Dixa inextricata Dyar & Shannon

Moulton, John K., 2016, The Dixa inextricata Dyar & Shannon (Diptera: Dixidae) species group, with two new cryptic species from the eastern Nearctic Region, Zootaxa 4121 (4), pp. 458-472: 467-468

publication ID

http://doi.org/10.11646/zootaxa.4121.4.6

publication LSID

lsid:zoobank.org:pub:F15F9CC4-A5CE-45D9-94F7-7C112AE71544

persistent identifier

http://treatment.plazi.org/id/03F37E07-6F47-410F-FF40-33C5FA1BFF2D

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Plazi

scientific name

Dixa inextricata Dyar & Shannon
status

 

Dixa inextricata Dyar & Shannon  

( Figs 11 View FIGURES 9 – 11 , 18–20 View FIGURES 12 – 20 , 22 View FIGURES 21 – 24 , 29–30 View FIGURES 25 – 30 )

Dixa inextricata Dyar & Shannon, 1924: 198   . Edwards, 1932: 12 (checklist); Cooper & Rapp, 1944: 250 (checklist); Nowell, 1963: 96 (catalog); Hubert, 1965: 101 (catalog; known distribution); Peters & Cook, 1966: 244 (re-description; lectotype designated); Peters, 1968: 2 (primary type information).

Type material. LECTOTYPE ( USNM Type No. 27452; Slide No. 2008) ♂, labeled: “[ USA: VIRGINIA]: [FAIRFIELD COUNTY]/ Dixa   / inextricata   D. & S./ Type / Dead Run, Va/ R.C. Shannon/ [Slide No.] 2008 ”; “ Type No. 27452 U.S. N.M. [red label]” ( USNM). PARALECTOTYPES: Same data as holotype, ♂ (Slide No. 2021); MARYLAND: [MONTGOMERY COUNTY], Plummers Island, 3 ♂ ( USNM Slide Nos. 2018, 2022, 2024). Cabin John, ♂, L. O. Jackson, ( USNM Slide No. 2017).

Additional material examined. CANADA: ONTARIO: Owen Sound, Inglis Falls Sprs, N 44 ° 31 ′ 33.15 ″ N W 80 ° 56 ′02.56″, 19.ii. 1986, B.J. Sinclair— 1 ♂; Same data, except 6.v. 1986 — 2 ♂. HALTON COUNTY, Rattlesnake Cons Area, nr. Buffalo Comp’d, N 43 ° 28 ′ 10.79 ″, W 79 ° 54 ′ 47.37 ″ W, 12.v. 1990, B.J. Sinclair (3 ♂, CNC). USA: GEORGIA: TOWNS COUNTY, Chattahoochee NF, Rt. 180 W of Spur to Brasstown Bald, 862 m, N 34 ° 50 ′ 39.40 ″ W 83 ° 47 ′ 55.20 ″, 15.iii. 2012, JKM— 7 ♂, 5 L; 27.iii. 2012 — 3 ♂, 8 L; 14.iv. 2012 — 17 ♂, 2 ♀, 1 P. WALKER COUNTY, Crockford-Pigeon Mtn WMA, Stream @ Keown Falls Trailhead ex Pocket Rd., N 34 ° 36 ′49.00″ W 85 °05′ 17.70 ″, 05.v. 2012, JKM— 1 ♂, 2 L. KENTUCKY: HARLAN COUNTY, Blanton Forest State Nature Preserve, Watt Crk, 430 m, N 36 ° 51 ′ 36.95 ″ W 83 ° 22 ′ 54.17 ″, 28.v. 2008, M.A. Floyd— 3 ♂. LETCHER COUNTY, Bad Branch, 566 m, N 37 °04′ 12.01 ″ W 82 ° 46 ′ 17.99 ″, 8.vi. 2007, JKM & M.A. Floyd— 5 ♂, 3 ♀. Lilly Cornett Woods, Big Everidge Crk, ex KY Rt 113, 345 m, N 37.0769 ° W 82.996 °, UV light trap, 23.vii. 2009, M.A. Floyd— 38 ♂, 11 ♀. WOLFE COUNTY, Red River Gorge Geological Area, small trib Red R nr Sheltowee Trace Trailhead, N 37 ° 49 ′ 37.53 ″ W 83 ° 37 ′ 26.73 ″, 9.vi. 2015, JKM— 15 ♂, 2 ♀. PENNSYLVANIA: ERIE COUNTY, Fourmile Crk, N 42 °08′ 15.71 ″ W 80 °00′ 35.85 ″, 1.vi. 1992, E.C. Mastellar (1 ♂, PSU). PHILADELPHIA COUNTY, Wissahickon Park, S of Livezeys Ln, Trib. 3 of Wissahickon Crk, 43 m, N 40 °02′09.02″ W 75 ° 12 ′01.25″, 20.x. 1998, J. Gelhaus (1 ♂, PAS). TENNESSEE: BLOUNT COUNTY, Small trickle @ Top of the World Dr, 24.iv. 2009, JKM— 1 ♂, 1 L. CUMBERLAND COUNTY, Potter’s Ford, wet rock face, UV light trap, 17–18.vi. 2007, C. Parker & J. Robinson (6 ♂, 6 ♀, USGS). FENTRESS COUNTY, Obed Wild and Scenic River NP, Staples Spr, N 36 °03′ 30.53 ″ W 84 ° 47 ′ 35.55 ″ W, 17.vi. 2007, J. Robinson— 6 ♂, 6 ♀. JEFFERSON COUNTY, Piedmont Branch @ Shield’s Ridge Rd, UV light trap, 9.viii. 2006, JKM— 1 ♀. VIRGINIA: CARROLL COUNTY, small crk nr. canoe rental ex. US Rt. 58, 10.ix. 2005, JKM— 1 ♂. FA I R FA X C O U N T Y, Dead Run, 14.iv. 1914, R.C. Shannon (1 ♂, USNM); 13.iii. 1915, R.C. Shannon (1 ♂, USNM); 18.iii. 1915, R.C. Shannon (1 ♂, USNM); 13.iv. 1925, R.C. Shannon (1 ♂, USNM). GRAYSON COUNTY, rivulet x-ing Meadow Beach Ln., ex CR 634, 783 m, N 36 ° 37 ′ 11.22 ″ W 81 °02′ 57.80 ″, 17.iii. 2005, JKM— 16 ♂, 1 ♀; 3.vii. 2006 — 1 ♂, 1 ♀; 17.viii. 2007 — 4 ♂, 2 ♀; 14.iv. 2012 — 2 P. PAGE COUNTY, Shenandoah NP, Big Meadows, 15.vi. 1941, A.L. Melander (1 ♂, USNM).

Diagnosis. This species can be distinguished from D. appalachiensis   sp. nov. and D. calciphila   sp. nov. by the following characters: Morphological. Gonostylus 2 X longer than its greatest depth when viewed laterally, with ventral margin nearly straight and apex not twisted medially; basal gonocoxal lobe subovoid, with posterior margin indented slightly and apex directed posteroventrally; cercus length half that of proctiger lateral width. Molecular. Among the most noticeable differences within the 66 nucleotides shown in Figure 38 View FIGURE 38 that serve to distinguish this species from the other two are amino acid substitutions at the following codon positions (shown as triplets): 16 (proline vs. serine) and 19 (lycine vs. arginine).

Re-description. Male. Same as D. appalachiensis   sp. nov., except as follows: Wing length (n = 11) 2.5–3.2 (avg= 2.8) mm. Male terminalia ( Figs 11 View FIGURES 9 – 11 , 18– 20 View FIGURES 12 – 20 ): Cercus length half that of proctiger lateral width. Basal gonocoxal lobe subovoid, distal margin indented, apex directed posterodorsally. Apical gonocoxal lobe ca. 1 / 3 X length of gonostylus. Gonostylus triangular in lateral view, 2 X longer than greatest depth/width, with apex straight, not twisted ca. 90 ° medially as seen in ventral view ( Fig. 19 View FIGURES 12 – 20 ), ventral margin straight or nearly so, posterior margin more uniformly serrate.

Female. Wing length (n = 5) 2.6 –3.0 (avg= 2.8) mm. Not reliably separated from D. appalachiensis   sp. nov. or D. calciphila   sp. nov.

Etymology. From the Latin prefix “ in -“ + Latin root “ extricat-“ meaning to release from an entanglement or difficulty.

Distribution. Dixa inextricata   is the most widely distributed of the three members of this newly recognized species group. It is confirmed from Ontario south through PA, VA and MD into northern GA within and immediately adjacent to the central Appalachian Highlands ( Fig. 37 View FIGURE 37 ). Specimens examined by Peters from upper NY are hypothesized to belong to this species although I was unable to observe them personally.

Remarks. Dixa inextricata   is found in and around small woodland streams ranging from spring seeps percolating through mud and leaf packs ( Fig. 35 View FIGURES 31 – 36 ) to larger and moderately flowing streams ( Fig. 36 View FIGURES 31 – 36 ) often having small riffles. It is sometimes associated with Dixa notata Loew   in highland trickles and with D. fusca   and D. terna Loew   in lowland trickles. In streams near the upper threshold of its size preference, it is often found with the ubiquitous D. modesta sensu Peters.   Adults are on the wing by mid-March in GA and VA. Records of specimens examined by Peters from upper NY are hypothesized to belong to this species based on suitable habitat. These specimens were not located in the USNM or the University of Minnesota collections.

Genetic evidence (J.K. Moulton, unpublished) shows some differentiation between populations in the Cumberland Plateau versus ones found in areas to the east. Known preimaginal habitats between these populations also differ in that the former are moderately flowing wider watercourses with riffles as opposed to tiny mostly mudbottomed ravine seepages. Armature of the bursa copulatrix in a specimen from Red River Gorge, KY ( Fig. 29 View FIGURES 25 – 30 ) possessed two groups of setae similar to what has previously been depicted for the species (e.g., fig. 64 in Peters & Cook 1966) but also a medial group of ca. 10 strong pegs. However, a Brasstown Bald, GA specimen ( Fig. 30 View FIGURES 25 – 30 ) possessed a medial group of ca. 40 + variably sized pegs.

USNM

Smithsonian Institution, National Museum of Natural History

CNC

Canadian National Collection of Insects, Arachnids, and Nematodes

PSU

Portland State University, Vertebrate Biology Museum

USGS

U.S. Geological Survey

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Order

Diptera

Family

Dixidae

Genus

Dixa

Loc

Dixa inextricata Dyar & Shannon

Moulton, John K. 2016
2016
Loc

Dixa inextricata

Peters 1968: 2
Peters 1966: 244
Hubert 1965: 101
Nowell 1963: 96
Cooper 1944: 250
Edwards 1932: 12
Dyar 1924: 198
1924