Dixa elkmontensis, 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 eastern Nearctic species, Zootaxa 4216 (3), pp. 247-260 : 254-255

publication ID

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

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scientific name

Dixa elkmontensis

sp. nov.

Dixa elkmontensis   sp. nov.

( Figs 15–17 View FIGURES 12 – 20 , 22 View FIGURES 21 – 23 )

Type material. HOLOTYPE, ♂ labeled: “ USA: TN: SEVIER COUNTY / Middle Frk. Little River /ds of Elkmont CG / N35°39′59.52″ W83°35′27.89″, 626 m / 26.vii.2005 / J.K. Moulton ”; “ HOLOTYPE / Dixa   / elkmontensis   / 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: TN: SEVIER COUNTY, Middle Frk. Little River , d/s of Elkmont CG, N35°39′59.52″ W83°35′27.89″, 626 m, 26.vii.2005, JKM (15♂, 2♀) GoogleMaps   ; Same data, 16.vii.2011 (7♂, 4♀, 1L); Same data, 15.vi.2012 (57♂, 13♀, 5L).

Diagnosis. This species can be distinguished from D. ubiquita   sp. nov. and D. vockerothi   sp. nov. by the following characters: Morphological. Basal gonocoxal lobe with apex subovoid, directed posterodorsally; proximal lobe of SES acute, with thin, strap-like connection to proctiger; apical lobe of SES broad, with apex directed ventrally. Molecular. Within the 66 nucleotides (22 codons) shown ( Fig. 35 View FIGURE 35 ) a thymine at position 26 (vs. adenine) and a thymine at position 38 (vs. cytosine) serve to distinguish this species from the other two. Within the encompassing amplified fragment of BZF, D. elkmontensis   sp. nov. is 4.5% divergent from D. ubiquita   sp. nov. and 9.1% divergent from D. vockerothi   sp. nov. (JK Moulton, unpublished).

Description. Male. Same as D. ubiquita   sp. nov., except as follows: Wing length (n =10) 3.4–4.1 (avg=3.7) mm. Terminalia ( Figs 15–17 View FIGURES 12 – 20 ): Apex of basal gonocoxal lobe narrower (ca. 1/3–2/ 5X depth of gonocoxite at midpoint in lateral view; Fig. 15 View FIGURES 12 – 20 ) and less squared.

Female. Wing length (n =10) 3.4–3.9 (avg=3.7) mm. Not reliably separated from D. ubiquita   sp. nov. or D. vockerothi   sp. nov.

Etymology. Named for the Elkmont area of Great Smoky Mountains National Park ( GSMNP), location of the type and only known locality.

Distribution. Known only from the upper reaches of Little River (East Prong) in the Elkmont region of GSMNP ( Fig. 34 View FIGURE 34 ).

Remarks. This species inhabits the widest lotic watercourse (10+m; Fig. 31 View FIGURES 29 – 33 ) of any known eastern Nearctic Dixa   species and is the only dixid found in this section of Little River. During warm summer evenings, individuals of this species, particularly males, are readily attracted to UV lights, likely the result of swarming behavior. Morphologically and molecularly, this species is more closely related to D. ubiquita   sp. nov. than to D. vockerothi   sp. nov. The shape of the basal gonocoxal lobe is intermediate to the character states observed in D. ubiquita   sp. nov. and D. vockerothi   sp. nov.


Canadian National Collection of Insects, Arachnids, and Nematodes


Southeastern Shanxi Teachers School


Forest Research and Development Center and Nature Conservation


Great Smoky Mountains National Park