Empis (Enoplempis) tridentata Coquillett

Sinclair, Bradley J., Brooks, Scott E. & Cumming, Jeffrey M., 2013, Revision of the Empis subgenus Enoplempis Bigot, east of the Rocky Mountains (Diptera: Empididae), Zootaxa 3736 (5), pp. 401-456 : 444-448

Empis (Enoplempis) tridentata Coquillett

( Figs 1 G, 2B, 19D, 21A, 22B)

Empis tridentata Coquillett, 1901: 609 . Type locality: Pennsylvania, USA.

Type material examined. LECTOTYPE (here designated in order to fix identity of the species) ♂, labelled: “Delaware Co/ 6[June].12.94 PA”; “CW Johnson/ Collector”; “ Type / No. 5491/ U.S. N.M. [red label]”; “ Empis / tridentata / Coq.” [dissected]; “ LECTOTYPE / Empis tridentata Coquillett / des. Sinclair, Brooks &/ Cumming 2013 [red label]” (USNM). PARALECTOTYPE: Same data as holotype (1 ♀, USNM).

Taxonomic notes. This species was based on two males and one female specimen, collected by C.W. Johnson. There are two males in the USNM with the same data as the lectotype, either of which could be the third syntype. Both lack the original type label found on the other two syntypes. The designation of the lectotype clearly establishes the identity of this species.

Additional material examined. CANADA. Quebec: Berthierville, 28.vi.1938, J. Ouellet (1 ♀, AMNH); Cté Vaudreuil, summit Mt. Rigaud, 16.vii.1993, D.M. Wood (1 ♀, CNC); Terrasse Vaudreuil, Molson Nature Reserve, MT, 16–25.vi.1999, S.E. Brooks (1 ♂, CNC). USA. Connecticut: Stamford, 5.vi.1936, B.T.R. Lab. Col. (1 ♀m USNM). Georgia: Forsyth Co., 2.vi.1970 (6 ♂, 1 ♀, CNC). Maryland: Beltsville, flowers of Viburnum dentatum , 18.vi.1916, W.L. McAtee (1 ♂, 2 ♀, USNM); Beltsville, 28.vi.1917, flowers of Xolisma ligustrina, L.O. Jackson (1 ♀, USNM); Laurel, 11.vi.1965, marsh edge (2 ♀, CNC); Laurel, 1.vii.1965, MT (1 ♀, CNC); nr Laurel, 20.vi.1967, D.R. Smith (3 ♂, 1 ♀, USNM). Massachusetts: Amherst, 24.vi.1963, D. Meissner (1 ♂, USNM); Melrose Highlands, 1.vii.1911, J.D. Tothill (1 ♂, CNC); Middlesex Co., Lincoln, 6,12. vii.1982, E.T. Armstrong, MT, (9 ♂, 1 ♀, USNM). Mississippi: Lafayette Co., Spring 1943, iv–v.1946, F.M. Hull (10 ♂, 6 ♀, CNC); Tishomingo Co., Tishomingo State Park, Outcroppings Tr., waterfall, 34°36'32''N 88°10'31''W, 20.v.2013, J.M. Cumming (2 ♂, CNC); same locality except: stream at Pioneer Cabin, 34°36'19''N 88°11'36''W, J. Gelhaus, #1507 (1♀, CNC); Winston Co., Tombigbee NF, Spring Seep, along sandbottom str., MT, 33°15'18''N 89°05'29''W, 17–21.v.2013, J.M. Cumming (1♂, 1♀); Winston Co., Noxubee NWR, Loakfoma Ck at Dummy Line Rd, MT, 33°15'09''N 88°50'53''W, 17–21.v.2013, J.M. Cumming (1♀, CNC). New Hampshire: Same data as holotype (2 ♀, AMNH; 4 ♂, 3 ♀, USNM); Durham, 1.vii.1981, K. Tacewski (1 ♀, CNC); Grafton Co., Bridgewater, Whitmore Pt. on Newfound Lk, 26.vi.1998, 43.65°N 7.77°W, 27.vi.–5.vii.2004, MT, S.D. Gaimari (3 ♂, 1 ♀, CSCA); Hillsborough Co., Nashua, Long Hill, 20 m, 42°42'59''N 71°27'04''W, 27.vi.–5.vii.2004, MT, S.D. & A.V. Gaimari (14 ♂, 9 ♀, CNC). New Jersey: Long Branch, 9.vi.1913, C.W. Johnson (1 ♀, USNM): Woodbury, 27.vi.1896, C.W. Johnson (1 ♂, USNM). New York: Long Is., East Marion, 20.v.1929, R. Latham (1 ♀, CUIC). Oklahoma: Latimer Co., 4 mi SW Red Oak, 20.v.1993, J.M. Cumming (2 ♀, CNC). Pennsylvania: Roxborough, 14.vi.1908, C.T. Greene (1 ♂, USNM). Rhode Island: Westerly, 6.vii.1936, M. Chapman (1 ♂, USNM). South Carolina: Lexington Co., Lexington environs, yellow pans forest, 22– 30.iv.2000, L. Masner (3 ♀, CNC). Texas: Shelby Co., Sabine NF, Boles Field, 304 ft., 23.iv.1990, Baumann & Nelson (1 ♂, CNC). Tennessee: Lynchburg, 26.v.1976, F.C. Harmston (1 ♂, CAS).

Diagnosis. This is one of the most distinctive species of this subgenus with patterned wings, three dark scutal vittae and darkly banded abdomen.

Re-description. Wing length 5.0– 6.6 mm. Male. Head dark in ground-colour, with dense greyish pruinescence on face, frons and occiput. Dichoptic, eye with ommatidia of equal size. Frons divergent towards antennae; below ocellar triangle as wide as anterior ocellus, distinctly narrower at middle; setulae absent along inner margin of eye. Face slightly divergent towards mouthparts; bare with oral margin pale and shining. Ocellar triangle dark, subshining, with pair of slightly divergent ocellar setae. 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; postgena with white silky hairs. Postpedicel, stylus and scape mostly dark; base of postpedicel and pedicel often slightly paler or orange-brown. Scape slightly more than 2× longer than pedicel; postpedicel length slightly less than 3× basal width, 2.5× longer than stylus. Palpus bright yellow, with setulae dark. Proboscis yellow; apex of labrum reddish brown; labellum with pale setae.

Thorax yellow in ground-colour, largely densely white pruinescent. Scutum with 3 distinct blackish vittae along acr and dc rows, acr vitta broader than dc vittae, coalescing in prescutellar depression. Pleura yellow, usually with darker shading posterior to spiracles, anterior to laterotergal setae and on ventral pleura. Proepisternum with several long, silky white setae; prosternum bare. Antepronotum with row of short, stout dark setae. Postpronotum with 3 dark setae and several short setae. Scutum with biserial row of fine acr setulae; dc increasing in length posteriorly, prescutellar seta subequal to sctl; 3 posterior npl, with several anterior npl setae; 1 presut spal; 1 psut spal; 1 pal. Scutellum with 2 pairs of long sctl, outer pair shorter. Laterotergite with 3 long dark setae and numerous long white silky setae. Anterior and posterior spiracles pale.

Legs long and stout, entirely yellow, except for dark ring at trochanter-femur junction and apices of femora; apical tarsi darker. Coxae with numerous dark lateral and apical setae, longer and stouter along apical anterior margins; anterior setae white, silky. Hind trochanter lacking modified setae. Fore femur inflated, wider than remaining femora; lacking rows of dark setae. Mid and hind femora with stout anterior preapical seta and several additional preapical setae; anteroventral row of spine-like setae present; mid femur with posteroventral row of black spine-like setae of various lengths, mostly confined to apical half; hind femur with poorly refined rows of short, black posteroventral setae ( Fig. 19 D). Fore tibia clothed in short fine setae; lacking stout erect setae, except for 3–4 anterodorsal setae and several preapical setae. Mid tibia clothed in short fine setae; 2 antero- and 2 posterodorsal setae, 1–3 posteroventral and several preapical setae. Hind tibia clothed in short fine setae; 4 antero- and posterodorsal setae ( Fig. 19 D) and several preapical setae. Tarsomeres 1–5 of all legs with rows of antero- and posteroventral spine-like setae; fore tarsomere 1 slender, not swollen and lacking long outer setae.

Wing with clouding at base of R4, apex of discal cell, r-m crossvein, apex of basal cells and branching of Rs (Fig. 2B); all veins complete (except Sc), well sclerotized. Basal costal seta very long, subequal to outer sctl; 3 long black setae at ventral wing base. R5 and M1 divergent near wing margin; R5 ending before wing tip; radial fork acute. Halter yellow.

Abdomen with broad, dark anterior band on tergites; tergites with dark marginal setae and clothed in shorter white setae. Marginal setae on segment 8 shorter than length of sclerites. Pregenital segments unmodified; sclerites of segment 8 widely separated, not fused, tergite weakly sclerotized anterodorsally. Terminalia ( Fig. 21 A) largely yellow. Cercus short, broad, separate from anterior margin of epandrium, broader at anterior end; posterior end truncate; clothed in setae, subequal in length to posterior width of cercus. Hypoproct with pair of slender, fingerlike projections extending to either side of phallus. Epandrial lamella subquadrate, posterior margin somewhat truncate, bearing short apical setae. Hypandrium very reduced, with rounded apical margin, about 0.5× as long as epandrium; lacking setae. Phallus with broad base, tapered, apical half sinuous; apex emerging beyond cercus; ejaculatory apodeme shorter than epandrium; inverted Y-shaped, with short median keel.

Female. Similar to male, except as follows: frons broader, as wide as ocellar triangle; spine-like setae of mid femur less numerous and slightly less stout; abdominal pleural membrane extensive and slightly darkened on segments 2–5, probably eversible; cercus long and slender, slightly shorter than tergite 8.

Geographical distribution and seasonal occurrence ( Fig. 22 B). Empis (En.) tridentata is a widespread species, ranging from west of the southern Mississippi river basin, north to southern Quebec. In the northern part of its range, it is apparently not found west of the Appalachian Mountains, except for outliers in the Laurentians. Adults of E. (En.) tridentata have been collected from late April to mid-July.

Nuptial gift presentation. Form unknown.

Remarks. Females have an extensive darkened abdominal pleural membrane that is probably eversible. This is usually considered a secondary sexual feature in female Empidinae , which is correlated with female swarming and sex-role reversal involving male choice (Cumming 1994).

Figures

FIGURE 1. Empis (Enoplempis) species. A, B, E. vockerothi (Hocking Co., OH) male with balloon (photographs by Allen Coovert); C, swarming males of E. vockerothi with balloons shown by arrows (photograph by Allen Coovert); D, E. snoddyi (Sevier, TN) apparently in the process of forming a balloon (photograph by Thomas Bentley, copyright Thomasbentley. com); E, E. vockerothi, male; F, E. appalachicola, male; G, E. tridentata, male. Scale bars = 2 mm.

FIGURE 19. Male legs of E. (Enoplempis). A, E. snoddyi, hindleg, anterior view; B, E. stenoptera, hindleg, anterior view; C, E. stenoptera, hind trochanter, anterior view; D, E. tridentata, hindleg, anterior view; E, E. vockerothi, hindleg, anterior view.

FIGURE 21. Male terminalia, lateral view of E. (Enoplempis). A, E. tridentata; B, E. vockerothi.

FIGURE 22. Distribution of E. (Enoplempis). A, E. snoddyi and E. stenoptera; B, E. tridentata.