A revision of the New World species of Gymnoclasiopa Hendel (Diptera, Ephydridae)

Abstract Species of the shore-fly genus Gymnoclasiopa Hendel from the New World are revised, including Gymnoclasiopa grecorum sp. n. (Alaska. Juneau: Gastineau Channel, Thane Road (S Juneau; 58°16.9'N, 134°22.4'W)) and Gymnoclasiopa matanuska sp. n. (Alaska. Matanuska-Susitna: Palmer (Matanuska River; 61°36.5'N, 149°04.1'W)). We also clarify the status of previously described species, including those now discovered to have Holarctic distributions and/or for which sexual dimorphism was not appreciated and the species was described twice, including Gymnoclasiopa montana (Cresson) as a syn. n. of Gymnoclasiopa bohemanni (Becker). Two species, Gymnoclasiopa bella (Mathis), comb. n., and Gymnoclasiopa chiapas (Mathis), comb. n., are transferred from Ditrichophora to Gymnoclasiopa, and Gymnoclasiopa cana Cresson stat. rev. and Ditrichophora canifrons Cresson, stat. rev. are returned to Ditrichophora, the genus in which Cresson originally described them. A neotype is designated for Gymnoclasiopa tacoma to stabilize the nomenclature of this species. The two excluded species, Ditrichophora cana and Ditrichophora canifrons, are diagnosed and distributional data are also provided. For all known New World species of Gymnoclasiopa, structures of the male terminalia are described for the first time and are fully illustrated. Detailed locality data and distribution maps are also included. To provide context and also to facilitate identification, diagnoses are included for the tribe Discocerinini and genus in addition to a key to the genera and species occurring in the New World.


Introduction
The shore-fly genus Gymnoclasiopa Hendel occurs primarily in the Holarctic Region  with some species being found jointly in both the Nearctic and Palearctic Regions. Discovering additional species common to both biogeographic regions is an objective of this study, as is unraveling any nomenclatural issues that may result when the same species was described separately in both biogeographic regions. Another impetus for this revision is to contribute to ongoing studies of the Alaskan and Mongolian faunas, among others, for which correctly determined species are essential. This revision treats congeners occurring in the New World.
Although specimens are not generally uncommon in nature, most collections, with few exceptions, have relatively few specimens, and the genus is not generally well known except to specialists. Only a few authors have reported on any included species, and aside from , there are no comprehensive treatments available. The literature on included taxa is not extensive and mostly comprises alpha-level taxonomic treatments, frequently as isolated species descriptions. In view of recent field work and discoveries, the available literature is also inadequate for dealing with species that are found in both the Nearctic and Neotropical Regions. Likewise, the obvious sexual dimorphism that is now recognized in some species was not then appreciated, which contributed to confused concepts of some species and thus to incorrect determinations. We also know virtually nothing about the ecology and natural history of any of the included species except for brief habitat characterizations where adults have been found (Deonier 1965). With clarification of species--how they can be recognized and where they occur--we hope that additional research on immature stages and other aspects of their natural history and ecology will be fostered and facilitated.  provided a brief synopsis of Nearctic species. The included species, however, were treated within the genus Ditrichophora, which was and continued to be their accepted status until Zatwarnicki (1992) and Mathis and Zatwarnicki (1995) accorded generic status to Gymnoclasiopa based on characters of the male terminalia. Determining generic concepts continues to be a difficult issue because external characters, which were used exclusively in the original diagnosis of the genus, are not always wholly concordant with interpretations of structures of the male terminalia.

Methods and materials
The descriptive terminology, with the exceptions noted in Mathis (1986) and Mathis and Zatwarnicki (1990a), follows McAlpine (1981). Because specimens are small, usually less than 3.5 mm in length, study and illustration of the male terminalia required use of a compound microscope. We have followed the terminology for most structures of the male terminalia that other workers in Ephydridae have used (references in Mathis 1986;Zatwarnicki 1990a, 1990b), such as surstylus. Zatwarnicki (1996) suggested that the pre-and postsurstylus correspond with the pre-and post-gonostylus and that the subepandrial sclerite is the same as the medandrium. The terminology for structures of the male terminalia is provided directly on Figs 1-3. We use the term basal flagellomere for the large antennomere beyond the pedicel. We prefer this term over "first flagellomere" as there may be more than one flagellomere involved, and basal does not imply a number or numbers. We likewise do not use "postpedicel" (Stuckenberg 1999) for this antennomere because at least the multisegmented arista is beyond the pedicel in addition to the large antennomere, and postpedicel is thus ambiguous and lacking in precision.
Dissections of male terminalia were performed following Clausen and Cook (1971) and Grimaldi (1987). Abdomens were removed with microforceps and macerated in a sodium hydroxide solution. Cleared genitalia were then transferred to glycerin for observation, description, and illustration. The dissected abdomen was placed in a plastic microvial filled with glycerin and attached to the pin supporting the remainder of the insect from which it was removed.
The species descriptions are composite and not based solely on holotypes. Head and two venational ratios used in the descriptions are based on three specimens (largest, smallest, and one other): gena-to-eye ratio -genal height (immediately below maximum eye height)/eye height; costal vein ratio -the straight line distance between the apices of R 2+3 and R 4+5 /distance between the apices of R 1 and R 2+3 ; M vein ratio -the straight line distance along vein M between crossveins dm-cu and r-m/distance apicad of dm-cu.
Distribution maps were made using ESRI ArcView© GIS 3.2. Longitude and latitude coordinates were obtained for the locality where each specimen was collected and entered into a Microsoft Excel© spreadsheet. If unavailable directly from specimen labels, longitude and latitude were estimated using gazetteers and maps to determine the geographical coordinates. Localities of specimens were plotted on a world land projection, presented within ESRI ArcView layouts and exported as encapsulated postscript (EPS) files.
Many specimens examined for this study are in the National Museum of Natural History, Smithsonian Institution, Washington, D.C. (USNM). We also borrowed and studied numerous specimens, especially primary types from the following museums: ventral margin with lobate appendix providing attachment for genital muscles that move aedeagus, sometimes fused with base of aedeagus; gonites paired, connecting sides of base of aedeagus and laterodorsal margin of epandrium, bearing 1 or some setulae; subepandrial plate reduced; aedeagus tubular, tapered anteriorly; ejaculatory apodeme usually lacking, if present as a spatula against background of ductus ejaculatorius.
Discussion. Starting with Cresson (1925), who first described Discocerinini, and including all students of the family until Mathis and Zuyin (1989), the diagnoses, descriptions, and catalogs of this tribe included some taxa that are not closely related phylogenetically, rendering the tribe polyphyletic. Mathis and Zuyin (1989) recharacterized Discocerinini using synapomorphies and resulting in a monophyletic tribe into which Mathis and Zatwarnicki (1995) included eight genera and 143 species in their world catalog. Zatwarnicki and Mathis (2001) added two additional genera, Galaterina and Orasiopa, and altered the status of some subgenera in their phylogenetic study of the tribe.

Diagnosis.
Gymnoclasiopa is distinguished from other genera of the tribe Discocerinini by the following combination of characters: Small to moderately small shore flies, body length 1.70-3.30 mm; generally mostly bare to sparsely microtomentose, shiny to subshiny species. Head: Frons lacking orbital seta. Face moderately prominent at level of dorsal facial seta; antennal grooves generally weakly defined ventrally; face lacking secondary series of setae; facial setae 2-3, dorsal setae not arising from shiny papilla, lacking a dorsoclinate seta at lower lateral extremity; parafacial narrow throughout length, lacking setulae; gena generally low to moderate. Eye generally oval to nearly round, moderately conspicuously microsetulose, bearing interfacetal setulae not discernible by light stereomicroscope. Thorax: Presutural supra-alar seta well developed; postsutural supraalar setae lacking; acrostichal setae present; notopleuron bare of setulae. Wings transparent, rarely infuscate apically; costa bearing 3-4 long, dorsal setae between humeral and subcostal breaks. Forefemur normally developed, lacking row of short, stout setae along posteroventral surface; hindtibia lacking a preapical, ventral, spurlike seta. Abdomen: Tergites usually unicolorous, lacking light colored areas laterally. Tergite 4 of ♂ as long or slightly than tergite 3. Male terminalia: Epandrium U-shaped in dorsal view, complete posteriorly; arms projected ventrad, posterior surface generally setulose, generally thickly formed, especially dorsal portion, arms tapered gradually toward ventral apex; cercus not fused anteriorly with epandrium, in posterior view broadly lunate, or elongate (3× longer than wide), posterior apex more narrowly pointed; pregonite variously shaped, but generally rounded apically, bearing 2-5 setulae along basoposterior margin, and 1 subapical setula along ventral margin toward hypandrium, in lateral view fusiform, in dorsal view ovate with lunate fold on 2/3 ventral margin overlapping the sides of aedeagus; postgonite more or less regularly lobate, in lateral view rod-shaped, slightly widen dorsally, ventrally it is associated with hypandrium arm, and dorsally with posteroventral margin of post-gonite; aedeagus longer than wide, mostly tubular, in dorsal view navicular, broadly rounded or bifurcate apically, bearing lateromedial projections attached to posterior margin of pregonites, in lateral view cigar shaped or ovate, or tapered toward apex; phallapodeme separate from aedeagus, in dorsal view elongate, bifurcated basally and broadly clavate at the apex; keel in lateral view variously shaped, more or less triangular or sometimes hemispherical with posterior margin curved; hypandrium in dorsal view trapezoidal, broadly rounded along anterior margin, posterolateral arms broad, posterior incision reach to 1/3 hypandrial length, in lateral view flat, sometimes irregularly, but slightly curved; ejaculatory apodeme present in form of patella, in lateral view L-shaped. Distribution. Holarctic and Neotropical Region. Natural history. Adults are found on bare, sandy to muddy shorelines of both lentic and lotic aquatic systems in primarily temperate climates. Although we have not quantified our collecting, our perception is that specimens are more common in lotic systems. Nothing is known about the immature stages, and little else is known about most other biological aspects of the included species (Zack 1983). Diagnosis. This species is distinguished from congeners by the following combination of characters: Moderately small to medium-sized shore flies, body length 2.10-3.25 mm; generally shiny black. Head: Frons blackish, moderately microtomentose gray; mesofrons narrowly triangular. Antenna black, basal flagellomere covered with silver microtomentum; arista with 4-6 dorsally branching rays. Face relatively flat with antennal grooves mostly inconspicuous, very shallow; facial microtomentum silvery white, sericeous; gena moderately high, genal height subequal to height of basal flagellomere; gena-to-eye ratio 0.12-0.20. Maxillary palpus black. Thorax: Generally subshiny to mostly shiny, only very sparsely microtomentose dorsally. Wing hyaline; costal vein ratio 0.34-0.40; M vein ratio 0.58-0.60; halter stem blackish brown; knob yellowish to whitish. Coxae, femora, and tibiae black, midtibia with some grayish microtomentum from some angles; male forebasitarsomere black; female forebasitarsomere at least yellowish basally, becoming darker apically; basal tarsomeres of mid-and hindtarsi yellow, contrasted distinctly with black male forebasitarsomere. Abdomen: Dorsum generally subshiny to mostly shiny, with only sparse microtomentum dorsally. Male terminalia : Epandrium in posterior view (Fig. 1) as a broadly rounded, inverted U, width of dorsal portion slightly narrower than lateral arms, lateral arms shallowly arched, in lateral view wider ventrally; cercus in posterior view (Fig 1) semilunate, narrower dorsally than ventrally; aedeagus in lateral view (Figs 3,12) slipper-like, base deeply and unevenly incised, posterior arm of folded over at right angle, tapered toward apex, apex moderately narrowly rounded, in ventral view (Figs 2, 6) expanded laterally from narrow base to wider apex, apical margin bilobed, narrowly incised medially, each lateral lobe as wide as aedeagal base, with thin, wing-like, narrow projections sub-basally; phallapodeme in lateral view (Figs 3,9) more or less triangular, in ventral view (Figs 2,8) longer than wide, bar-like with basal, sub-basal and apical crossbars, apical margin shallowly emarginate; ejaculatory apodeme in lateral view (Figs 3, 11) L-shaped, in ventral view (Figs 2, 7) peanut-like; postgonite in lateral view (Figs 3,13) acutely pointed basally, thereafter becoming wider then apex narrowed, digitiform, bearing 2-3 setulae along basoposterior margin and 1 setula along margin toward hypandrium; pregonite in lateral view (Figs 3-4) moderately elongate, tapered, narrowed toward hypandrium, expanded toward aedeagus, aedeagal end truncate; hypandrium in ventral view (Figs 2,14) wide, width nearly twice length, broadly and shallowly rounded along anterior margin with anterolateral, pointed, lateral projections, shallowly emarginate along posterior margin medially, in lateral view (Figs 3,15) arched, posterior angle acute, thereafter anteriorly becoming wider, widest before anterior margin.   -13 Sep, 1908-13 Sep, , 1909-13 Sep, ,1912-13 Sep, , 1923-13 Sep, , 1965-13 Sep, , 1970-13 Sep, , 1971 Remarks. Among Nearctic species, this is by far the most abundant and commonly collected, and is found throughout the West (Fig 16). This is also one of the more easily recognized species, making it unlikely to be confused with congeners. It is distinguished by the entirely black antennae and forelegs and the subshiny to shiny mesonotum and abdomen. Diagnosis. This species is distinguished from congeners by the following combination of characters: Small to medium-sized shore flies, body length 1.90-3.10 mm; generally shiny black. Head: Frons of male generally moderately microtomentose to anterior margin, only small, linear patch anterolaterally and at base of setae bare of microtomentum; frons of female with small bare areas anteriorly; 1 proclinate, frontoorbital seta, inserted just behind and laterad of reclinate seta. Antenna black; apical margin of pedicel and 1st flagellomere invested with whitish gray microtomentum; arista bearing 5 dorsal rays. Face bearing 2 lateral, facial setae, dorsal seta inserted at level of facial prominence, ventral seta inserted toward ventral margin, distance between facial setae about equal to length of basal flagellomere; face black but mostly invested with silvery white microtomentum, only ventral portion of antennal grooves, vertical stripe immediately adjacent to parafacial, and medial stripe that curves laterally ventrally bare, shiny, black; parafacial completely microtomentose, whitish gray; gena moderately short; gena-to-eye ratio 0.10-0.13. Mouthparts, including maxillary palpus, black. Thorax: Mesonotum generally sparsely microtomentose, golden brown, becoming sparser to bare laterally, through supra-alar area, thereafter laterally sparsely microtomentose, male bearing a very distinctive stripe of dense, fine, brown microtomentum extended from postpronotum through most of notopleuron, female shiny black, similar to adjacent areas; prescutellar acrostichal setae weakly developed. Wing hyaline; costal ratio 0.37-0.44; M vein ratio 0.60-0.63; halter stem blackish brown; knob yellowish to whitish yellow. Legs except tarsi black, mostly shiny, femora with some surfaces very sparsely microtomentose; tarsi yellow except apical 2 brown; forefemur unadorned with short, peglike setulae along posteroventral surface. Halter white. Abdomen: Black, generally shiny, especially laterally and ventrally. Male terminalia : Epandrium in posterior view (Fig 17) as a broadly rounded, inverted U, dorsal portion slightly narrower than lateral arms, in lateral view wider ventrally; cercus semilunate in posterior view (Fig 17); aedeagus in lateral view (Fig 19) slipper-like, base deeply and unevenly incised, tapered toward apex, apex moderately narrowly rounded, in ventral view (Fig 18) narrowly thumb-like with basal third tapered, basal margin narrowly truncate, apical 2/3 nearly parallel-sided, apex moderately widely rounded, with thin, wing-like, narrow projections sub-basally; phallapodeme in lateral view (Fig 19) more or less triangular, in ventral view (Fig 18) as an inverted T; ejaculatory apodeme in lateral view (Fig 19) L-shaped; postgonite in lateral view ( Fig  19) acutely narrow basally, thereafter becoming wider than apex narrowed, digitiform, bearing 2-3 setulae along basoposterior margin and 1 setula along margin toward hypandrium; pregonite in lateral view (Fig 19) moderately elongate, tapered, narrowed toward hypandrium, expanded toward aedeagus, aedeagal end truncate; hypandrium in ventral view (Fig 18) wide, width nearly twice length, broadly and shallowly rounded along anterior margin with anterolateral, pointed, lateral projections, deeply incised along posterior margin medially, in lateral view (Fig 19) arched, posterior angle acute, thereafter anteriorly becoming wider, widest before anterior margin.  Distribution (Fig 20). Neotropical: Mexico (Chiapas), West Indies (Dominican Republic, Jamaica).

Key to species of Gymnoclasiopa from the New World
Remarks. All specimens were collected in montane habitats that are frequently overcast if not enshrouded in a foggy mist. The specimens from the Dominican Republic were mostly collected from a pile of spoiling cabbage that had been discarded along the roadside.
This species is sexually dimorphic with males having a brown stripe of dense but fine microtomentum extended from the postpronotum to the posterior margin of the notopleuron. Females are shiny black throughout this area of the thorax, similar to portions of the mesonotum that are immediately adjacent.
Based on external characters, this species was placed initially in the genus Ditrichophora, but structures of the male terminalia indicate a closer association with Gymnoclasiopa. This species is distinguished from congeners, especially G. chiapas, by the following combination of characters: Postpronotum and most of notopleuron of male densely invested with fine, brown microtomentum, contrasted sharply with generally shiny, adjacent mesonotum and anepisternum; prescutellar acrostichal setae weakly developed; frons of male generally sparsely microtomentose to anterior margin; halter white; only 1 proclinate fronto-orbital seta; and pattern of silvery white microtomentum on face (see species description). ( Diagnosis. This species is distinguished from congeners by the following combination of characters: Small to medium-sized shore flies, body length 1.80-3.35 mm; head and thorax generally microtomentose gray, abdomen subshiny to shiny black. Head: Frons densely but finely microtomentose. Antenna yellowish, sometimes basal flagellomere slightly darkened dorsally; arista bearing 5 dorsal rays. Face relatively flat with antennal grooves inconspicuous; facial microtomentum generally sericeous, bright yellow (males) or grayish yellow (females, grayer in antennal grooves); gena moderately high, gena-to-eye ratio 0.14-0.18. Maxillary palpus yellow to yellowish red. Thorax: Anterolateral area of mesonotum, just mediad of area from postpronotum through notopleuron, densely microtomentose, mostly dull; lateral mesonotal area from and including postpronotum and notopleuron, densely and finely microtomentose; this area of males brown, contrasted with whitish to silvery gray microtomentum of broad, medial portion; same area in female concolorous with medial coloration. Wing of hyaline, not darkened along anterior region; costal ratio 0.0.39-0.50; M vein ratio 0.50-0.59; halter stem yellowish tan, knob yellowish white to white. Forecoxa yellow ventrally; foretibia mostly yellow, sometimes slightly brownish to grayish medially; midtibia mostly yellow to mostly grayish with only apices yellow, but with brownish area around apical 1/3; hindtibia without ventroapical spur, mostly grayish except for apices. Abdomen: Tergites 1-4 sparsely and finely microtomentose medially, subshiny; lateral margins of tergites and tergite 5 shiny black with microtomentum either lacking or sparse. Male terminalia (Figs 21-23): Epandrium in posterior view (Fig 21) as a broadly formed, inverted U with the base more narrowly formed, dorsal portion more thinly developed than lateral arms, lateral arms widespread ventrally, shallowly arched, enlarged ventrally, broadly rounded, setulae more clustered at ventral margin; cercus in posterior view (Fig 21) elongate, irregularly lunate, dorsal apex very narrow, digitiform, expanded toward ventral apex, ventral apex rounded, both lateral and medial margins arched, setulae more clustered at ventral margin; aedeagus in lateral view (Fig  23) slipper-like, base shallowly emarginate, tapered very gradually toward apex, apical half nearly parallel sided, apex bluntly rounded, in ventral view (Fig 22) elongate, expanded laterally from narrow base on basal 1/4, thereafter to apex almost parallel sided, apical margin rounded with tiny notch medially; phallapodeme in lateral view (Fig 23) more or less irregularly triangular, extension toward hypandrium more elongate than angle towards aedeagal base, in ventral view (Fig 22) I-shaped, subapical crossbar shorter and basal crossbar, with tapered shoulders, basal crossbar wider, widely Y-shaped, apical margin very shallowly emarginate; ejaculatory apodeme in lateral view robustly comma-shaped, in ventral view obtusely L-shaped; postgonite in lateral view (Fig 23) with basal half robust, thereafter abruptly tapered to a narrow, slightly tapered, digitiform process, posterior margin with a few setulae, extended process with a single, longer setula, in ventral view (Fig 22) as an elongate isosceles triangle, tapered gradually toward apex, width of base about half length, angles rounded, lateral and medial margins nearly straight; pregonite in lateral view (Fig 23) moderately elongate, triangular, width at base almost twice lengths of sides, in ventral view (Fig 22) lunate with apices pointed; hypandrium in ventral view (Fig 22) robustly V to U-shaped, lateral margins slightly expanded posteriorly, anterior margin very broadly rounded, posterior margin conspicuously emarginate, widely U-shaped, in lateral view (Fig 23) Mathis & Zatwarnicki NRS [red]." The lectotype female is double mounted, is in good condition (anterior margin of right wing slightly broken near middle), and is deposited in the NRS. When Becker (1896; 159) described this species he noted that "diese neue Art fand ich in Bohemann's Sammlung."

Gymnoclasiopa bohemanni
The Remarks. This species, like many but not all congeners, is sexually dimorphic, especially the coloration of the face and the mesonotal area from the postpronotum to the base of the wing as noted in the diagnosis. These differences, which were not always recognized, probably was a major factor contributing to this species being described more than once.
This species is similar to G. pulchella in having yellowish antennae, maxillary palpi, and foretibiae (sometimes brownish apically) but is distinguished from that species as follows (also see key): The anterolateral area of the mesonotum, just mediad of the area from the postpronotum through the notopleuron is densely microtomentose, mostly dull; the lateral mesonotal area from and including the postpronotum and the notopleuron is densely and finely microtomentose (this area in males is brown and is contrasted with whitish to silvery gray microtomentum of the broad, medial portion; the same area in females is concolorous with the medial coloration). ( Diagnosis. This species is distinguished from congeners by the following combination of characters: Moderately small shore flies, body length 2.00-2.65 mm; generally shiny black. Head: Frons of male and female similar, moderately microtomentose on posterior portion, although bare at bases of setulae and small area just laterad of posterior ocelli, anterior third of frons bare, shiny, with 2 lunate indentations, medial area with pointed extension of moderately microtomentum from posterior portion; 1 proclinate, fronto-orbital seta, inserted just behind and laterad of reclinate seta. Antenna black; apical margin of pedicel and basal flagellomere invested with whitish gray microtomentum; arista bearing 5 dorsal rays. Face bearing 3 lateral, facial setae, dorsal seta longest, inserted at level of facial prominence, ventral setae progressively shorter, evenly spaced with distance between less than width of 1st flagellomere; face mostly black, shiny, but with pattern of silvery white microtomentose, vertical stripes; lateral facial stripe immediately adjacent to parafacial, other vertical stripe just laterad of midfacial vertical bare area; also silvery white microtomentose on dorsal portion of antennal grooves and along ventral, facial margin; parafacial bare, shiny black; gena-to-eye ratio 0.10-0.12. Mouthparts, including maxillary palpus, black. Thorax: Mesonotum generally sparsely microtomentose, golden brown, becoming bare laterally through supra-alar area and continuing ventral through pleural area; prescutellar acrostichal setae well developed. Wing hyaline; costal ratio 0.40-0.43; M vein ratio 0.70-0.73; halter stem blackish brown; knob yellowish to whitish. Legs except tarsi black, mostly shiny, femora with some surfaces very sparsely microtomentose; tarsi yellow except apical 1-2 brown; forefemur with row of numerous, very short, peglike setulae along posteroventral surface. Abdomen: Tergites black, generally shiny, especially laterally and ventrally. Male terminalia (Figs 25-27): Epandrium in posterior view (Fig 25) moderately broadly as an inverted, robust U, dorsal portion nearly straight, narrower than lateral arms, ventral margins of arms slightly expanded, broadly rounded, in lateral view wider ventrally; cercus in posterior view (Fig 25) semilunate, elongate, narrow, shallowly arched, parallel sided; aedeagus in lateral view (Fig 27) slipper-like, base deeply and unevenly incised, tapered toward apex, apex moderately narrowly rounded, in ventral view (Fig 26) broadly tapered on basal third, basal margin almost truncate, very shallowly arched, with thin, wing-like, narrow projections sub-basally, apical margin twice as broad as basal margin, shallowly crenulate; phallapodeme in lateral view (Fig 27) more or less triangular, in ventral view (Fig 26) as an inverted T; ejaculatory apodeme in lateral view (Fig 27) obtusely L-shaped, tapered from wider apex to narrow base; postgonite in lateral view (Fig 27) as a parallelogram, acutely narrow basally and apically, each lateral margin obtusely angulate, bearing 2 setulae along basoposterior margin and 1 setula along margin toward hypandrium; pregonite in lateral view (Fig 27) moderately elongate, tapered, narrowed toward hypandrium, flared toward aedeagus, aedeagal end truncate, in ventral view shallowly arched medially, thereafter laterally slightly tapered, lateral margin rounded; hypandrium in ventral view (Fig 26) broadly and shallowly rounded along anterior margin, in lateral view (Fig 27) arched, posterior portion digitiform, thereafter anteriorly becoming wider, dish-like. Type locality. Mexico. Chiapas. Biosfera El Triunfo (ca 49 km S Jaltenango; 15°39.5 'N, 92°48.5'W; 1800 m).

Remarks.
El Triunfo is a site in the cloud forest of southern Mexico (some of the only cloud forest that remains largely undisturbed in Mexico).
Based on external characters, this species was placed initially in the genus Ditrichophora, but structures of the male terminalia indicate a closer association with Gymnoclasiopa. This species is distinguished from congeners, especially D. bella, by the following combination of characters: Postpronotum and notopleuron of males are generally bare of microtomentum and shiny, similar to the mesonotum and anepisternum; the prescutellar acrostichal setae are well developed; males have the anterior third of the frons bare of microtomentum, shiny black; halteres are white; there is only one proclinate fronto-orbital seta; and by the pattern of silvery white microtomentum on face (see species description).

Gymnoclasiopa matanuska
Etymology. The species epithet, matanuska, refers to the glacier, river, and valley in southcentral Alaska where many specimens of the type series were collected along lotic aquatic systems. The name is apparently of Athabaskan origin and means a strong, gusty, northeast wind, which occasionally occurs in this region during the winter. The name is a noun in apposition.
Remarks. Like a number of shore-fly species with Holarctic distributions, including G. matanuska, the Bering Strait is apparently a conduit between the Old and New Worlds.
Although similar to other congeners, especially G. grecorum, this species is distinguished by the black maxillary palpus and basitarsomere of the foreleg, the densely microtomentose gray to tannish gray body, especially on the thorax and abdomen, and the high genal height.
Diagnosis. This species is distinguished from congeners by the following combination of characters: Small to moderately small shore flies, body length 1.  (Fig 41) as a moderately rounded, inverted U with the base more narrowly formed, width of dorsal portion slightly narrower than lateral arms, lateral arms shallowly arched, setulae more clustered at ventral margin; cercus in posterior view (Fig 41) elongate, evenly oval, dorsal margin very slightly more narrowly rounded than ventral margin, setulae more clustered at ventral margin; aedeagus in lateral view (Fig 43) slipper-like, base shallowly emarginate, tapered gradually toward apex, apex moderately broadly rounded, in ventral view (Fig 42) expanded laterally from narrow base on basal 1/3, thereafter to apex almost parallel sided, apical margin moderately deeply incised medially, bilobed; phallapodeme in lateral view (Fig 43) more or less irregularly triangular, extension toward hypandrium more elongate than angle towards aedeagal base, in ventral view (Fig 42) I-shaped, apical crossbar robust, wider than basal crossbar, apical margin very shallowly emarginate; ejaculatory apodeme in lateral view robustly comma-shaped, in ventral view L-shaped; postgonite in lateral view (Fig 43) robustly bar-like, basal 1/3 angulate, narrower than extended, mostly parallel-sided apical 2/3, bearing 3-4 setulae along posterior margin and 2 setulae subapically along anterior margin, in ventral view (Fig 42) as an elongate triangle, wide basally, tapered to narrowly rounded apex; pregonite in lateral view (Fig 43) moderately elongate, straight, clavate, wider apically than narrow base, in ventral view (Fig 42) robustly J-shaped with pointed, curved base and expanded apex; hypandrium in ventral view (Fig 42) almost quadrate, as wide as long, anterior margin shallowly curved, lateral margins curvey, posterior margin broadly and moderately deeply emarginate, forming wide pocket, in lateral view (Fig 43) Cresson, Jr. [maroon; species name handwritten]." The holotype is directly pinned, is in good condition (thorax partially broken where pin is inserted), and is deposited in the MCZ (31758). Cresson (1924: 160)  UNITED STATES. ALASKA. Fairbanks North Star: Fairbanks, Lake Ballaine (64°52.2'N, 147°49.5'W;160 m), 2 Aug 2011, D. and W. N. Mathis (1♂, 3♀;Gymnoclasiopa pulchella. Mathis and Zatwarnicki 1995: 178 [generic combination;world catalog]. Clasiopa fulgida Becker 1896: 156. Becker 1902. Diagnosis. This species is distinguished from congeners by the following combination of characters: Small to moderately small shore flies, body length 1.60-2.45 mm; generally coloration of males and females sexually dimorphic to a degree with females generally less microtomentose. Head: Frons of male densely microtomentose, moderately intensely whitish gray to white, that of female moderately microtomentose, whitish gray microtomentose anterior, becoming less microtomentose, more blackish posteriorly; proclinate fronto-orbital seta 1. Antenna generally yellowish orange (sometimes apex of basal flagellomere and scape darkened); arista bearing 4-6 dorsal rays. Face relatively flat; antennal grooves, especially ventral margins, inconspicuous; face of male densely microtomentose, intensely yellow, that of female less densely microtomentose, silvery white; facial setae inserted close to parafacials, aligned vertically; gena very short, genato-eye ratio 0.065-0.072. Maxillary palpus yellowish orange. Thorax: Anterolateral area of mesonotum, just mediad of area from postpronotum through notopleuron, thinly to very thinly microtomentose, subshiny to shiny with some metallic luster; lateral mesonotal area from and including postpronotum and notopleuron in males with thin microtomentum whitish to grayish, similar to central mesonotal microtomentum, not brown; mesonotum of female more thinly microtomentose, appearing blackish with whitish gray microtomentum more sparse; pleural areas generally shiny black with some very thin microtomentum ventrally. Wing mostly hyaline; costal section II conspicuously longer than costal section III by about twice length; costal vein ratio 0.44-0.47; M vein ratio 0.43-0.54; halter stem dark brown; knob white to whitish yellow. Femora black; tibiae blackish brown except for basal and apical extremities black; tarsi mostly yellowish orange. Abdomen: Tergites shiny black. Male terminalia : Epandrium in posterior view (Fig 45) as a broadly rounded, inverted U, width of dorsal portion slightly narrower than lateral arms, lateral arms shallowly arched, in lateral view wider ventrally; cercus in posterior view (Fig 45) almost evenly semilunate, robustly developed at dorsal and ventral margins; aedeagus in lateral view (Fig 47) slipper-like, base wide with moderately narrow, thumb-like projection at connection with phallapodeme, tapered more or less evenly to moderately rounded apex, in ventral view (Fig 47) with basal 1/3 expanded laterally from narrow base, thereafter to apex slightly tapered then parallel to bilobed apex, each lateral lobe as wide as aedeagal base, with thin, short, wing-like, narrow projections sub-basally; phallapodeme in lateral view (Fig 47) robustly lunate, basal margin broadly and conspicuously rounded, narrowed at each apex, in ventral view (Fig 46) longer than wide, T-like, with long, apical crossbar, apical margin shallowly emarginate; ejaculatory apodeme in lateral view L-shaped, in ventral view broadly ovate; postgonite in lateral view (Fig 47) as a parallelogram, acutely pointed basally and apically, bearing 2-3 setulae along basoposterior margin and 1 setula subapically along margin toward hypandrium; pregonite in lateral view (Fig 47) moderately elongate, almost parallel sided, tapered, narrowed Distribution (Fig 48). Nearctic: Canada (Alberta, Northwest Territories, Ontario, Yukon Territory). United States (Idaho, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, New Mexico, Ohio, Oklahoma, South Dakota, Texas, Virginia, Wisconsin). Palearctic: Austria, Belgium, Czech Republic, Morocco, Romania, Russia (European Territory), Spain.
Remarks. This species is rarely collected and may be uncommon in nature. In the Delmarva States (United States), this species occurs along the coastal plain and in the Alleghany and is expected to be found between these zones.
Although uncommon, this species is relatively distinctive and is similar to G. bohemanni, in having pale, usually yellowish maxillary palpi, antennae, and foretibiae. This species is distinguished from G. bohemanni as follows (also see key): The anterolateral area of the mesonotum, just mediad of the area from the postpronotum through the notopleuron is thinly microtomentose and is subshiny to shiny with some metallic luster; the lateral mesonotal area from and including the postpronotum and notopleuron in males is thinly whitish microtomentose, similar to the central mesonotal microtomentum; and the midtibiae are dark colored. ( (Fig 49) as a broadly formed, inverted U, somewhat rounded quadrate, with the base more narrowly formed, dorsal portion more thinly developed than lateral arms, lateral arms shallowly arched to nearly straight, curved medially subapically, enlarged ventrally, broadly rounded, setulae more clustered at ventral margin; cercus in posterior view (Fig 49) elongate,semilunate, lateral margins arched, medial margins nearly straight, nearly uniformly setulose but slightly more clustered at ventral margin; aedeagus in lateral view (Fig 52) slongate, narrowly slipperlike, nearly straight, base shallowly emarginate, tapered very slightly toward apex, long margins nearly parallel sided, apex moderately broadly rounded, in ventral view ( Fig  50) expanded sub-basally with narrow, laterally flaring processes, thereafter very slightly expanded to apex, essentially parallel sided, apex broadly rounded; phallapodeme in lateral view (Fig 51) more or less irregularly triangular, extension toward hypandrium slightly more elongate than extension towards aedeagal base, in ventral view (Fig 50) T-shaped, apical crossbar moderately robust, length of each flared arm about half width of stem; ejaculatory apodeme in lateral view straight, base expanded, extended process digitiform, in ventral view almost bar-like with bump near midlength; postgonite in lateral view (Fig 51) irregularly bar-like, pointed basally, widest just before midlength, thereafter slightly tapered, apex robustly digitiform, bearing 3 setulae along posterior margin and 1 setula subapically along anterior margin, in ventral view (Fig 50) as an elongate triangle, wide basally, length of tapered sides about twice basal width, apex narrowly rounded, lateral margins shallowly emarginate, straight medially; pregonite in lateral view (Fig 51) clavate, pointed on portion toward hypandrium, rounded on opposite end, in ventral view (Fig 50) ovate with rounded pointed; hypandrium in ventral view (Fig 50) with anterior margin broadly rounded, thereafter posteriorly with lateral margin concave, posterior margin moderately deeply and widely U-shaped, in lateral view (Fig 51)  Remarks. This species is very similar and is probably closely related to the G. cinerella (Stenhammar) in the Old World but is distinguished from that species by the shape of structures of the male terminalia (see figures). From Nearctic congeners, this species is distinguished by the yellowish to slightly reddish maxillary palpi and the black scape and pedicel. ( Diagnosis. This species is distinguished from congeners by the following combination of characters: Small to moderately small shore flies, body length 1.95-2.85 mm; generally black dorsally with moderately to sparse microtomentum . Head: Frons grayish black, moderately to sparsely microtomentose, subshiny. Scape black; pedicel black basally, apicoventrally yellow; basal flagellomere slightly darkened dorsally, otherwise yellow to reddish yellow, sometimes wholly so; arista bearing 5 dorsal rays. Facial microtomentum generally yellow to slightly brownish yellow; parafacial and gena grayish microtomentose, contrasted with gold-yellow color of face; gena moderately high, gena-to-eye ratio 0.13-0.18. Maxillary palpus yellow to red. Thorax: Mesonotum slightly grayish black to black, sparsely microtomentose, subshiny to shiny; pleural area largely like mesonotum, sometimes more grayish to tannish black. Wing hyaline; costal vein ratio 0.37-0.45; M vein ratio 0.55-0.60. Coxae, femora, and tibia grayish black to black; tarsi yellow, apical tarsomeres becoming darker, brownish yellow. Abdomen: Tergites Partially subshiny to mostly shiny black, very sparsely microtomentose. Male terminalia (Figs 53-55): Epandrium in posterior view (Fig 54) as a broadly formed, inverted U with the base more narrowly formed, dorsal portion more thinly developed than lateral arms, lateral arms shallowly arched, enlarged ventrally, broadly rounded, setulae more clustered at ventral margin; cercus in posterior view (Fig 53) elongate,semilunate, lateral margins arched, medial margins irregularly straight, setulae more clustered at ventral margin; aedeagus in lateral view (Fig 55) slipper-like, base shallowly emarginate, tapered very gradually toward apex, apical half nearly parallel sided, apex moderately broadly rounded, in ventral view (Fig 54) expanded laterally from narrow base on basal 1/3, thereafter to apex almost parallel sided, slightly tapered, apical margin shallowly incised medially, bilobed; phallapodeme in lateral view (Fig 55) more or less irregularly triangular, extension toward hypandrium more elongate than angle towards aedeagal base, in ventral view (Fig 54) I-shaped, apical crossbar robust, wider than basal crossbar, Distribution (Fig 56). Nearctic: Canada (Alberta, British Columbia, Ontario, Quebec), United States (Alaska, Colorado, Idaho, ?Maine [literature record, not confirmed; Cresson 1924: 160], Michigan, Oregon, Washington, Wyoming). Palearctic: Finland, Japan (Hokkaido), Mongolia (Töv).

Gymnoclasiopa tacoma
Remarks. This species is relatively widespread in the Nearctic Region and in the Old World, we have examined specimens from Finland, Japan, and Mongolia.
This species is distinguished from congeners by the yellowish to yellowish red antennae and maxillary palpi coupled with the black fore-and midtibiae, which are similar in color to the femora.

Nearctic species excluded from Gymnoclasiopa
In our world catalog , we transferred two Nearctic species, D. cana Cresson and D. canifrons Cresson, from Ditrichophora to Gymnoclasiopa. This transfer was based on external characters. We have now examined structures of the male terminalia of these two species, and from this evidence, we suggest that their proper placement is in Ditrichophora. Like other species in Ditrichophora, these two species have a rounded epandrium, a single gonite (probably the postgonite) that is not divided into pre-and postgonites, and a phallapodeme that is somewhat Y-shaped in lateral view. Details concerning these two species, including diagnoses, follow. Diagnosis. This species is distinguished from congeners by the following combination of characters: Moderately small to medium-sized shore flies, body length 2.40-3.60 mm; head and thorax generally microtomentose gray dorsally, abdomen subshiny to shiny black. Head: Frons moderately microtomentose, cinereous to whitish; proclinate fronto-orbital setae 2, length of anterior seta about 1/2 that of posterior seta, inserted far anteriad, distance between proclinate setae subequal to that between posterior seta and medial vertical seta. Antenna generally black, especially scape and pedicel; arista bearing 6-7 dorsal rays. Face rather flat; antennal grooves, especially ventral margins, poorly defined, not conspicuous; face slightly whitish gray dorsally, dorsal portion shallowly carinate between shallow antennal grooves, thinly, microtomentose, becoming blackish, less microtomentose ventrally; facial setae inserted close to parafacials, aligned vertically; gena short, less than height of basal flagellomere; gena-to-eye ratio 0.15-0.16. Maxillary palpus black. Thorax: Mesonotum moderately microtomentose, cinereous, similar to frons, not shiny; pleural areas from ventral notopleural suture ventrad black, contrasted with whitish gray mesonotum, similar to black abdominal tergites. Wing lacteous, more so in males; costal section II conspicuously longer than costal section III; costal vein ratio 0.47-0.51; M vein ratio 0.52-0.56; halter stem yellowish; knob white to whitish yellow. Femora black; tibiae black, including basal and apical extremities black; foretarsus black dorsally, yellowish ventrally; mid-and hindtarsi mostly yellowish orange. Abdomen: Tergites subshiny to shiny, black. Male terminalia: Epandrium in posterior view as an inverted U, narrowed dorsally, abruptly so medially with moderately deep incision, in lateral view widest subventrally with ventral margin rounded and bearing cluster of longer setulae, these becoming longer toward posteroventral angle; cercus in posterior view uniformly semilunate with dorsomedial margin more narrowly pointed; aedeagus in lateral view longer than wide, as anterior and posterior structures, anterior portion longer than posterior portion and with a long flap folded back on itself (as in Pectinifer aeneus (Cresson)), in ventral view robust, narrow ventrally; phallapodeme in lateral view with elongate, irregularly triangular keep, processes at either end about equal in length, in ventral view robustly T-shaped with thick stem, base as wide as cross bar; gonite head and thorax generally microtomentose gray dorsally, abdomen subshiny to shiny black. Head: Frons moderately microtomentose, cinereous to whitish; proclinate fronto-orbital setae 2, length of anterior seta about 1/2 that of posterior seta, inserted far anteriad, distance between proclinate setae subequal to that between posterior seta and medial vertical seta. Antenna generally yellowish orange (sometimes apex of basal flagellomere and scape darkened); arista bearing 7-8 dorsal rays. Face rather flat; antennal grooves, especially ventral margins, poorly defined, not conspicuous; face slightly whitish gray dorsally, dorsal portion shallowly carinate between shallow antennal grooves, thinly, microtomentose, becoming blackish, less microtomentose ventrally; facial setae inserted close to parafacials, aligned vertically; gena short, less than height of basal flagellomere; gena-to-eye ratio 0.08-0.09. Maxillary palpus black. Thorax: Mesonotum moderately microtomentose, cinereous, similar to frons, not shiny; pleural areas from ventral notopleural suture ventrad black, contrasted with whitish gray mesonotum, similar to black abdominal tergites. Wing lacteous; costal section II conspicuously longer than costal section III; costal vein ratio 0.47-0.65; M vein ratio 0.54-0.57; halter stem yellowish tan to yellow, knob yellowish white to white. Femora black; tibiae black except for basal and apical extremities black; tarsi mostly yellowish orange. Abdomen: Tergites subshiny to shiny, black. Male terminalia: Epandrium in posterior view as an inverted U, narrowed dorsally, each lateral arm shallowly curved; cercus in posterior view semilunate with dorsomedial, narrow extension; aedeagus in lateral