. , female Holotype (MEFLG 27270): A. Head, frontal view; B. Dorsal view; C. Lateral view; D. Vista posterodorsal. Scale bars: 5 mm. E. Posterior leg, detail of ventral spines (Black arrows indicating ventral spines). Scale bars: 2 mm. Etymology. The epithet “ spinifemorata ” is an adjective derived from the Latin “ spinei ”, spine, thorn, backbone (Brown 1956: 738) and the Latin “ femur ”, thigh: femur, femoral (Brown 1956: 468) and the Latin suffix - atus , provided with, having the nature of, pertaining to. It refers to the metafemur with ventral spines of this species. Remarks. Argentinomyia spinifemorata sp. nov. is unique within Melanostomini , characterized by having the metafemur swollen, with ventral spines reaching the anterior 1/2 ( Figs 6E , 76C, E ). Within Syrphinae , the metafemur of Salpingogaster Schiner, 1868 (tribe Syrphini ) has a distinct row of ventral spinose bristles on apical 1/2, but the metafemur is not swollen. The presence of enlarged metafemur and ventral spines is common in groups of Eristalinae , including several variations. In Sterphus Philippi (Milesiini, Xylotina) the metafemur has a line of strong ventral spiny setae, meanwhile, in Spilomyia Meigen (Milesiini, Milesiina) the metafemur has a single small ventroapical spine (calcar, apicoventral extension). For its part, in Lepidomyia Loew, 1864 (Brachyopini, Brachyopina) the metafemur has strong ventral (small) spiny setae in the pro-, meso- and metafemur (Thompson 1999; Thompson et al. 2010 ). A marked sexual dimorphism in the shape of metafemur has also been recorded in Brachypalpus Macquart and Chalcosyrphus Curran ( Eristalinae, Milesiini, Xylotina ), where the female metafemur is less swollen, ventrally with rows of reduced spines, more developed in males than in females (Jeonga et al. 2017). These dimorphic features play a key role in mating, through which the male can hold the female during mating and/or elicit tactile responses which are critical to the cascade of cues and counter cue that lead to successful mating ( Rotheray & Gilbert 2011 ). In this context, a sexual dimorphism could be expected for A. spinifemorata sp. nov. , in such a case, the male conspecific may have a very swollen metafemur and strong ventral spines, compared to those evidenced in the female. However, we are aware that this appreciation will remain speculative until the male is discovered and described, considering also the fact that the type specimen was collected 76 years ago and despite exhaustive sampling efforts being carried out near the type locality, non-additional specimens have been found, which could be probably due to the rarity of this species (for a complete discussion of rarity see Montoya et al. 2022 ) or its potential local extinction due to the increase in deforestation in the Andean region of Colombia in the last years. However, our remarkable discovery opens new questions about how these characteristic posterior leg modifications originated and evolved within Syrphinae , particularly in Melanostomini . In this sense, more intensive sampling efforts and targeted fieldwork are needed to unravel the many issues surrounding this rare species. Taxonomic notes. Although A. spinifemorata sp. nov. is described from a single female ( Figs 6E , 76 ), we evidenced that the species differs significantly from the A. berthae ( Fig. 18D – F ), A. fastigata ( Fig. 30D – F ), A. festiva ( Fig. 32D – F ) and A. lanei ( Fig. 40D – F ) by the unique metafemur swollen, with ventral spines reaching the anterior 1/2. The apparently restricted distribution raises the need for further expeditions to neighboring areas of the type locality in order to increase the knowledge about the species distribution and population dynamics as well as find male specimens to be described. Geographical range. Argentinomyia spinifemorata ( n= 1) is known only from the Holotype , which was collected in a forest area of Medellín ( Colombia ) at an altitude of 2546 m ( Fig. 90B ). The species is endemic to the Northern Andes domain at middle altitudes ( 2546 m ) in the Magdalena province .