Ocyptamus megafemur Thompson

Mengual, Ximo, Miranda, Gil Felipe G. & Thompson, F. Christian, 2018, Unraveling Ocyptamus and the Baccha legacy (Diptera: Syrphidae): redefinition of groups and new species descriptions, Zootaxa 4461 (1), pp. 1-44: 17-18

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Ocyptamus megafemur Thompson

sp. nov.

Ocyptamus megafemur Thompson  sp. nov.

Figs 47–50View FIGURES 46–54. 46, 114.

Ocyptamus  CR-22 Thompson in litt.

Ocyptamus  08-10 Thompson in litt.

Differential diagnosis. This species belongs to Ocyptamus  sensu stricto. O. megafemur  sp. nov. has a complete yellow face, basoflagellomere large and oval with multiple sensory pits, yellow scutellum with posterior margin black, and dark abdomen with three pairs of round/oval yellow maculae. Male frontal triangle and lunule large. It is very distinguishable from other species by its well-defined mesonotal collar on anterior part of scutum, metafemur swollen and arcuate, and metatibia arcuate.

Description. MALE: Head ( Figs 47–49View FIGURES 46–54. 46). Face narrow, about 1/3 as wide as head, short, about 1/2 as high as eye, yellow, shiny, white pilose; tubercle low, indistinct; gena very narrow, yellow, bare; lunule very large, about 1/ 2 of frontal triangle area, yellow; frontal triangle large, yellow, shiny, black pilose except narrowly yellow pilose along eye margins, bare medially; vertical triangle narrow, short, about 1/2 as long as eye contiguity, black, black pilose, with pile in single row; occiput black, white microtrichose becoming grayish-white microtrichose on dorsal 1/3, white pilose, with pile thick and in 4 rows at notch, with 2 rows and some black thin pile on dorsal 1/4; holoptic; eye contiguity about as long as frontal triangle; scape and pedicel yellow, pedicel with triangular medial extension, black pilose except narrowly yellow pilose on lateral margin; basoflagellomere large, oval, with a semicircular row of sensory pits on lateral surface, brownish black except yellow ventrally, on ventral 1/5 laterally and on ventral 1/2 mesially; antennal ratio 1:1:4.5; arista about 2/3 as long as basoflagellomere. Thorax ( Figs 47, 50View FIGURES 46–54. 46). Postpronotum yellow, yellow pilose; scutum black except yellow on notopleuron and adjacent area posterior to transverse suture and on anterior 1/2 of postalar callus, sparsely black microtrichose, white pilose and with distinct anterior collar of pile; notopleuron produced lateral into distinct process; scutellum yellow except apical 1/5 black, dull, pale pilose with some apical dark pile, with a single row of long ventral pile; pleuron black except yellow on posterior anepisternum and dorsoposterior katepisternum, sparsely grayish microtrichose, yellow pilose; plumula not exceedingly large and white; calypter white; halter yellow. Legs: Coxae black, sparsely white microtrichose, yellow pilose; trochanters orange, pale pilose; profemur yellowish orange except black on posterodorsal 2/3, yellow pilose except black pilose along posteroventral margin on basal 2/3; mesofemur yellowish orange except black on posterodorsal 2/3, yellow pilose; metafemur swollen, slightly arcuate, black except basal 1/6 and apex narrowly orange, yellow pilose except black pilose posteriorly and on apical 1/4; pro- and mesotibiae yellowish orange, yellow pilose; metatibia arcuate, with ventroapical apex produced slightly, black, black pilose; protarsus broad, twice as broad as tibia, yellow, yellow pilose; mesotarsus yellow, yellow pilose; metatarsus yellowish orange, black pilose. Wing: Hyaline except subcostal cell light brownish; microtrichose except basomedially bare; bare on narrow base of subcostal cell, anterior to vein Rs, cell r except  anteroapical 1/3, cell bm except on posteroapical 1/5, cell cup except medially on posterior 2/3, anterior to vein A2; alula large, broader than cell cup, bare. Abdomen ( Figs 47, 50View FIGURES 46–54. 46). Elongate, slightly constricted, narrowest at junction of terga 2 and 3, about 1.5 times as long as thorax; tergum 1 black, dull, white pilose; tergum 2 dull, black with two large mediolateral yellow maculae, which extend over lateral margin, black pilose; tergum 3 black with two large subbasal yellow maculae that are isolated from lateral margin, dull, black pilose; tergum 4 black, with two round basal maculae which are isolated from lateral margin, black pilose; tergum 5 black except lateral and apical margins reddish brown, dull, black pilose; sternum 1 dull, black, long white pilose; sterna 2 and 3 narrow, yellow, yellow pilose; sterna 4 and 5 brownish yellow, yellow pilose. Genitalia: as in Fig. 114.

FEMALE. Similar to male except for frons yellow with a narrow medial black vitta, black pilose; tergum 5 black except for small basolateral yellow areas, black pilose; female genitalia reddish brown, black pilose.

Length (n=1). Body, 15 mm; wing, 11 mm.

Etymology. The epithet megafemur  is a Latin noun in apposition referring to the size of the metafemur.

Geographical distribution. From Mexico (Chiapas), east to Hispaniola and south to Costa Rica.

Type-locality. GUATEMALA: Departamento Quiche, south of Chichicastenango, Molino L. Tesoro, along Río Selapec , 1900 m., 14°55'10.56'' N 91°06'20.52'' W.GoogleMaps 

Material examined. Holotype, male, deposited in the Illinois Natural History Survey ( INHS), Urbana  , Illinois, United States, and labelled: “GUATEMALA: Dpto. Quiche // 14°55.176'N 91°06.342'W // south of Chichicastenango // Molino L. Tesoro, 1900 m // along Rio Selapec // ME Irwin. 20 May 1997 ” “ Schlinger Foundation // Guatemala Expedition // May 1997 ” “ Illinois Nat. // Hist. Survey ” “ Holotype // Ocyptamus megafemur  // Thompson 2013 ” [light red, handwritten] “ USNMENT 00249222 ” [barcode]GoogleMaps  . Paratypes: COSTA RICA  : Costa Rica (1♀ INBio, INBIOCRI 0013917701). DOMINICAN REPUBLIC: Independencia Prov., Parque Nacional Sierra de Bahoruco, RD-138 Caseta no 2, 18°12.549' N 71°32.044' W, 1799 m., 3.vii.2003, D. Perez, R. B. Basterdo & B. Hiero (1♀ USNM, USNMENT 00038693)GoogleMaps  . GUATEMALA  : Dpto. Quiche, Chichicastenango, Pascual Aaj , 14°55.067' N 91°07.006' W, 2200 m., 20.v.1997, M.E. Irwin (1♀ INHS, USNMENT 00249221)GoogleMaps  . MEXICO  : Chiapas, El Triumfo , 100 m., 24.vii.1972, J. Helava (1♂ UNAM)  .

Comments. Ocyptamus megafemur  is of interest due to its swollen arcuate metafemur and arcuate metatibia. Such leg structure is common among the milesine genera in the subfamily Eristalinae  . Also atypical characters present in megafemur  are the large lunule and frontal triangle, as well as the large oval basoflagellomere with multiple sensory pits. This species is part of the Ocyptamus  sensu stricto and is superficially similar to O. gastrostactus  .


Illinois Natural History Survey


Smithsonian Institution, National Museum of Natural History


Universidad Nacional Autonoma de Mexico