Revision of New World Species of the Shore-fly Subgenus Allotrichoma Becker of the Genus Allotrichoma with Description of the Subgenus Neotrichoma (Diptera, Ephydridae, Hecamedini)

Abstract The New World species of the subgenera Allotrichoma Becker and Neotrichoma (new subgenus) are revised, including a phylogenetic analysis of the species groups and subgenera within the genus Allotrichoma. For phylogenetic perspective and to document the monophyly of the genus Allotrichoma and its included subgenera and species groups, we also provide a cladistic analysis of genera within the tribe Hecamedini. The ingroup included seven exemplar congeners from within Allotrichoma. Outgroup sampling included exemplars of other genera within Hecamedini and from the putative sister group, Lipochaetini, and to root the analysis, we used an exemplar of the tribe Discocerinini. Analyses with successive weighting and implied weighting recovered a monophyletic Allotrichoma and indicated clades within the genus. Eight new species are described (type locality in parenthesis): Allotrichoma bifurcatum (Utah. Utah: Lake Shore (40°06.9'N, 111°41.8'W; 1370 m)), Allotrichoma dynatum (Oregon. Benton: Finley National Wildlife Refuge (44°24.6'N, 123°19.5'W)), Allotrichoma occidentale (Oregon. Lake: Lakeview (44 km E; Drake Creek; 42°11'N, 119°59.3'W)), Allotrichoma robustum (California. Kern: Kern River (35°16.1'N, 119°18.4'W)), Allotrichoma sabroskyi (New Mexico. Sandoval: La Cueva (Junction of Highways 126 and 4; 35°52'N, 106°38.4'W; 2342 m)), Allotrichoma wallowa (Oregon Baker: Goose Creek (35 km E Baker City; 44°49.2'N, 117°27.79'W; 825 m)), Allotrichoma baliops (Florida. Monroe: Key West (Willie Ward Park; 24°32.9'N, 81°47.9'W)), and Allotrichoma insulare (Dominica. Cabrits Swamp (15°35'N, 61°29'W)). Within Allotrichoma, we recognize three subgenera of which one, Neotrichoma (type species: Allotrichoma atrilabre), is newly described. All known species from the New World are described with an emphasis on structures of the male terminalia, which are fully illustrated. Detailed locality data and distribution maps for the New World species are provided. A lectotype is designated for Discocerina simplex Loew and a neotype is designated for Allotrichoma bezzii Becker. Allotrichoma filiforme Becker, Allotrichoma trispinum Becker, and Allotrichoma dahli Beschovski are reported as new synonyms of Allotrichoma simplex (Loew) and Allotrichoma yosemite Cresson is a new synonym of Allotrichoma atrilabre Cresson. We also clarify the status of previously described species, including those with Holarctic distributions. For perspective and to facilitate genus-group and species-group recognition, the tribe Hecamedini is diagnosed and a key to included genera is provided.


Introduction
Only a few genera of shore flies (Diptera: Ephydridae) have greater species diversity in the Old World than in the New and also have the extant diversity in the New World primarily found in temperate areas of the Nearctic Region, sometimes exclusively so. Examples of these distributional and diversity patterns within shore flies are the genera Ephydra Fallén (Wirth 1971(Wirth , 1975 and Allotrichoma Becker. The latter genus, Allotrichoma, is the subject of this revision, and why and how its distributional pattern developed and what the New World species-level diversity is have in part prompted this research. This revision also complements relatively recent and ongoing research on the Old World fauna of Allotrichoma (Krivosheina and Zatwarnicki 1997), since we also sought to know if any species found in the Palearctic Region actually occurs in the Nearctic Region, as has been reported (Cresson 1942, Wirth 1965, Mathis and Zatwarnicki 1995. Finally, discovering the phylogenetic relationships of taxa within and related to Allotrichoma, including relationships among taxa above the species level, continues to intrigue us and is also investigated here. The discovery and correct identification of species and then accurately characterizing them are fundamental and preliminary steps to any research on the classification and distribution of shore flies. Problems associated with inaccurate species identification of Allotrichoma became apparent when the genus was first proposed. Becker (1896) first described Allotrichoma and designated Hecamede lateralis Loew as its type species. The type species, A. laterale, was also reported to occur in North America (Cresson 1942, Wirth 1965, but these records were apparently based on misidentifications and have not been confirmed herein. In the same paper, however, and based on specimens collected in Italy, Becker also described A. bezzii, a species that we have discovered in the Nearctic Region, and thus to have a Holarctic distribution. Moreover, the first species to be described from the Nearctic Region was A. simplex (Loew 1861), which we have discovered to also have a Holarctic distribution and to have junior synonyms that are based on specimens collected in Europe. Thus, the clarification and in some cases the correct determination of what species are represented in the Nearctic Region is a necessary first and crucial step to any elaboration of zoogeographic and/or phylogenetic relationships.
In addition to Loew and Becker's species, A. simplex and A. bezzii, Cresson (1926) described four species: A. lasiocercum, A. lacteum, A. atrilabre, and A. yosemite. We (Mathis and Zatwarnicki 2010) recently added A. deonieri, which was described as part of a study on the fauna of the Delmarva States. No other species have been described from the Nearctic Region. These species, with the exception of A. deonieri, were included in Cresson's (1942) review of Nearctic shore flies, and some of these species have also been listed in more localized faunal papers, such as Johnson's (1925) list of New England flies, and in papers dealing with natural history, such as Runyan and Deonier (1979). Faunistic and natural history papers are noted in the synonymy of each respective species. Wirth (1965Wirth ( , 1968 and Mathis and Zatwarnicki (1995) included all then known species in their respective catalogs.
Although most speciose genera of Nearctic shore flies have been treated comprehensively in the last 30 years (Mathis and Zatwarnicki 1995), an exception is Allotrichoma sensu stricto. Certainly, the small size of adults, which are usually less than 2.50 mm in body length, has detracted from their study, but Wirth (1965) identified a more generic concern in his annotation to this genus in his catalog (Wirth 1965) of Nearctic shore flies. Wirth noted that the species of Allotrichoma were poorly understood and that revision should include study of structures of the male terminalia to clarify the species and their distributions. Implied, although not stated, is that specimens are virtually indistinguishable externally. This study confirms Wirth's observation, and following his suggestion and what we have observed in our own studies, we have relied wholly on structures of the male terminalia to make species-level identifications. Thus the key and species' descriptions rely substantially on these structures.
In this revision, we more than double the number of species known from the New World with six of 12 species in the subgenus Allotrichoma being described herein, and in a newly described subgenus, Neotrichoma, two of the three species from the New World are also described. We also clarify the status of previously described species, including those with Holarctic distributions.
To provide phylogenetic perspective to this revision, we studied all genus-group taxa within the tribe Hecamedini and reassessed their cladistic relationships. Our phylogenetic study for taxa within the genus Allotrichoma was done at the species-group level, and we attempted to approach this globally by examining species from throughout the world and placing them into appropriate species groups. This global approach was done in an effort to adhere to the recommendations of Schmid (1979) and Schefter (2005), i.e., "Recognition of monophyletic groups of species as genera without reference to the world fauna might engender taxonomic inflation at the generic level and thereby erode the cognitive value of the genus."

Methods and materials
The descriptive terminology, with the exceptions noted in Mathis (1986b) and Mathis and Zatwarnicki (1990a) and below, follows that published in the Manual of Nearctic Diptera (McAlpine, 1981). Specimens of Allotrichoma are small and 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 (see references in Mathis 1986b, and Mathis and Zatwarnicki 1990a, 1990b, such as surstylus. Zatwarnicki (1996) has suggested that the pre-and postsurstylus correspond with the pre-and postgonostylus and that the subepandrial plate is the same as the medandrium. The terminology for structures of the male terminalia is provided directly on Figs 3-7 and is not repeated for comparable illustrations of other species. Alternative spellings for some localities are cited in parenthesis, especially for locality names that were transliterated into English. Species' descriptions are composite and not based solely on the holotypes, and paired structures are described in the singular except where the context makes this inappropriate. Two venational ratios used in the descriptions are based on the largest, smallest, and one other specimen and are defined below: 1. Costal vein ratio is the straight line distance between the apices of veins R 2+3 and R 4+5 divided by the distance between the apices of veins R 1 and R 2+3 . 2. M vein ratio is the straight line distance along vein M between crossvein dm-cu and r-m divided by the distance apicad of crossvein 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.
The phylogenetic analysis was performed with the assistance of Hennig86© and TNT©, computerized algorithms that produces cladograms by parsimony. Character data were polarized primarily using outgroup procedures. Although autapomorphies were not included in the cladistic analysis (they were made inactive), which would skew the consistency and retention indices, we listed them on the cladogram and included them as part of generic treatments and phylogenetic considerations to document the monophyly of the lineages, particularly at the generic level.
Because only males can now be accurately identified at the species level, we have limited paratype series of new species to that gender only. This practice became especially apparent when we discovered that species of Allotrichoma often occur together, with up to four or five species being found at the same locality (La Cueva, New Mexico; Goose Creek, Oregon; Deadman Canyon, Utah; Swasey Beach, Utah). Thus, not now being able to distinguish females and to make positive, species associations of males and females often precludes designating females as paratypes.
Although dissection of male abdomens is ordinarily needed to make species-level identifications, many specimens have these structures exposed, which facilitate their examination. When we pin adult males before they have dried, we often gently squeeze the abdomen slightly, usually extruding these structures, or we carefully tease these structures out with a pin.
Dissections of male terminalia were performed using the method of Clausen and Cook (1971) and Grimaldi (1987). Microforceps were used to remove abdomens, which were macerated in a potassium hydroxide solution. Cleared genitalia were rinsed in water and then transferred to glycerin for observation and illustration. Abdomens were placed in an attached plastic microvial filled with glycerin and attached to the pin supporting the remainder of the insect from which it was removed.
Although most specimens for this study, including the primary types, are in the National Museum of Natural History (USNM), numerous others were borrowed, particularly type specimens of the species previously described. To our colleagues and their institutions listed below who loaned specimens, we express our sincere thanks. Without their cooperation this study could not have been completed. alar seta lacking; posterior notopleural seta inserted at distinctly elevated position, especially as compared to anterior seta; anepisternum usually two toned, dorsal portion concolorous with mesonotum, ventral portion gray; anepisternum with 2 subequal setae inserted along posterior margin. Wing: venation of wing generally pale colored; vein R 2+3 elongate, section III much shorter than section II; apical section of vein M longer than section between crossveins r-m and dm-cu; alula wide, width subequal to that of costal cell. Abdomen: Male terminalia: Pregonite either lacking or fused indistinguishably with postgonite; subepandrial sclerite lacking; postgonite generally elongate and bearing few setulae, usually only 2 are conspicuous.
Phylogenetic considerations. Mathis (1991) placed Allotrichoma in the tribe Hecamedini Mathis (subfamily Gymnomyzinae), and in his proposed phylogeny for genera within Hecamedini, Allotrichoma and related genera comprised the most derived lineages within the tribe. In this study, we have re-examined the evidence, all morphological characters, in an attempt to discover more definitively the phylogenetic placement of Allotrichoma and related taxa, especially those taxa that have been treated as subgenera within Allotrichoma. The basic question is "What are the phylogenetic relationships (hypothetical) among taxa closely related to or within Allotrichoma?" As background, we first present a summary of the evidence and relationships at the tribal level (within Gymnomyzinae) and then proceed to the evidence and our analysis of it for taxa within Hecamedini.
With the phylogenetic background for further study of the tribe Hecamedini within the subfamily Gymnomyzinae established and the monophyly of Hecamedini documented, we now proceed with the cladistic analysis and resultant relationships among the included genera, but with a few explanatory remarks first. In the presentation on genus-level relationships that follows, the characters used in the analysis are listed first.
Each character is immediately followed by a discussion to explain its states and to provide perspective and any qualifying comments about that character. After presentation of the information on character evidence, an hypothesis of the cladistic relationships is presented and briefly discussed. A detailed, species-level phylogeny is beyond the scope of this paper, especially as Allotrichoma sensu stricto is essentially found worldwide except for the Neotropical Region, and herein we focus primarily on the New World fauna. Our intent here is to present evidence and an analysis of that evidence in an attempt to determine intermediate clusters of taxa, such as subgenera and species groups within Allotrichoma. We have allocated all taxa within Allotrichoma to one of three subgenera (Allotrichoma, Neotrichoma, Pseudohecamede), and within the subgenus Allotrichoma, four species groups (alium, dyna, laterale, and simplex species groups). The New World species of the subgenus Allotrichoma are in two of the species groups: laterale (A. bezzii, A. deonieri, A. dynatum, A. lacteum, A. lasiocercum, A. occidentale, A. robustum, A. sabroskyi, and A. schumanni) and simplex (A. bifurcatum, A. simplex, and A. wallowa). The cladogram (Fig. 2) is the primary mode to convey relationships, and the discussion is to supplement the cladogram and is intended only to complement the latter. In the discussion of character data, a "0" indicates the state of the outgroup; a "1" or "2" indicates the derived states. Multistate characters (1,2,3,4,6,9,11,12,15,17,18,25,31,33,34,40,43,44,45,46,47,49,50,51), which comprise 46 percent of the total number, were treated as nonadditive (-), and characters. The numbers used for characters in the presentation are the same as those on the cladogram, and the sequence is the same as noted in the charac- ter matrix (Table 1). For polarization of character states within Hecamedini, we used the tribes Lipochaetini (Glenanthe Haliday and Lipochaeta) and Discocerinini (Discocerina obscurella) as the successive outgroups in this phylogenetic analysis. Runyan and Deonier (1979) cited six morphological characters from immature stages in their preliminary phylogenetic analysis. While these may have phylogenetic significance, we know so little about these characters for the taxa being treated that we are hesitant to use them. The majority of taxa would be represented by a question mark in the matrix, as we known virtually nothing about their distribution among related taxa. Hopefully this revision will promote further research on immature stages, including field work, and allow us to incorporate these kinds of characters into an analysis.  (8) Interfrontal setae (an interfrontal seta in addition to ocellar setae, which are usually inserted more anteriorly, usually just anterior of anterior ocellus in Hecamedini): (0) lacking (Discocerina, Glenanthe, Lipochaeta, Diphuia, Elephantinosoma, Eremotrichoma, Allotrichoma sensu lato, Hecamede nuda); (1) present (Hecamede albicans). 7 (9) Aristal setae (nonadditive): (0) bearing 5-10 dorsally branching rays more or less evenly along arista (Discocerina); (1) bearing 3-5 dorsally branching rays, longer 2-3 rays subequal, inserted toward aristal base (a synapomorphy for the tribes Gymnomyzini, Hecamedini); (2) a brush, with short setulae both dorsally and ventrally (Lipochaetini). 8 (10) Microsetulae on compound eye: (0) bearing microsetulae (Discocerina, Lipochaetini, and also Hydrelliinae, probably through convergence);

Characters
(1) lacking microsetulae or these very sparse (Gymnomyzinae except for Lipochaetini). 9 (11) Facial conformation (nonadditive): (0) distinctly but shallowly convex (Lipochaeta); (1) (1) with an anterobasal process (Neotrichoma); (2) narrowly rectangular to almost tubular (Allotrichoma sensu stricto); (3) lacking a gonite (Glenanthe, Lipochaeta). 14 (50) Apical gonal setulae (nonadditive): (0) several setulae, especially along dorsal margin (Hecamede, Diphuia); (1) 2 setulae, usually 1 apical, the other apicoventral (Allotrichoma sensu stricto); (2) 1 subapical setulae (Elephantinosoma); Analysis and results. Using the implicit enumeration (ie*) option of Hennig86 and TNT, which is an exhaustive search, 29 most parsimonious trees were generated from the analysis of the 53 characters. The cladograms have a length of 135 steps and consistency and retention indices of 0.64 and 0.65 respectively. The matrix was then subjected iteratively to successive weighting (xs w, ie*, cc) to determine a character's contribution or weight (Carpenter 1988, Dietrich andMcKamey 1995). We also used the implicit weighting option in TNT. The successive weighing stabilized at 559 steps, and with stabilization, the consistency and retention indices increased to 0.89 and 0.90, respectively. Both successive and implicit weighting schemes resulted in the same two cladograms. One of these cladograms is identical to one of the 29 original trees and is our cladogram of choice ( Fig. 2), being one of the most parsimonious cladograms. The two cladograms only differ in the terminal relationships of the simplex species group, i.e., whether it forms a tritomy or whether the simplex group is the sister group to the other species groups in the subgenus Allotrichoma. The analysis of characters for this cladogram is given in Table 2 and the weights of the various characters are given in Table 3.
In summary and as indicated on the cladogram (Fig. 2), the tribe Hecamedini is a monophyletic lineage (unambiguous synapomorphies 10 and 37) that is closely related to Lipochaetini (the outgroup), and these two tribes together (Hecamedini and Lipochaetini) are particularly well supported (synapomorphies 7, 18, 21, 24, 29, 34, and 39). The typology of the genera within Hecamedini, including subgenera within Allotrichoma, forms a stepwise hierarchy, beginning with Diphuia as the sister group Table 2. Analysis of characters based on the cladogram ( Figure 2  to all other genera (see Mathis and Marinoni 2010, for a review and further discussion of Diphuia), followed by the subgenera within the genus Hecamede (see Mathis 1993 for a revision and further discussion of Hecamede). The next lineage in the hierarchy is Elephantinosoma, an Old World genus (see Mathis and Deeming 1987, for a revision and further discussion of Elephantinosoma.), followed by Eremotrichoma, which is likewise an Old World genus. Eremotrichoma, which we continue to accord generic status following recent precedent, now includes six species (Mathis 1986a, Canzoneri and Vienna 1989, Krivosheina 1992. All further lineages (from Neotrichoma to the end), which are the more derived lineages, are interpreted to be the genus Allotrichoma with the names of taxa denoting subgenera and species groups. This follows the precedent of Mathis (1991) and Mathis and Zatwarnicki (1995). Neotrichoma, which is a new subgenus being proposed herein, is the first lineage within Allotrichoma and is the sister-group to the remaining subgenera and species groups. The monophyly of this Neotrichoma is well established, as is its immediate sister-group, the node giving rise to the subgenera Pseudohecamede (see Mathis 1991, for a revision and further discussion of Pseudohecamede) and Allotrichoma. Likewise, note that Pseudohecamede and Allotrichoma are well established and well documented subgenera.

Diagnosis.
Allotrichoma is distinguished from other genera of the tribe Hecamedini by the following combination of characters: small to moderately small shore flies, body length 1.15-2.95 mm. Head: Wider than high in anterior view; frons wider than high, entirely and mostly densely microtomentose, with vestiture of mesofrons undifferentiated except by color; ocellar setae lacking; 1 well-developed pair of intrafrontal setae inserted in front of anterior ocellus; a reclinate fronto-orbital seta and a proclinate fronto-orbital seta present, reclinate seta inserted slightly anteromediad of proclinate seta; pseudopostocellar setae present, usually well developed; both inner and outer vertical setae present; ocelli in isosceles triangle, with distance between posterior pair slightly larger than between anterior ocellus and either posterior ocellus. Antenna exerted; aristal length subequal to antennal length and bearing 4-6 dorsal rays, with basal 3-4 rays longer than apical 1-2, subequal. Eye apparently bare of microsetulae (using stereomicroscope). Face with dorsal ½-3/4 carinate between antennae; ventral margins curved inward laterally making oral margin narrow, width subequal to narrowest distance between eyes, anterior margin shallowly emarginate; bearing 2 facial setae, the dorsal one very slightly larger, both inserted near parafacials; labella broad, fleshy, shorter than mediproboscis.
Abdomen: Fifth tergite of male not visible from a dorsal view, telescoped within 4th. Natural History. Adults generally feed on nectar from different flowering-plant species and oviposit upon various kinds of decomposing organisms and excrement (Deonier, in litt.).
For purposes of agreement between species-group names and genus-group names, the generic name Allotrichoma is neuter, not feminine.
The following is a key to the subgenera presently included in the genus. Diagnosis. Small to moderately small shore flies, body length 1.15-2.40 mm. Head: Frons mostly unicolorous, at most with narrow, anterior fronto-orbits slightly lighter in color, lacking distinctively colored ocellar triangle; pseudopostocellar setae subequal in length to intrafrontal setae. Pedicel with well-developed, proclinate, dorsal seta. Facial coloration sexually dimorphic, males unicolorus and darker; face with dorsal 2/3 between antennal grooves shallowly carinate, becoming more prominent ventrad of antennal grooves, slightly tuberculate; clypeus usually mostly microtomentose, dull colored; palpus blackish.
Abdomen: Fifth tergite tubular, elongate, well sclerotized, length subequal to that of 4th, bearing a posteroventral process in conjunction with 5th sternite; 5th sternite highly modified, produced as a ventral flap or processes. Male terminalia: cerci well sclerotized, elongate, often twice length of epandrium (probably used at least partially as a clasping structure); surstylus fused to ventral margin of epandrium, usually appearing as an elongate extension of the epandrium (secondarily lost in some species), bearing apical setulae; a single gonite (presumably fused pre-and postgonites) sheathing aedeagus; aedeagus simple, tubelike, sometimes slightly arched; hypandrium generally reduced, fused basally to base of gonite, in lateral view appearing strap or bar-like.
Distribution. Except for polar regions and South America, the subgenus Allotrichoma occurs worldwide, although with greater diversity in temperate zones (Mathis and Zatwarnicki 1995).
Natural history. Very little is known about the natural history of any species of Allotrichoma, especially larval habitats and immature stages. The brief and few references are as follows: From the island of Guam, Bohart and Gressitt (1951: 85) wrote that "Adults [of apparently A. livens Cresson] swarm around foul-smelling mud and puddles and are especially abundant in the mud of pig pens around feeding troughs where contamination by garbage and pig feces is heavy. The larvae breed in pig droppings and pupate at the surface of the droppings. Although maggots were not observed in the contaminated mud of pig pens, it is probable that most of them develop there." "This fly is extremely common wherever found. It is apparently not present around mud which is free from contamination. It probably has no medical significance, and control is unnecessary." Bohart and Gressitt (1951: plate 11) also presented an illustration of the puparium of A. livens. Runyan and Deonier (1979: 123-137) summarized information on the natural history of Allotrichoma and published the only illustrations on the eggs, puparia, and cephalopharyngeal skeleton of A. (A.) simplex and A. (P.) abdominale and the egg of A. (N.) atrilabre (as A. yosemite). They also reported that specimens of these three groups occur in habitats that are rich in decaying organic matter, including limnic wrack, stag-nant pools, and vertebrate excrement (muskrat, raccoon, horse, pig, and cow feces). Sand shores and piles of lawn clippings were also added as habitats for adults, which have also been swept from the inflorescences of a wide variety of plant species. Runyan, the senior author of this paper, also collected adults on dead fish and crayfish carcasses.
We too have collected adults from the kinds of habitats reported above but emphasize that much of our success in collecting was on fairly undisturbed, sandy shores associated with both lotic and lentic aquatic systems, sometimes with the adjoining shore having alkali and perhaps other salts. Moreover, we often found several species occurring microsympatrically together. We commonly found two species together and at a few sites in the West, we collected up to five species occurring together. Based on this finding, we have been especially hesitant to designate females as paratypes, not knowing how to distinguish between them, from localities where multiple species occur. Our discovery begs the question about how these various species are partitioning the habitat where and when they occur together microsympatrically.
Discussion. The monophyly of this subgenus is corroborated by several characters that Runyan and Deonier (1979) and more recently that Krivosheina and Zatwarnicki (1997) have identified. These synapomorphies are as follows: (1) Surstylus (=gonostylus; fused to epandrium, therefore called surstylus) as a simple appendix, terminating with apical setulae, or secondarily reduced; (2) gonites incised apically; (3) cerci generally elongate, in some tropical species fused to each other, rarely oval; (4) 5th sternite with a ventrally produced, paired, lateral flap (one flap on each side) and a medial process; (5) 4th tergite of male largely vestigial, forming two small bands close to the anterior margin of 5th tergite.
An objective of this revision was to report the determination of species that may have a Holarctic distribution, as noted in the introduction. For example, among the seven species reported from the Nearctic Region, Wirth (1965) listed two, A. laterale (Loew) and A. trispinum Becker, with Holarctic distributions. Wirth also cautioned (1965: 736), however, that "The species are poorly understood and distributions records need revision after a study of male genitalia." Our research, which has emphasized characters from structures of the male terminalia, indeed reports not two but three Holarctic species, but none is one of the species names that Wirth reported earlier. The Holarctic species reported in this revision are: A. bezzii, A. schumanni, and A. simplex. The first two are species first named from specimens collected in Europe and then discovered here, and the last species, A. simplex, has as its type locality, "Maryland," and has now been found to be the senior synonym of taxa occurring in Europe. We call attention to these discoveries to emphasize that studies of limited geographic scope, such as this revision of New World species, need to consider congeners on a global basis to avoid misidentifications and incorrect distributional data.
We can presently identify only males of this subgenus, and as a consequence, we have only used structures of the male terminalia in the key to the New-World species of this subgenus that follows. Cercus with apex rounded (best seen in lateral view); male 5th sternal flap in lateral view (Fig. 5) shallow but long, bearing numerous, tuberculate setae; 5th medial process ( Fig. 4)  Cercus in lateral view comparatively more robustly developed to apex and bearing numerous setulae along length (Figs 51-53); surstylar extensions straight (Fig. 53)   Description. This species is distinguished from congeners by the following combination of characters: Small to moderately small shore flies, body length 1.35-2.30 mm (Fig. 1). Head: Medial facial carina above facial prominence shallow; labella broad, fleshy, shorter than mediproboscis; clypeus microtomentose, usually gray. Thorax: Presutural supra-alar seta present. Wing with costal vein ratio 0.27-0.33; M vein ratio 0.38-0.44.
Type material. Although Zatwarnicki (1991: 298) designated a lectotype for this species, that designation is invalid, not being based on a syntype. According to Becker's diary (ZMHU), the specimen selected as the lectotype was collected in 1897, a year after publication of this species (1896), and therefore, it could not be a syntype. We and others (Maurizio Pavesi, MSNM) have searched for the type series of this species in Becker and Bezzi's collections without success. Thus to stabilize the nomenclature of this species, we have determined that a neotype should be designated and have selected the so-called lectotype as the neotype.  [red]." The neotype is double mounted, is in generally good condition (abdomen removed and dissected; structures in an attached microvial), and is deposited in the ZMHU.  Distribution (Fig. 8). Nearctic: Canada (Saskatchewan), Mexico (Baja California, Jalisco), United States (Alaska, Arizona, California, Colorado, Idaho, Minnesota, Montana, Nevada, New Mexico, North Dakota, Oregon, Texas, Utah, Washington, Wyoming). Palearctic: Afghanistan, Austria, Bulgaria, Croatia, France, Germany, Hungary, Italy, Lithuania, Poland, Russia (European Territory), Slovenia, Spain, Sweden, Yugoslavia.
Remarks. In the Nearctic Region, this species has been found thus far only in the West, including Alaska, and the locality data suggest that the species probably also occurs in the western provinces of Canada.
As noted in the synonymy, many previous records of this species occurring in the New World were cited as A. laterale, a common misidentification. In the Palearctic Region, Zatwarnicki (1991) and Mathis and Zatwarnicki (1995) listed two European species as being conspecific with A. bezzii: Allotrichoma lena Dahl (1973: 354: Afghanistan. Herat: Bala Murghab (470 m); HT ♂) and A. pedemontanum Canzoneri and Meneghini (1979: 629: Italy. fiume Po a Torino; HT ♂). We confirm their conspecificity here and thus, that these names are synonyms.
Etymology. The species epithet, bifurcatum, is of Latin derivation and refers to the bifurcate apex of the surstylus of this species.
Remarks. The distribution of this species is somewhat related to the Great Basin in western North America, where current climatic conditions are semiarid, although there is a northern extension into northern Idaho and British Columbia. Better sampling may reveal this species to be more widespread. Description. This species is distinguished from congeners by the following combination of characters: Small shore flies, body length 1.20-1.95 mm. Head: Medial facial carina above facial prominence shallow; labella broad, fleshy, shorter than mediproboscis; clypeus microtomentose, usually gray. Thorax: Presutural supra-alar seta present. Wing with costal vein ratio 0.31-0.39; M vein ratio 0.38-0.40.
Type material. The holotype male Allotrichoma deonieri is labeled "USA. Etymology. The species epithet, deonieri, is a genitive patronym to honor one of the collectors of this species, D. L. Deonier, a long-time student of shore flies. Dick is not only our friend and colleague but an excellent field biologist. His collecting efforts have greatly assisted our research on shore flies.
Remarks. Although most records of this species are from the drainage of the Mississippi River, including nearby tributaries, the records from Maryland and Virginia represent a completely different drainage system. Description. This species is distinguished from congeners by the following combination of characters: Small to moderately small shore flies, body length 1.40-2.00 mm. Head: Medial facial carina above facial prominence shallow; labella broad, fleshy, shorter than mediproboscis; clypeus microtomentose, usually gray. Thorax: Presutural supra-alar seta present. Wing with costal vein ratio 0.35-0.36; M vein ratio 0.47-0.52.

Allotrichoma (Allotrichoma) dynatum
Abdomen: Male 5th sternal flap in lateral view (Fig. 25) relatively shallow but long, bearing 6-8, tuberculate setae; 5th medial process in lateral view (Fig. 25) robust, greatly enlarged basally, with a posterior projection, broadly pointed apically, bear row of setulae anteroapically. Male terminalia (Figs 21-24): Epandrium in posterior view (Fig. 21) ovately rounded on dorsal half, wider than high; epandrium in lateral view ( Fig. 22) with anterior and posterior margins of dorsal half nearly straight and parallel sided; cercus robust, thick, in posterior view (Fig. 21) pointed dorsally, gradually broadened ventrally then rather abruptly curved laterally and ventrally as a slightly tapered, elongate process that bears numerous long setulae apically and along posterior margin; cercus in lateral view (Fig. 22) slightly curved, wider dorsally, ventral half nearly parallel sided, apex broadened and bearing setulae; surstyli in posterior view as parallel, narrow, elongate processes that bear setulae on apical portion, apex narrowly rounded; surstylus in lateral view shallowly curved, basal half slightly tapered, apical half almost parallel sided, apical portion bearing short setulae, apex tapered to narrow point; aedeagus in ventral view (Fig. 23) elongate, moderately narrowly ovate, tapered apically, in lateral view (Fig. 24) narrowly elongate, somewhat lunate; phallapodeme in lateral view (Fig. 24) very narrowly triangular, digitiform keel shorter than length, pointed; gonite in ventral view (Fig. 23) bar-like, very slightly wider basally, apex with  short, lateral process, apex bearing setula, in lateral view (Fig. 24) wide basally, gently curved, tapered to apical point, with a subapical, short process that bears a setula. Etymology. The species epithet, dynatum, is derived from the Greek work dynamis, meaning strong or powerful, alluding to the well-developed cerci of this species.

Allotrichoma (Allotrichoma) lacteum
Remarks. Like A. bezzii, this species occurs in the western United States, although not as far north as Alaska.
Although similar to A. sabroskyi, the greatly widened surstylus that bears numerous short setulae easily distinguishes this species from it and all other congeners. Description. This species is distinguished from congeners by the following combination of characters: Small to moderately small shore flies, body length 1.55-2.15 mm. Head: Medial facial carina above facial prominence shallow; labella broad, fleshy, shorter than mediproboscis; clypeus microtomentose, usually gray. Thorax: Presutural supra-alar seta present. Pleural area lacking stripes. Wing with costal vein ratio 0.36-0.38; M vein ratio 0.37-0.40. Legs blackish brown to black; midtibia bearing numerous, erect setae along dorsal surface.
Etymology. The species epithet, occidentale, refers to the western distribution of this species in the Nearctic Region.
Remarks. This species is closely related to A. bifidum Papp (1975), which was relatively recently described from specimens collected in Hungary. The morphological differences between these two species are relatively slight but consistent and are especially evident in the shape of the extended cercus. The distal apex of the cercus in A. occidentale is only slightly flared; whereas in A. bifidum the apex is conspicuously and consistently much wider. Given these consistent differences and its pronounced allopatry with A. bifidum, we have elected to treat this species as separate and distinct.   tively narrow dorsally, becoming wider ventrally than tapered to a broad point; cercus very robust, in posterior view (Fig. 45) as a elongate, pendulous, ventrolaterally projected process, becoming wider ventrally, apex flared, truncate, bearing numerous, long to very long setulae, very long setulae apicolaterally; cercus in lateral view (Fig.  46) essentially straight, widest subapically, then narrowed to blunt, ventral apex, some very long setulae curved apically or irregularly contorted; surstyli (ventral extensions of epandrium) in posterior view as nearly parallel, shallowly arched medially, narrow processes that bears a few setulae apically, surstylus in lateral view (Fig. 46) conspicuously arched, narrow, very slightly tapered process, not expanded apically; aedeagus in ventral view (Fig. 47) elongate, narrowly ovate, slightly tapered apically, in lateral view (Fig. 48) elongate, narrow, nearly straight; phallapodeme in lateral view (Fig. 48) narrowly triangular, keel narrow, prong-like, shorter than length, almost digitiform; gonite in ventral view (Fig. 47) somewhat bar-like, lateral margin shallowly sinuous, notched basally and medially pointed apically, bearing a subapical, ventral setula and an apical setula; gonite in lateral view (Fig. 47) wide basally, conspicuously but gently curved and tapered toward apex, with a subapical, setula and an apical setula.
Etymology. The species epithet, sabroskyi, is a genitive patronym to honor Curtis W. Sabrosky. Curt was our mentor and friend and always had time to assist and respond to our numerous questions. Abdomen: Male 5th sternal flap in lateral view (Fig. 61) moderately and irregularly elongate, bearing several, tuberculate setulae apically; 5th medial process in lateral view (Fig. 61)   verted, laterally rounded, almost oval U; epandrium in lateral view (Fig. 58) relatively narrow dorsally, becoming wider ventrally, slightly projected posteroventrally; cercus in lateral view (Fig. 58) essentially straight, wide dorsally, than narrowed but very gradually becoming wider ventrally, as wide subapically as dorsal width, then tapered more abruptly to narrowly rounded apex, apex bearing long and apically curved setulae especially evident on ventral margin; cercus in posterior view (Fig. 57) as a elongate, somewhat pendulous, ventrally projected process, gradually becoming wider ventrally, apex truncate to very shallowly emarginate at an oblique angle, apex slightly longer laterally than medially, apex bearing numerous, very long setulae; surstyli (ventral extensions of epandrium) in posterior view as parallel, narrow processes that bear setulae on apex, apex not broadened or curved; surstylus in lateral view narrow, elongate, conspicuously curved, apical portion not expanded, bearing setulae apically; aedeagus in ventral view (Fig. 59) elongate, narrowly ovate, slightly tapered apically, in lateral view ( Fig. 60) elongate, shallowly and narrowly lunate; phallapodeme in lateral view (Fig.  60) narrowly triangular, keel shorter than length, almost digitiform; gonite in ventral view (Fig. 59) somewhat bar-like, lateral margin very shallowly concave, with short, subapical, medial process, apex of process bearing a setula, and a short, apical process that likewise bears a short setula; gonite in lateral view (Fig. 60) wide basally, gently curved and tapered toward apex, with a subapical, short process that bears a setula and an apical setula.
Natural history. Deonier (1965: 501) found this species to be "occasional" in mud shore and sand shore habitats but rare in sedge meadow and Eragrostis mat habitats. Runyan and Deonier (1979) produced the only illustrations of immature stages, including an egg, the cephalopharyngeal skeleton of the third instar larva, and the puparium.
Remarks. This species has a Holarctic distribution, and Palearctic specimens have been named at least three different times, with A. simplex being the senior synonym. The junior synonyms in chronological order are: A. filiforme Becker (1896), A. trispinum Becker (1896), and A. dahli Beschovski (1966a). In Europe, there is also a very similar species, A. strandi Duda, that differs only slightly but apparently consistently from this species. In males of A. simplex, the cercus has four apical setulae, compared to three in A. strandi, and the mesonotal stripes are more evident in A. strandi than in A. simplex.
In the Nearctic Region, this is a common species that may have the most widespread distribution. Description. This species is distinguished from congeners by the following combination of characters: Small shore flies, body length 1.30-1.95 mm. Head: Medial facial carina above facial prominence shallow; labella broad, fleshy, shorter than mediproboscis; clypeus microtomentose, usually gray.
Abdomen: Male 5th sternal flap in lateral view (Fig. 70) moderately elongate, bearing 3 long setulae apically; 5th medial process in lateral view (Fig. 70) very elongate, nearly straight, apex widened, bearing 4-5 apical setulae. Male terminalia (Figs 69,(71)(72)(73): Epandrium in posterior view (Fig. 69) rounded dorsally, constricted laterally at base of surstyli; epandrium in lateral view (Fig. 73) somewhat rectangular dorsally with anterior and posterior margins parallel sided, ventral portion with an anterior bulge and a narrow, sharp incision at about level of base of surstylus; cerci in posterior view (Fig. 69) approximate dorsally then extended laterally to form a lyre-like structure that curves laterally than ventrally, apex of cercus bearing 2 short setulae; cercus in lateral view (Fig. 73) shallowly sinuous, nearly parallel sided, apex not expanded, bluntly rounded; surstyli (ventral extensions of epandrium) in posterior view as relatively wide at base third, thereafter ventrally abruptly narrowed, especially along medial margin, to form an elongate process that is slightly spatulate apically, apical portion bearing several short setulae; surstylus in lateral view (Fig. 73) moderately narrow, slightly expanding with apex obliquely pointed, anteroventral surface of apex shallowly emarginate,  Etymology. The species epithet, wallowa, is a noun in apposition and refers to the Wallowa Mountains in northeastern Oregon. The headwaters of Goose Creek are in the Wallowas.
Remarks. This species is similar and closely related to A. simplex, differing from that species in the shape of the surstylar apex and especially in the shape of the male 5th sternal flap and process.
Diagnosis. Minute to small to moderately small shore flies, body length 0.85-1.45 mm.
Etymology. The species epithet, baliops, is of Greek derivation, meaning spotted, and is a noun in apposition that alludes to the spotted face of this species.
Remarks. The known distribution of this species is obviously disjunct, which is undoubtedly the result of sampling error, i.e., a lack of field work and collecting. Al- though specimens are apparently uncommonly collected, we suggest that this species will eventually be found at localities between and beyond those presently indicated. More field work by competent collectors is needed.