Dixa ubiquita, Moulton, John K., 2017

Moulton, John K., 2017, The true identity of Dixa modesta Johannsen (Diptera: Dixidae) resolved: synonymy of Dixa similis Johannsen, designation of the Dixa ubiquita species group, and description of three new easter, Zootaxa 4216 (3), pp. 247-260: 249-253

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http://doi.org/ 10.5281/zenodo.231794

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scientific name

Dixa ubiquita

sp. nov.

Dixa ubiquita  sp. nov.

( Figs 1–2View FIGURES 1 – 5, 6–14View FIGURES 6 – 10View FIGURE 11View FIGURES 12 – 20, 21View FIGURES 21 – 23, 24–28View FIGURES 24 – 28)

Dixa modesta Peters & Cook, 1966: 241  , not Johannsen, 1903: 429 (misidentification of most North American specimens).

Type material. HOLOTYPE, ♂ labeled: “ USA: Macon Co. / Coweeta Hydrological Laboratory / Shope Fork, 800 m / N35°03′37.00″ W83°27′05.10″ / 28.iii.2012 / J.K. Moulton ”; “ HOLOTYPE / Dixa  / ubiquita  / J.K. Moulton [red label]” ( CNC)GoogleMaps  . PARATYPES: Same data as holotype, 4♂ and 5♀ to CNC and 5♂ and 5♀ to USNM.

Additional material examined. USA: AL: LIMESTONE COUNTY, Big Crk @ CR33 (Townsend Ford Rd), nr. Shanghai , N34°50′26.94″ W87°04′40.71″, 7.v.2005, JKM (1L). ARGoogleMaps  : POLK COUNTY, Quachita NF, Gap Crk @ Picnic Area , N34°28′33.07″ W94°07′03.78″, 12.v.2007, JKM (2♂, 10♀). GAGoogleMaps  : BARTOW COUNTY, Mosteller Spr @ Mostellar Spr Rd, Sonoraville , N34°22′58.29″ W84°51′03.89″, 240 m, 17.vii.2013, JKM (10♂, 4♀, 2L)GoogleMaps  . CATOOSA COUNTY, Chickamauga & Chattanooga NMP, Rock Cave Spr   , N34°54′02.39″ W85°15′33.73″, 224 m, 8–9.v.2007, C. Parker & J. Robinson (5♂, USGS). CLARKE COUNTY, Athens , 22.xi.1934, E.E. Byrd (1♂, UGCA)  ; 20.v.1974, B. Freeman (1♂, UGCA); UGA Bot. Gardens, Malaise trap, N33°54′02.79″ W83°22′48.48″, 180 m, 3–9.iv.1976, J.F. MacDonald & R.W. Matthews (1♂, UGCA). FANNIN COUNTY, Sm Spr @ Cooper Crk WMA, N34°44′00.60″ W83°58′19.24″, 588 m, 29.iii.2012, JKM (3♀, 5L)GoogleMaps  . HARRIS COUNTY, Mountain Crk @ Hamilton Rd , N32°48′05.24″ W84°55′18.52″, 11.iv.2011, JKM (1♂, 4♀, 1P, 4L)GoogleMaps  . UNION COUNTY, Brown Mill Crk @ Morgantown Hwy (Rt. 60), N34°44′05.5″ 5 W84°06′13.00″, 626 m, 3.v.2012, JKM (3♂)GoogleMaps  . WALKER COUNTY, Ellison ′s Blue Hole, Crockford-Pigeon Mtn. WMA, N34°42′08.03″ W085°20′20.00″, 17.iii.2012, JKM (12L, 2P); Chattahoochee NF, Johns Crk @ Keown Falls Tr Head, 2.iv.2009, JKM (2♂, 14L); Same data, 18.iii.2012, JKM (11L). KYGoogleMaps  : BELL COUNTY, Cumberland Gap NHP, Tunnel Crk, 28.ix.2005, JKM (1♂); Same data, 3.iii.2008, JKM (2♂, 3L); Shilalah Crk, UV light trap  , N36°39′43.63″ W83°32′36.76″, 948 m, 28.ix.2005, C.R. Parker (5♂, USGS). LETCHER COUNTY, Big Everidge Crk, Lilly Cornett Woods, ex. Rt 1103, UV light trap, N37.077° W82.99°, M. Floyd (4♂, 1♀)GoogleMaps  . METCALF COUNTY, Dry Frk, 14.vii.2008, M. Floyd (1♀); Same data, 6.x.2008, M.A. Floyd (2♂); Spring Run #1  , KHLCF Site , 6.x.2008, M. Floyd (3♂, 1♀)  . WOLF COUNTY, Red R Gorge Geol Area, Trib Red R nr Suspension Bridge, ex. Sheltowee Trace Tr , N37°49′28.20″ W83°37′26.70″, 218 m, 9.vi.2015, B.J. Sinclair (4♂, 5♀). LA: JACKSON PARISH, Schoolhouse SpgsGoogleMaps  , N32°27′15.58″ W92°25′57.78″, 75 m, 6.iv.2010, JKM (6♂, 13♀, 1P, 12L). NY: ESSEX COUNTY, Wilmington , 21.viii.1941, A.L. Melander (2♂; UMSP)  . TOMPKIN COUNTY, Ithaca, Fall Crk (Flat Rock), v.19 (02)?, Lot 1294, O.A. Johannsen (1♂; CUIC)  . NC: BUNCOMBE COUNTY, Black Mtns., Lots 1288 & 1297, O.A. Johannsen (1♂; CUIC). HAYWOOD COUNTY, Blue Ridge Parkway NP; ANSP, Woodfin Cascade   , N35°27′08.30″ W83°06′10.60″, 16.vii.2006, JKM & G.R. Curler (9♂; ANSP). Great Smoky Mountains NP, Cataloochie Section, Beech Crk @ Palmer Crk TrGoogleMaps  , N35°38′04.60″ W83°09′07.60″, 1323 m, 21.v.2015, R. Pivar & G. Phillips (14♂, 7♀; ANSP); Rough Fk , N35°36′58.53″ W83°07′13.53″, 862 m, 20.vi.2007, JKM (1♂; ANSP)GoogleMaps  ; 17.iii.2014, JKM (3L; ANSP). W Frk Pigeon R @ NC Rt 215, 12.vi.2008, JKM (3♂). HENDERSON COUNTY, L Cove Crk @ Green R Cove Rd , N35°16′18.68″ W82°18′39.78″, 313 m, 17.v.2013, JKM (5♂, 6♀, 5L)GoogleMaps  . MACON COUNTY, Highlands, Clear Crk , 914 m  , N35°1.5′ W83°11.5′, 2.vii.1958, J.L. Laffoon (2♂; ISIC); Shope Fork, Coweeta Hydrological Lab, Otto , N35°03′37.00″ W83°27′05.10″, 28.iii.2012, JKM (10♂, 10♀, 22L); Coweeta Hydrologic Lab, Coweeta Crk nr confl Ball CrkGoogleMaps  , N35°03′ W83°25′, 680 m, Malaise trap, 5–11.iv.2008, G.W. Courtney (2♂, 1♀, ISIC). SWAIN COUNTY, GSMNP, Seep above campsite #62, Noland Crk Tr., vi.2008, G.R. Curler (4♂; ANSP)  . TRANSYLVANIA COUNTY, S Mill R @ US 276 & FS 1203, UV light trap, 12.vi.2008, J. Robinson (8♂). PA  : PERRY COUNTY, 4.5 km W Hwy 11–15, 34 km N Harrisburg, 5.v.1987, J.M. Cumming (1♂, 1♀, CNC)  . PHILADELPHIA COUNTY, Schuylkill Ctr for Env Ed , Trib Schuylkill R, 0.75 km SW of upper Roxborough Reservoir  , N40°03′15″ W75°15′00″, <100 m, UV light trap, along stream, 5–6.vi.1997, J.D. Weintraub (1♂, ANSP). SC: ANDERSON COUNTY, Pendleton, Tanglewood Spr   , N34°38′29.62″ W82°47′08.01″, 256 m, i.1988, J.C. Morse (5♂, CUAC). BARNWELL COUNTY, Savannah River Site, Lower Three Runs Crk , N33°18′24.80″ W81°31′09.70″, 7.iv.2007, JKM (2♂, 1♀, 11L)GoogleMaps  . CHESTER COUNTY, L Rocky Crk @ SSR 144, E of Cornwell , N34°36′58.50″ W81°08′13.52″, 23.v.2008, JKM (1L)GoogleMaps  . PICKENS COUNTY, Issaqueena Forest, Indian Crk, 19.iii.1989, C.R. Adler & P.H. Adler (13L); Same data, 15.vi.1989, C.R.Adler & P.H.Adler (1♂, 1♀) (reared with L & P exuviae). TN  : BLOUNT COUNTY, Lackey Crk @ Middle Settlement Rd , N35°47′22.42″ W84°02′37.39″, 256 m, 13.vi.2005, JKM & G.R. Curler (5♂, 2♀, 28L); Same data, 15.vii.2006, JKM (3♂, 1♀)GoogleMaps  . GSMNP, Tremont , 30.vi.2009, G.R. Curler (2♂, 1♀; ANSP)  . BRADLEY COUNTY, Red Clay SP, Blue Hole , N34°59′34.72″ W84°56′45.86″, 18.v.2013, JKM (1♀, 1L)GoogleMaps  . CLAIBORNE COUNTY, Cumberland Gap NHP, Gap Crk   , N36°36′05.00″ W83°40′05.39″, 413 m, 19–20.vii.2006, C. Parker & J. Robinson (3♂, USGS). COCKE COUNTY, GSMNP, Cosby Crk Nr. Park entrance, N35°46′31.84″ W83°12′46.70″, 547 m, 17.ix.2008, JKM (1♂, 1♀, 1P, 5L; ANSP). CUMBERLAND COUNTY, Sequatchie R, nr. Head of Sequatchie , N35°47′17.38″ W85°00′49.79″, 343 m, 3.v.2006, JKM (3L)GoogleMaps  . JEFFERSON COUNTY, Dumplin Crk @ Hebron Rd , N36°03′2.05″ W83°27′18.29″, 344 m, 26.v.2006, JKM (1♂); Same data, 16.vi.2008, JKM (2♀); Trib Piedmont Br @ Bays Mtn Rd, UV light trap, 9.viii.2006, JKM (1♂)GoogleMaps  . KNOX COUNTY, Powell Spr Br @ Bells Cmpgd Rd , N36°02′50.03″ W84°03′50.40″, 261 m, 18.vi.2006, JKM (5♂, 5♀); Same data, 08.vii.2015 (1♂)GoogleMaps  . LINCOLN COUNTY, Harmony Sprgs @ Rt 50, S of Lynchburg , N35°10′58.06″ W86°15′53.87″, 253 m, 11.iv.2011, JKM (2♂, 14L)GoogleMaps  . LOUDON COUNTY, Muddy Crk @ Muddy Crk Rd , N35°49′28.64″ W84°13′44.84″, 245 m, 3.vii.2007, JKM (4♂, 1♀)GoogleMaps  . MARION COUNTY, Daniel Cave Spr , N36.26° W85.48°, 8.ix.2010, JKM (4♂)GoogleMaps  . MORGAN COUNTY, Mammy ′s Crk , 10.v.2007, JKM (1♀). Frozen Head SP, Flat Frk Crk  , N36°07′27.60″ W84°30′30.80″, 416 m, 9.x.2013, JKM (13♂, 1♀, 1L); Judge Br, 2.x.2013 (7♂); Same data, 27.iv.2014 (1♂); Same data, 13.vi.2014 (7♂). SCOTT COUNTY, Stn Camp Ford Parking area , 17.v.2005, C.R. Parker (1♀, USGS)  . SEVIER COUNTY, Great Smoky Mtns NP, sm trib M Frk Little R nr. Elkmont CG, N35°39′39.50″ W83°34′58.44″, 661 m, 26.vii.2005, JKM (6♂, 3♀; ANSP); Trib Webb Crk @ Pittman Ctr , 27.v.2007, JKM (8♂, 6♀); LeConte Crk @ Twin Creeks, ex. Cherokee Orchard Rd, Malaise trap  , N35°41′14.97″ W83°29′56.41″, 603 m, 4.iv.–14.v.2003, C.R. Parker (12♂, 8♀, USGS); Twin Creek Science & Education Ctr , Malaise trap, 4.iv.2003, C.R. Parker (15♂, 9♀, USGS)  . VA: BEDFORD COUNTY, Abbott L outflow, UV light trap, N37°26′45.61″ W79°36′27.48″, 767 m, 8–9.vi.2006, C.R. Parker (3♂, USGS); Blue Ridge Parkway NP, Falling Rock Crk @ MP67.1, 17–18.vi.2007, C. Parker & J. Robinson (1♂, USGS)  . CARROLL COUNTY, Blue Ridge NP, Big Laurel Crk, MP 187.6, 7–8.vi.2006, C.R. Parker & J. Robinson (12♂, 3♀, USGS). FAIRFIELD COUNTY, Belleview to Difficult Run   , N38°56′47.04″ W77°10′55.82″, 69 m, iii. x.1915, W.L. McAtee (1♂, TAMU). FLOYD COUNTY, Blue Ridge Parkway NP, Mabry Mill @ MP176.1, UV light trap  , N36°44′56.72″ W80°24′17.69″, 877 m, 7–8.vi.2006, C. Parker (2♂, USGS). GILES COUNTY, Little Stoney Crk   , N37°21′ W80°36′, 646 m, 24.v.1990, G.W. Courtney (1♀, ISIC). GRAYSON COUNTY, Grayson Highlands SP, Big Wilson Crk, 13.vi.2004, B.J. Sinclair (1♂; CNC); Rivulet @ Meadow Beach Ln   , N36°37′11.52″ W81°02′57.36″, 784 m, 15.iii.2005, JKM (2L). PATRICK COUNTYGoogleMaps  , BRP NP, MP130.7, Mayberry Crk , UV light trap  , N36°42′20.10″ W80°26′32.39″, 860 m, 7–8.vi.2006, C. Parker (9♂, USGS). VT: RUTLAND COUNTY, Gifford Woods SP, along Kent Brook , 19.viii.1988, J.M. Cumming (1♂, 1♀, CNC)  .

Diagnosis. Males of this species can be distinguished from those of all other Nearctic dixids by the following characters: Morphological. In addition to the aforementioned characters diagnosing the species group, these characters separate males from those of D. elkmontensis  sp. nov. and D. vockerothi  sp. nov.: Basal gonocoxal lobe broadly squared apically; proximal lobe of subepandrial sclerite acute, with thin, strap-like connection to proctiger; apical lobe of subepandrial sclerite broad, subovoid, with apex directed dorsally. Molecular. Within the 66 nucleotides (22 codons) shown ( Fig. 35View FIGURE 35) an adenine at position 9 (vs. guanine) serves to distinguish this species from the other two. Within the encompassing amplified fragment of BZF, which is slightly over 1kb, D. ubiquita  sp. nov. is 4.5% divergent from D. elkmontensis  sp. nov. and 6.1% divergent from D. vockerothi  sp. nov. (JK Moulton, unpublished).

Description. Male. General coloration dark brown ( Figs 1, 2View FIGURES 1 – 5, 6View FIGURES 6 – 10). Wing ( Fig. 9View FIGURES 6 – 10) length (n =12) 3.2–4.1 (avg=3.6) mm. Head and its structures brown. Antenna ( Fig. 8View FIGURES 6 – 10) ca. 2/ 3X length of wing, clothed with whorls of short setae; pedicel small, collar-like; scape globose, ca. 4X width of flagellomere I. Flagellum with 14 articles. Flagellomere I cylindrical, 1.6X length of flagellomere II. Flagellomeres I and II most notably subcylindrical, with remaining flagellomeres increasingly shorter and cylindrical. Flagellomere XIV with pair of divergent apical setae. Maxillary palpus 4-segmented; ratio of segment lengths 1–4 = 1:3:5:6. Scutum ( Figs 1, 2View FIGURES 1 – 5) brown, lacking prominent stripes, with 4 rows of dark brown setae per side with a few additional setae interspersed, particularly anteriorly; midline raised, with adjacent lateral areas concave. Pronotal lobe brown, with 2 short and 1–2 long apical setae. Anepisternum and anepimeron brown, concolorous with head and scutum, bare. Katepisternum dark brown, with 3–5 setae medially. Katepimeron light brown, bare. Metepisternum and metepimeron light brown, bare. Laterotergite brown, bare. Legs brown. Pro- and mesothoracic legs symmetrical, with following segment length ratios [coxa, trochanter, femur, tibia, t1, t2, t3, t4, t5 (including claw)]: 2.5, 1, 15, 15, 11, 4.3, 2.5, 1, 2.5. Metathoracic legs differing in that t1 & t4 ca. 33% longer. Coxae light brown, with setae anterolaterally, those of metacoxa positioned more laterally. Foretibia not expanded apically. Fore- and mesotarsal claws pectinate, with 4– 5 prominent subapical tines, often with additional smaller tines. Metathoracic claw with 1 mesal and 1 basal much reduced secondary tines, sometimes with third one between them. Pro- and mesotibia not noticeably expanded apically. Metafemur expanded apically, with transverse row of ca. 12–15 uniformly sized setae on bulge. Tarsomeres 3 and 4, most noticeably of meso- and metathoracic legs, with variably thickened, sometimes hooked, proximal seta on ventral surface. Wing ( Fig. 9View FIGURES 6 – 10) light grayish brown, with weak infuscation at junction of Rs, R2+3, R4+5, and crossvein r-m, most noticeable when viewed from afar. Wing veins brown, setose. Rs arising near terminus of Sc. R2+3 arising proximal to crossvein r-m. Crossvein m-m weakened medially. False vein (FV) prominent, clearly distinct from and running parallel to CuA for most of its length. Halter brown, stem mostly brown, lighter on basal 1/5. Scutellum brown, with ca. 12 posteriorly directed transverse setae along posterior margin. Halter brown, stem mostly brown, lighter on basal 1/5. Abdomen mostly dark brown, with blue-green and purple iridescence, especially laterally ( Fig. 1View FIGURES 1 – 5). Basal fringe brown. Segments 2–6 with dark brown terga and grayish brown pleura. Segments 7–9 dark brown. Terminalia ( Figs 11–14View FIGURE 11View FIGURES 12 – 20): Tergite 9 (9T; epandrium) subtrapezoidal, with anterior margin convex. Epiproct well sclerotized, triangular. Sternite 9 (9S; hypandrium) subrectangular. Junction of epandrium and hypandrium distinct, clearly separated by membrane, in lateral view occurring at same plane as apex of ventral proctiger lobe. Cercus digitiform, slightly sinuous, with apex directed posterodorsally, its length (including base) 1.25X greater than lateral width of proctiger. Subepandrial sclerite bilobed ( Figs 11View FIGURE 11, 12View FIGURES 12 – 20), with proximal lobe acute, its articulation with venter of proctiger forming acute angle; distal lobe of SES broadly rounded apically, its ventral lip articulating with dorsal margin of parameres. Distal lobe of subepandrial sclerite appearing as narrow lip beneath proctiger in dorsal view. Gonocoxite subcylindrical, ca. twice as long as broad, with prominent basal and apical lobes. Basal gonocoxal lobe directed posterodorsally its dorsal margin slightly concave ( Figs 11View FIGURE 11, 14View FIGURES 12 – 20) with prominent setae on inner surface and spinules apically ( Figs 11View FIGURE 11, 12, 14View FIGURES 12 – 20), its squared apex ca. 1/2 as wide as gonocoxal midpoint depth and extended 0.125X beyond dorsal gonocoxal margin. Apical gonocoxal lobe ca. 1/ 3X length of gonostylus in lateral view ( Figs 11View FIGURE 11, 12View FIGURES 12 – 20), with prominent setae/ spines along posteroventral margin. Aedeagal guide ( Fig. 11View FIGURE 11) short, not extended beyond segment 9, broad, troughlike, curved anterodorsally from origin near aedeagus and basal gonocoxal lobe (claspette of authors) before continuing on posteriorly towards junction of parameres and ventral apodome of subepandrial sclerite. Ejaculatory duct short (following aedeagal guide), unsclerotized. Gonostylus falcate/lanceolate, 3.3–3.5X longer than greatest depth, clothed with anteriorly directed moderately developed setae, those on medial surface strongest; dorsal margin mostly smooth, with some wrinkles but not serrated; in ventral view apices twisted 90° medially ( Fig. 13View FIGURES 12 – 20). Aedeagus hastate, membranous, wrinkled, covered with spicules ( Fig. 14View FIGURES 12 – 20), positioned between parameres. Ventral plate deeply divided medially into quasi diamond-shaped halves.

Female. ( Figs 7, 10View FIGURES 6 – 10, 24–28View FIGURES 24 – 28). Similar to male except as follows: Body coloration ( Fig. 7View FIGURES 6 – 10) lighter overall, more reddish brown. Wing ( Fig. 10View FIGURES 6 – 10) length (n =10) 3.2–4.1 (avg=3.6) mm slightly darker overall. Antenna slightly more robust. Tarsal claws simple, or with at most single weak time medially. Thoracic pleura, including katepisternum, lighter brown, with 4–5 setae medially. Abdominal tergum light brown, with pinkish-purple sheen laterally. Terminalia ( Figs 24–26View FIGURES 24 – 28): 9T subrectangular. 9S strap-like, posterior margin distended medially. 10S divided into pair of thin triangular lobes, apices 2X width of proximal portion of structure before meeting medially. Cercus in lateral view hemi-ovoid, thickened and directed posterodorsally. In dorsal and ventral views lateral and medial margins of cercus convex and concave, respectively, and apices slightly convergent. Bursa copulatrix armed with two noticeable groups of 23–30 tooth-like spines of varying size ( Fig. 27View FIGURES 24 – 28). Spermatheca ( Fig. 28View FIGURES 24 – 28) golden brown, spherical, with weak surface sculpturing and short sclerotized neck at junction with bottlebrush-like duct.

Etymology. Named for the widespread distribution and range of habitats occupied by this species.

Distribution. Dixa ubiquita  sp. nov. is widespread in the southeastern Nearctic from the coastal plains of LA and SC throughout the Piedmont to high-elevation streams in the Appalachians. It is known to occur as far north as upstate NY ( Fig. 34View FIGURE 34).

Remarks. Dixa ubiquita  sp. nov. inhabits myriad stream types, usually those between 2–6 meters in width and ranging in flow from sluggish ( Fig. 29View FIGURES 29 – 33) to fast ( Fig. 30View FIGURES 29 – 33). It has been found in association with several species of Blepharicera Macquart  in many instances, including the type locality. It co-inhabits streams with several other dixid species, including fellow species group member D. vockerothi  sp. nov., as well as D. calciphala Moulton  , D. inextricata Dyar & Shannon  , D. modesta Johannsen, D.  sp. nr. repanda, D. terna Loew  , and Dixella indiana (Dyar)  . It is possible that, further north, this species and D. vockerothi  sp. nov. co-occur more frequently. A population of D. ubiquita  sp. nov. was sampled from a small tributary approximately 200 meters away from the type and only known locality of its sister species, D. elkmontensis  sp. nov. Adults of Dixa ubiquita  sp. nov. emerge by April in Great Smoky Mountains NP. In Louisiana and places of similar latitude it could possibly undergo continuous development.


Canadian National Collection of Insects, Arachnids, and Nematodes


Natal Museum


University of Minnesota Insect Collection


Cornell University Insect Collection


Academy of Natural Sciences of Philadelphia


Great Smoky Mountains National Park


Knox College


U.S. Geological Survey


Forest Research and Development Center and Nature Conservation


Southeastern Shanxi Teachers School














Dixa ubiquita

Moulton, John K. 2017

Dixa modesta

Peters 1966: 241
Johannsen 1903: 429