Eulonchus marginatus Osten Sacken, 1877

Borkent, Christopher J., Gillung, Jessica P. & Winterton, Shaun L., 2016, Jewelled spider flies of North America: a revision and phylogeny of Eulonchus Gerstaecker (Diptera, Acroceridae), ZooKeys 619, pp. 103-146 : 112-114

Taxon classification Animalia Diptera Acroceridae

Eulonchus marginatus Osten Sacken, 1877 Figs 3, 4, 5, 16A, 17B, 18B, 19B

Eulonchus marginatus Osten Sacken, 1877: 277

References.

Osten Sacken 1878: 99 (catalogue); Aldrich 1905: 221 (catalogue); Kertész 1909: 12 (catalogue); Cole 1919: 38 (key notes, figs), 1923: 46 (California); Sabrosky 1948: 388 (key); Cole 1969: 221 (notes); Poole 1996: 36 (checklist).

Common name.

Sombre Sapphire or Emerald.

Diagnosis.

Proboscis straight, approximately reaching apex of abdomen; ocellar tubercle trifurcate; legs dark brown (pale ‘knee’ joint); calypter margin black or brown.

Redescription.

Body length: 7.2-11.4 mm, wing length: 5.2-9.5 mm. Head. Flagellum dark brown; scape and pedicel brown, male flagellum cylindrical, shorter than head height; clypeus elongate, extending beyond oral cavity, shape rounded with flat area dorsally, clypeus black-brown, glossy with sparse pubescence; labial palp brown, extending anteriorly beyond proboscis at point of attachment; margin of oral cavity (parafacial) pilose, admixed with short pubescence; ocellar tubercle trifurcate, processes narrow (anteromedial process taller), height taller than width; median ocellus greatly reduced or absent; occiput metallic green-blue, metallic blue or metallic purple, pile densely white or yellow. Thorax. Metallic green, blue or purple, setal pile erect, white or yellow; coxae black with metallic blue sheen; femora dark brown, apices white; tibiae brown (whitish basally on dorsal surface); tarsi brown; calypter margin light to dark brown, membrane translucent, with suffused brown marginally; haltere stem dark brown, knob lighter brown. Abdomen. Metallic olive green, green or blue-violet, vestiture white or yellow, dominant setae erect, pile posteriorly directed, marginal band of laterally directed pile on T2-4. Male genitalia. Epandrium round, with posterior margin concave; gonocoxite with anterior margin almost straight, with large fenestrae; aedeagus heavily sclerotized laterally, with a secondary dorsal point just prior to the opening of the aedeagus.

Type material examined.

Holotype male, MCZ, "Napa Co/ California." [white]; "O. Sacken./ West Dipt." [white]; "Type/ 1078" [red and white]; " Eulonchus / marginatus / O.S." [white]"; "Eug-Dec 2006/ MCZ Image/ Database" [white]; " MCZ-ENT/ 00001078" [white]; "HOLOTYPE ♂/ Eulonchus marginatus / Osten Sacken/ Det. C.J. Borkent 2015" [red]; specimen condition: excellent, no parts missing. Body length: 8.9 mm, Wing length: 7.0 mm.

Other material examined.

Listed in Table 3 (Suppl. material 1).

Distribution

(Fig. 20). Nearctic: Northern California (USA).

Ecology.

Eulonchus marginatus has been recorded visiting the flowers of 10 different plant families and 14 different species (Table 2).

Biology.

Host unknown.

Comments.

Eulonchus marginatus is closely related to Eulonchus tristis , sharing features such as extensive white thoracic pile and dark colouration on the legs. Eulonchus marginatus is easily distinguished from other species in the genus by the leg colour, trifurcate ocellar tubercle and dark margin of the calypter. This species displays considerable variation in body colour, ranging from metallic green, blue to purple.