Eulonchus tristis Loew, 1872

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 : 121-127

Taxon classification Animalia Diptera Acroceridae

Eulonchus tristis Loew, 1872 Figs 13, 14, 15, 16C, 17F, 18F, 19F

Eulonchus tristis Loew, 1872: 60.

References.

Osten Sacken 1877: 276 (California), 1878: 99 (catalogue); Melander 1902: 181 (California, Idaho, notes); Howard 1902: pl. 18, fig. 23 (habitus); Aldrich 1905: 221 (catalogue); Kertész 1909: 12 (catalogue); Woodworth 1913: 152 (California); Peterson 1916: 181, Figs 284a, 364a, 425a, 425b and 543 (head capsule, mouthparts); Cole 1919: 34, pl. 5, fig. 18 (habitus) (key, notes, Idaho, British Columbia, Oregon, California), 1927: 422, fig. 86 (male genitalia); Cole and Lovett 1921: 239 (Oregon); Essig 1926: 559 (descr. note, Idaho, Oregon, California); Brunetti 1926: 583 (Idaho); Sabrosky 1948: 390 (key ref., notes); Schlinger 1965: 404 (catalogue), 1969: 221, fig. 134 (notes), 1987: 320 (host); Poole 1996: 36 (checklist); Coyle and Icenogle 1994 (larval host).

Common name.

Dusky Sapphire.

Diagnosis.

Proboscis reaching apex of abdomen; ocellar tubercle trifurcate with three ocelli present (median smaller than laterals); legs mostly dark brown ( ‘knee’ pale), calypter margin dark and membrane white or light yellow.

Redescription.

Body length: 7.9-12.8 mm, Wing length: 6.0-11.2 mm. Head. Flagellum dark brown, scape and pedicel brown, male flagellum cylindrical, shorter than head height; clypeus elongate, extending beyond oral cavity, rounded with flat area dorsally, black-brown, surface glossy, glabrous; labial palp brown, length extending anteriorly beyond proboscis at point of attachment; margin of oral cavity (parafacial) pilose admixed with pubescence (faint); proboscis length from middle of abdomen or extending beyond abdomen; ocellar tubercle trifurcate, processes subequal (narrowly digitate), height equal to or shorter than width; median ocellus present, greatly reduced or absent; occiput metallic green-blue, blue or purple, pile densely white or yellow. Thorax. Metallic green, blue or purple, setal pile white or yellow; coxae brown or black with metallic blue sheen; femora dark brown, apicies white; tibiae dark yellow or brown; tarsi dark yellow; calypter margin dark brown or light brown, membrane translucent; haltere entirely dark brown. Abdomen. Metallic olive green, bright green to blue-violet, vestiture white or yellow, dominant setae appressed or erect, pile posteriorly directed, marginal band of dense thicker setae on T3-4, or posteriorly directed, marginal band of laterally directed pile on T2-4. Male genitalia. Epandrium round, with posterior margin almost straight; gonocoxite as tall as wide, with anterior margin almost straight, with large fenestrae; aedeagus heavily sclerotized laterally.

Type material examined.

Lectotype male (designated here), MCZ, "S. Francisco/ H. Edw" [white]; “Loew” [white]; "Type/ 3/ 1077" [red and white]; " MCZ-ENT/ 00303280" [white]; "LECTOTYPE ♂/ Eulonchus tristis / Loew/ Des. C.J. Borkent 2015" [red]; specimen condition: tarsi of right mid leg and left flagellum missing, membrane of both wings slightly damaged on posterior portion. Body length: 9.8 mm, wing length: 9.2 mm. Paralectotype female, MCZ, "S. Francisco/ H. Edw." [white]; “Loew” [white]; "Type/ 2/ 1077" [red and white]; " MCZ-ENT/ 00303279" [white]; "PARALECTOTYPE ♀/ Eulonchus tristis / Loew/ Det. C.J. Borkent 2015" [yellow]; specimen condition: very good, tarsi of right hind leg missing. Paralectotype female, MCZ, "S. Francisco/ H. Edw" [white]; “Loew” [white]; "Type/ 4/ 1077" [red and white]; " MCZ-ENT/ 00303281" [white]; "PARALECTOTYPE ♀/ Eulonchus tristis / Loew/ Det. C.J. Borkent 2015" [yellow]; specimen condition: very good, left mid and hind legs missing. Paralectotype male, MCZ, " Californ/ Edwards" [white]; “Loew” [white]; " Eulonchus / tristis Lw./ Cant. X" [white]; "Type/ 1077" [red and white]; " MCZ-ENT/ 00001077" [red and white]; "Aug-Dec 2006/ MCZ Image/ Database" [white]; "PARALECTOTYPE ♂/ Eulonchus tristis / Loew/ Det. C.J. Borkent 2015" [yellow]; specimen condition: very good, flagella missing.

Other material examined.

Listed in Table 3 (Suppl. material 1).

Distribution

(Fig. 20). Nearctic: Northern California, Oregon, Washington, Arizona.

Ecology.

Pollen loads and diversity from individual Eulonchus tristis visiting flowers of Brodiaea elegans ( Themidaceae ) and Iris douglasiana ( Iridaceae ) in California has been studied, showing high levels of constancy to a single species (Borkent and Schlinger 2008 b). Eulonchus tristis has been recorded visiting the flowers of 19 different plant families and 38 different species (Table 2).

Biology.

Host: Aliatypus sp. ( Antrodiaetidae ) ( Schlinger 1987).

Comments.

Eulonchus tristis is most similar to Eulonchus marginatus , with which it shares the ocellar tubercle trifid and the flagellum half as long as the head. Eulonchus tristis can be easily distinguished from Eulonchus marginatus by its femur and tibia with yellow markings and the pile on abdomen yellow.