Empis (Enoplempis) arthritica Melander
Creators: name: Sinclair, Bradley J.
name: Brooks, Scott E.
name: Cumming, Jeffrey M.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Empididae
Empis
Empis arthritica

description: Empis (Enoplempis) arthritica Melander
(Figs 6 A, B, C, 7A, 11A)
Empis arthritica Melander, 1902: 318. Type locality: Montgomery County, Pennsylvania, USA. Empis (Enoplempis) arthritica: Melander, 1928: 142.
Type material examined. LECTOTYPE (here designated in order to fix identity of the species) ♂, labelled: “Montg[omery]Co/ 5.26.95 [26.v.1895] PA”; “W.W. Wheeler,/ Collection”; “ TYPE / No./ A.M.N.H. [red label]”; “Am. Mus. Nat. Hist./ Dept. Invert. Zool./ No. 961”; “ LECTOTYPE / Empis / arthritica Mel. / des. Sinclair, Brooks, Cumming 2012 [red label]” (AMNH). PARALECTOTYPES: Same data as lectotype (3 ♀, AMNH); same data as lectotype, except C.W. Johnson Collection (2 ♂, 2 ♀, USNM).
Additional material examined. USA. Missouri: McDonald Co., nr Lanagan, 8.v.1984, G.P. & J.F. Hevel (1 ♂, USNM). Pennsylvania: Dauphin Co., Grantville, 24.v.1962, J.G. Chillcott (3 ♂, CNC); Hummelstown, 25.v, C.W. Johnson (1 ♂, 1 ♀, USNM). Tennessee: Knoxville, v (09), J.M. Aldrich (1 ♂, 1 ♀, USNM). Virginia: Bedford Co., NF Goose Ck, Mile 90.2 Blue Ridge Pkwy, 29.v.2006 (1♂, CSUC); Giles Co., Mountain Lake, 3600 ft., 28.v.1962, J.G. Chillcott (2 ♂, CNC): Giles Co., New River, 17.v.1997, S.A. Marshall (1 ♂, DEBU); Montgomery Co., Brush Mt., Blacksburg, 2800 ft., ex. blossoms of Rubus alleghaniensis, 27.v.1962, J.R. Vockeroth, J.G. Chillcott (5 ♂, 7 ♀, CNC).
Diagnosis. This species is distinguished by the highly modified processes of the hind femur and tibia, including tufted setose process on anterior face of the femur.
Re-description. Wing length 6.3–6.7 mm. Male. Head dark in ground-colour, with dense grey pruinescence on face, frons and occiput. Dichoptic, eye with ommatidia of similar size. Frons divergent towards antennae; below ocellar triangle as wide as or slightly wider than anterior ocellus, bearing short setulae along inner margin of eye. Face slightly divergent towards mouthparts; bare with oral margin dark and shining. Ocellar triangle with grey pruinescence, with pair of short parallel ocellar setae; posterior setulae lacking. Occiput bearing row of postocular setae, stout and black on upper section; shorter and more slender on lower section; occipital setae black, long and stout, subequal in length to upper postocular setae. Postpedicel, stylus and scape mostly dark; extreme base of postpedicel and inner face of pedicel slightly paler or orange-brown. Scape slightly more than 2× longer than pedicel; postpedicel more than 5× longer than basal width, more than 3× longer than stylus. Palpus yellow, with setulae dark. Proboscis largely yellow; apex of labrum reddish brown; labellum with dark setae.
Thorax dark in ground-colour, largely densely grey pruinescent. Scutum with pair of distinct dark vittae between acr and dc rows; pair of distinct vittae lateral to dc and above notopleural depression. Pleura grey, often with paler upper parts of katepisternum, anepimeron, laterotergite and meron. Proepisternum with several short, dark setae; prosternum bare. Antepronotum with row of short stout dark setae. Postpronotum paler than scutum, with 4–8 short, dark setae and 1 long seta. Scutum with sparse row of fine acr setulae; dc similar to acr, increasing in length posteriorly; 1 posterior npl, with several anterior npl setae; 1 presut spal; 1 psut spal; 1 pal. Scutellum with pair of short sctl, shorter than pal, lacking marginal setulae. Laterotergite with 3–4 long dark setae. Anterior and posterior spiracles pale.
Legs long, entirely yellow, except for dark ring at trochanter-femur junction and apices of femora; apex of tarsomere 1 and tarsomeres 2–5 reddish brown. Coxae with numerous dark lateral setae, longer and stouter along apical anterior margins. Hind trochanter lacking setae. Femora lacking distinct posteroventral row of setae; hind femur thickened towards apex. Fore tibia clothed in long dark setae, shorter than width of tibia; with 3–5 anterodorsal, 2–5 posteroventral and several preapical setae. Mid tibia clothed in long dark setae, shorter than width of tibia; several anterodorsal setae, 4 or more posteroventral and anteroventral setae and several preapical setae. Hind femur with short preapical anteroventral process, bearing tuft of stiff black setae, with 3 anteroventral setae distal to process (Figs 6 A–C); inner apex with preapical posteroventral hook-shaped process directed ventrally, short, preapical, posterior finger-like knob and anteroventral apex produced as flange. Hind tibia somewhat twisted, geniculate and highly excavated at base, fitting posteroventral processes of femur when reflexed (Fig. 6 A); outer base with short anteroventral knob with tuft of stiff, black setae, opposite tufted process of femur; inner base with posteroventral thumb-like process, apex attenuated, densely clothed in setae; anterodorsal and dorsal portions with several rows of stout, black setae of various lengths, some subequal to width of tibia; several preapical setae present. Tarsomeres 1–5 of all legs with rows of antero- and posteroventral spine-like setae; fore tarsomere 1 somewhat swollen, similar in size to hind tarsomere 1.
Wing clear with brownish veins; all veins complete (except Sc), well sclerotized. Basal costal seta short, inconspicuous, slightly stouter and longer than surrounding costal setae. R5 and M1 somewhat divergent near wing margin; R5 ending beyond wing tip; radial fork acute. Halter yellow.
Abdomen yellow with median area of tergites dark, sternites yellow; long marginal setae on tergites. Marginal setae on segment 8 subequal to length of tergite. Pregenital segments unmodified; sclerites of segment 8 weakly fused laterally, forming complete ring, weakly sclerotized dorsally. Terminalia (Fig. 7 A) largely yellow. Cercus broad, well separated from dorsal margin of epandrium, posterior end prolonged into finger-like, setose process arched medially. Hypoproct lacking setae. Epandrial lamella subrectangular, posterodorsal margin produced into hook-like process (lacking pubescence) with bacilliform sclerite extending to base of process; setae short. Hypandrium short, not extended posteriorly with truncate margin, about 0.2× as long as epandrium; lacking setae. Phallus with broad basal 0.3, apical 0.6 gently arched dorsally and gradually tapered; apex emerging beyond cercus; ejaculatory apodeme longer than half length of epandrium; inverted Y-shaped, with median keel reduced.
Female. Similar to male, except as follows: frons slightly broader; hind femur and tibia lacking modified setae and processes; cercus long and slender, slightly shorter than tergite 8.
Geographical distribution and seasonal occurrence (Fig. 11 A). Empis (En.) arthritica ranges along the Appalachian Mountains from Pennsylvania to Tennessee, west to the Ozark Plateau in Missouri. Adults have been collected throughout May.
Nuptial gift presentation. Form unknown.
description: Published as part of Sinclair, Bradley J., Brooks, Scott E. & Cumming, Jeffrey M., 2013, Revision of the Empis subgenus Enoplempis Bigot, east of the Rocky Mountains (Diptera: Empididae), pp. 401-456 in Zootaxa 3736 (5) on pages 412-415, DOI: 10.11646/zootaxa.3736.5.1, http://zenodo.org/record/248431