Dixa repanda Peters, 1966

Moulton, John K., 2018, Rediscovery of Dixa repanda Peters and description of its putative sister species, Dixa falcata sp. nov., from the south-central United States (Diptera: Dixidae), Zootaxa 4459 (1), pp. 171-178 : 175-177

Dixa repanda Peters

( Figs 4 , 6, 8, 10 )

Dixa repanda Peters in Peters & Cook, 1966: 249 .

Type material examined. HOLOTYPE ♂ (card pointed) labeled: “ Goodhue Co. [unty], Minn.[esota]/ May 21 1937 ”; “ D.G. Denning / Collector”. “ HOLOTYPE / Dixa / repanda / Peters/ USNM No. 67271 [red-trimmed label]” (USNM). Terminalia: Not examined, presumed lost.

Additional material examined. USA: Arkansas: STONE COUNTY, Ozark NF, Blanchard Sprs Crk below source [N35°57′31.4″ W92°10′43.1″, 166 m], 21.v.1991, B.J. Sinclair (1♂, CNC) . Iowa: JEFFERSON COUNTY, Black Bridge Spr, S of Waupeton , N42°39′44.2″ W90°52′55.7″, 195 m, 17.ix.2009, J.K. Moulton (13♂, 8♀) . Illinois: MONROE COUNTY, Bicklein Cave Spr, 8 km W of Waterloo, T2S R10W SE1/4SE1/4 Sec 19, Waterloo 7.5’ Quadrangle [N42°29′22.5″ W92°29′51.8″, 308 m], 14.xii.1996, J. Krejca et al (1♂, UWS) . Indiana: CRAWFORD COUNTY, Hoosier NF, Trickling str @ Hemlock Cliffs [N38°16′30.2″ W86°32′17.5″, 214 m], 19.v.1991, B.J. Sinclair (5♂, CNC) . PERRY COUNTY, Hoosier NF, Trib Middle Deer Crk @ CR10, N37°59′11.0″ W86°37′23.9″, 140 m, 4.x.2009, J.K. Moulton (2L*) . Kansas: RILEY COUNTY, Manhattan, “ Hibernating ” under rock [N39°10′13.1″ W96°39′01.7″], 13.xii.1930, H.L. Culer (1♂, USNM) . Missouri: PHELPS COUNTY, Meramac Spr, 12.9 km S St James [N37°57′12.8″ W91°31′57.8″, 261 m], 28.iv.1956, P.J. Spangler (1♂, USNM) . ST FRANCOIS COUNTY, St Francois SP, stream beside old schoolhouse, N37°59′21.6″ W90°30′49.7″, 238 m, 30.iv.2009, J.K. Moulton (2♂) . STONE COUNTY, Crane Crk @ Crane City Park , N36°54′08.2″ W93°34′25.0″, 339 m, 30.iv.2009, J.K. Moulton (1♀) . Oklahoma: JOHNSTON COUNTY, Viola Sprs @ McIntosh Rd , ex emergent vegetation, N34°22′46.5″ W96°31′36.5″, 241 m, 25.iii.2010, E.A. Bergey (1♂ & 3♀) . PONTOTOC COUNTY, unnamed spr ex D169 Rd, 4 km S of Fittstown , N34°34′22.7″ W96°38′51.0″, 313 m, 25.iii.2010, E.A. Bergey (1♂, 1♀) .

Diagnosis. The less strongly setose, curved, non-tapered, banana-like gonostylus coupled with obliterated cercus and larger, more protruding basal gonocoxal lobe distinguishes this species from all other Nearctic species, including D. falcata sp. nov.

Redescription. Differing from D. falcata sp. nov. as follows. Male. Wing length (n =10) 2.5–3.4 mm (avg=3.1). Terminalia ( Figs 4 , 6, 8, 10 ): Gonostylus slightly shorter, ca. 2.5X longer than greatest height, considerably less tapered apically and with shorter and sparser setae on medial surface. Basal gonocoxal lobe appearing more protrusive from dorsal gonocoxal margin in lateral view.

Female. Wing length (n =8) 2.7–3.7 mm (avg=3.3). Indistinguishable from those of D. falcata sp. nov. and several other similarly colored, related species.

Distribution and bionomics. Attempts by the author to collect material from near the type locality in Illinois (Havana) and paratype locality (environs of Rochester, MN) were unfruitful. Streams in and around Havana, IL, are heavily degraded and inaccessible due to co-opting for agricultural production. New collections of this species broadened its known range to the east to include southern portions of Indiana and Illinois and southwesterly into Arkansas, Missouri and Oklahoma ( Fig. 14). It likely also occurs in the Arkansas Ozarks as well as northern Kentucky. Dixa repanda appears to be multivoltine and likely typically overwinters as eggs, although one female examined taken near Manhattan, Kansas, was observed under a rock in mid-December. Larvae mature as early as March in the southern portion of the range. This species occurs in spring-fed streams ( Fig. 13 ) very similar to those preferred by D. falcata sp. nov., and they likely co-inhabit streams somewhere in the Ozark/Quachita region.

Remarks. Several issues hampered the author’s elucidation of the identity of this species. Firstly, the illustration of the male terminalia in Peters & Cook (1966, fig. 47) in lateral view does not accurately reflect the shape of the gonostylus. Secondly, the slide-mounted terminalia of the male holotype could not be located in the USNM and are presumed lost. Thirdly, the two paratype males could not be located and may also be lost. Lastly, attempts to collect streams in the environs of Havana, Illinois, the type locality, were fruitless as the streams were largely inaccessible and ones that were observed look extremely degraded. It was not until examining a male specimen taken near Manhattan, Kansas, that was identified as D. repanda by T.M. Peters, that the association between my material and the holotype was synched. The absence of any other Dixa species, besides the easily discernable D. fluvica Peters , taken in the study area also reinforces this decision.

Figures

FIGURES 3–4. Male terminalia, illustrated in lateral view. 3, D. falcata sp. nov. 4, D. repanda. Scale bar = 50 µm.

FIGURES 5–11. Male terminalia. 5–6, lateral view. 5, Dixa falcata sp. nov. 6, D. repanda. 7–8, ventral view. 7, Dixa falcata sp. nov. 8, D. repanda. 9–10, terminal view. 9, Dixa falcata sp. nov. 10, D. repanda. 11, D. falcata sp. nov., dorsal view. The red arrow in Fig. 11 denotes the reduced cercus. Scale bar = 50 µm.

FIGURES 12–13. Example habitats for D. falcata sp. nov. and D. repanda Peters. 12, Fowler Spring Branch, Powell, TN. 13, Black Bridge Spring, NNE of Balltown, IA.