Peradon oligonax (Hull)

Reemer, Menno, Skevington, Jeffrey H. & Kelso, Scott, 2019, Revision of the Neotropical hoverfly genus Peradon Reemer (Diptera, Syrphidae, Microdontinae), ZooKeys 896, pp. 1-93 : 1

Peradon oligonax (Hull) Figs 1 , 30 , 110 , 111 , 228-231 , 264

Microdon oligonax Hull, 1944: 35. Holotype ♀: Brazil (CU) [examined]; Thompson et al. 1976: 66 [type locality erroneously stated as Ecuador].

Peradon oligonax (Hull): Reemer and Ståhls 2013a: 146; Marín-Armijos et al. 2017: 185.

Studied type specimens.

Brazil • 1 ♀, holotype of Microdon oligonax Hull; Pto. America, R. Putumayo; 30 Aug. -2 Sep. 1920; Cornell University Expedition leg.; CU. Label 1: "Pto. America, R. Putumayo BRAZIL, Aug. 30 Sep. 2 ‘20”; label 2: "Cornell Univ. Expedition. Lot 569"; label 3 (red): "HOLOTYPE Cornell U. No. 2197"; label 4 (red): "Holotype oligonax Hull"; label 5:"Holotype Microdon oligonax Hull".

Additional specimens.

Brazil • 1 ♂; Amazonas, Tabalinga; 11-14 Jul. 1991; Socorro & Vidal leg.; INPA • 1 ♂; Rondonia, 62 km SE Ariquemes; 7-18 Nov. 1995; W.J. Hanson; LACM.

Bolivia • 1 ♂; Songo; RMNH • 1 ♂; La Paz Prov., Mapiri Arroyo Tuhiri; 15°17'26"S, 68°15'46"W; 508 m a.s.l.; 13 Apr. 2004; M. Hauser leg.; CSCA.

Brazil • 1 ♂; Amazon “66.53”; NHMUK.

Colombia • 1 ♂; Vaupes, Mirafiores; 31 Jan. -5 Feb.1972; M. Cooper leg.; NHMUK.

Ecuador • 1 ♂; Pompeya, Napo R., Pastaza; 14-22 May 1965; L. Pena leg.; CNC •1 ♂; Napo, Tena; 9-14 Dec. 1971; M. Cooper leg.; NHMUK.

Peru • 1 ♀; Tingo Maria; 670 m a.s.l.; Weyrauch leg.; CNC • 1 ♂; Previsto; 8 Jun. 1965; J. Schunke leg.; NHMUK • 3 ♂; Previsto; 25 Jun. 1965; J. Schunke leg.; NHMUK • 1 ♂; Previsto; 26 Jun. 1965; J. Schunke leg.; NHMUK • 1 ♀; SAM, around San Roque de Cumbaza; 6°23'4.96"S, 76°25'53.47"W; 15-31 Jan. 2015; T. Faasen leg.; RMNH • 1 ♀; Tingo Maria; 670 m a.s.l.; Weyrauch leg.; CNC.

Redescription

(based on holotype). Adult female. Body size: 16 mm.

Head. Face occupying slightly more than 1/3 of head width in frontal view; yellow; brown pile, except with white pilosity ventrolaterally. Gena brown; with white pilosity. Lateral oral margin strongly produced, brown. Frons black, with black pilosity. Vertex brown; with pale pilosity. Occiput black; with pale pruinescence; black pilosity dorsally, pale pilosity ventrally. Eye bare. Antennal fossa approx. as wide as high. Antenna dark brown, except basoflagellomere black. Antennal ratio approximately 4:1:6. Basoflagellomere parallel-sided with rounded apex. Arista slender, approx. 3/4 of length of basoflagellomere.

Thorax. Mesoscutum dull black; short, appressed black pile. Postpronotum and postalar callus pale brown; mixed black and yellow pilose. Scutellum brown, yellow along posterior margin; brown pilose; with two yellow apical calcars of approx. 1/4 of length of scutellum, with mutual distance ca. four times their length. Pleura brown. Anterior and posterior part of anepisternum separated by deep sulcus; black pilose anteriorly, pale pilose posteriorly, with wide bare area in between. Anepimeron entirely pale pile. Katepisternum white pilose dorsally, bare ventrally. Katatergum and anatergum microtrichose. Other pleurae bare. Calypter and halter yellow.

Wing. Hyaline, tinged yellow on anterior half and all veins yellow; microtrichose, except alula 90% bare leaving only margins microtrichose.

Legs. Fore and mid legs (including coxae and trochanters) yellowish brown, yellow pilose. Hind coxa, trochanter and femur brown, yellow to white pilose. [Hind tibia and tarsus missing in type specimen

Abdomen. Elongate, slightly constricted at segment 2, approx. as wide as thorax, with widest point at anterior part of tergite 4. Sternite 1 brown; bare. Sternite 2 yellow; yellow pile. Sternite 3 yellowish brown; yellow pilose. Sternites 4 and 5 dark brown; dark pilose.

Male (based on additional specimens). As female, except for following differences. Body size 14-15 mm. Antennal ratio approximately 4:1:5. Scutellar calcars shorter and less far apart. Abdomen more slender.

Diagnosis.

Body length: male 13-16 mm, female 16 mm. Based on the somewhat constricted abdomen, this species is here placed in the trivittatus species group. From all other species in this group, P. oligonax differs by the presence of a (medially interrupted) fascia of golden pile along the mesonotal transverse suture (similar to several species of the bidens species group).

Notes.

Colouration varies from reddish brown to blackish. The pale markings on tergite 2 are often fused into one large macula, but sometimes there is a narrow dark median line dividing them. In the specimen labelled 'Amazon / 66.53' (coll. NHMUK) the side margins of tergite 2 are slightly more convex in dorsal view than in the other specimens, in which tergite 2 is more parallel-sided.

Thompson et al. (1976) state Ecuador as type locality, but this seems to be incorrect. Both the label of the holotype and the description of Hull (1944) only mention Brazil (Rio Putumayo) as type locality. This is also discussed by Marín-Armijos et al. (2017).

In the key to the species, Peradon oligonax is included in the trivittatus species group because of its constricted abdomen. However, other characters suggest it may be more closely related to species of the bidens group. For instance, the fascia of golden pile along the mesonotal transverse suture is also found in several species of the bidens group, and there also are similarities in the male genitalia. Unfortunately, attempts to obtain a DNA barcode of this species failed.

Distribution.

Bolivia, Brazil (Amazon region), Colombia, Ecuador, Peru. Alt. 400-860 m.

Figures

Figures 1, 2. Field images of Peradon species. Both photos were taken in Peru, San Martin, around San Ruque de Cumbaza, 15 - 31. I. 2015, by Tim Faasen 1 P. oligonax male 2 P. aurigaster female.

Figures 28 - 31. 28 - 30 Wings of Peradon species: 28 P. elongatus male (Brazil INPA) 29 P. elongatus female (Brazil INPA) 30 P. oligonax female (holotype) 31 Peradon oligonax male (Bolivia RMNH) mesonotum.

Figures 105 - 111. Dorsal habitus of Peradon species (trivittatus group) 105 P. hermetia ♂ holotype 106 ♂ P. hermetoides holotype 107 P. elongatus ♂ Brazil INPA 108 P. elongatus ♀ Brazil INPA 109 P. diaphanus ♀ neotype 110 P. oligonax ♂ Brazil LACM 111 P. oligonax ♀ Peru RMNH. Scale bar: 10 mm.

Figures 228 - 231. Peradon oligonax female, holotype 228 habitus dorsal 229 habitus lateral 230 head frontal 231 head lateral.

Figures 262 - 267. Male genitalia of Peradon species 262 P. hermetoides holotype 263 P. elongatus holotype 264 P. oligonax Colombia NHMUK 265 P. satyricus holotype 266 P. sciarus paratype 267 P. bidens Suriname RMNH.