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SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 345

Studies of Ephydrinae (Diptera: Ephydridae), VI: Review of the Tribe Dagini

Wayne N. Mathis

SMITHSONIAN INSTITUTION PRESS

City of Washington

1982

ABSTRACT

Mathis, Wayne N. Studies of Ephydrinae (Diptera: Ephydridae), VI: Review of the Tribe Dagini. Smithsonian Contributions to Zoology, number 345, 30 pages, 89 figures, 1982.—Dagini, new tribe, comprising the genera Diedrops Mathis and Wirth, Physemops Cresson, Dagus Cresson, and Psilephydra Hendel, is reviewed. The systematics and classification of these genera have been confused, with their placement varying from the subfamily Parydrinae to Ephydrinae. Here they are placed in Ephydrinae and are recognized as a separate tribe. The basis for this arrangement and the monophyly of the tribe are discussed. A cladogram of the tribe is proposed that elaborates relationships between genera. The phylogeny, as now conceived, is an unresolved trichotomy, with the following lineages: Diedrops, Psilephydra, and the stem lineage that gave rise to Dagus and Physemops. The latter two taxa are suggested to be sister genera. Species of the included genera are systematically reviewed, and for the genus Physemops a hypothetical phylogeny is suggested that has the genus divided into two species groups: the nemorosus group and the panops group. Character evidence for these conclusions are given. Keys to genera, species groups, and species and appropriate illustrations are provided.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus).

Library of Congress Cataloging in Publication Data

Mathis, Wayne N

Studies of Ephydrinae (Diptera, Ephydridae)

(Smithsonian contributions to zoology; no. 285, 295, 303, 325, 329, 345)

Includes bibliographies.

Contents: 1. Revisions of Parascatella Cresson and the triseta group of Scatella Robineau-Desvoidy.—2. Mathis, W. N. Phylogeny, classification, and zoogeography of nearctic Lamproscatella Hendel.—[etc.]—6. Mathis, W. N. Review of the tribe Dagini.

Supt. of Does, no.: SI 1.27:285, etc.

1. Ephydridae. I. Shewell, Guy E., joint author. II. Wirth, Willis Wagner, joint author. III. Title. IV. Series Smithsonian Institution. Smithsonian contributions to zoology; no. 285 [etc.]

QL1.S54 no. 285, etc. [QL537.E7] 591s 78–606062 [595.77′4] AACR1

Contents

Introduction

Historical Review

Methods

Acknowledgments

Subfamily EPHYDRINAE Zetterstedt

DAGINI, new tribe

Key to Genera of Dagini

Genus Diedrops Mathis and Wirth

Key to Species of Diedrops

1. Diedrops aenigma Mathis and Wirth

2. Diedrops hitchcocki Mathis and Wirth

Genus Physemops Cresson

Key to Species of Physemops

The nemorosus Group

3. Physemops azul Wirth

4. Physemops nemorosus (Cresson)

5. Physemops wheeleri Wirth

The panops Group

6. Physemops fairchildi Wirth

7. Physemops maldonadoi Wirth

8. Physemops panops Wirth

Genus Dagus Cresson

9. Dagus rostratus (Cresson)

Genus Psilephydra Hendel

Key to Species of Psilephydra

10. Psilephydra cyanoprosopa Hendel

11. Psilephydra fluvialis (Miyagi), new combination

Literature Cited

Requirements for Smithsonian Series Publication

FIGURE 1.—Habitus of Dagus rostratus, female.

Studies of Ephydrinae (Diptera: Ephydridae), VI: Review of the Tribe Dagini

Wayne N. Mathis

____________

Wayne N. Mathis, Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560.

Introduction

While conducting studies on the subfamily Ephydrinae, I encountered several problematic genera that were not easily accommodated within existing classifications, particularly at the tribal level. In the past, with my own research, I have either dealt with these genera by simply noting their existence and that they were probably members of the subfamily Ephydrinae (Mathis, 1979b) or I have not treated them at all, as they did not belong to any existing tribe, as then characterized, and the studies were limited to those tribes (Mathis, 1980).

The problem does not lie solely with the problematic genera but is also a reflection of the inadequate classifications. The tribe Scatellini, for example, is obviously paraphyletic, as noted previously (Mathis, 1979b, 1980), which indicates the need for further resolution at the suprageneric level.

To remedy these conditions, I am reviewing the problematic genera, here recognized as the tribe Dagini, with the immediate objective of providing perspective for the group within the subfamilial classification. In many respects the results to be presented are preliminary, and other adjustments will undoubtedly be necessary as further data are discovered that relate to questions of relationship within the subfamily. For the present, however, I am bringing existing information forward and presenting an overview of the group, somewhat in synoptic form, but also with new data and a reinterpretation.

It is hoped that this study will prompt further research on the group, particularly the natural history of the included species. To date, neither the immature stages nor the natural history of any of the species is known.

HISTORICAL REVIEW.—The history of the genera and species now included in Dagini is relatively recent, with the first reference dating to Williston (1896), who described Ephydra pygmaea. Unfortunately, the name Williston chose was preoccupied (Haliday, 1833), and the species is not a member of the genus Ephydra Fallén, as noted and changed by Cresson (1918, Ephydra rostrata Cresson, new name; 1935, species assigned to Dagus). In 1914, Hendel and Cresson published on additional species now included in Dagini: Hendel described Psilephydra cyanoprosopa from Taiwan, as a new genus and species, and Cresson described a second species in that genus, P. nemorosa, from Costa Rica. Some years later, Cresson (1934) proposed the genus Physemops, with Psilephydra nemorosa as type-species, and a year afterward (1935) he erected the genus Dagus, with Ephydra rostrata as type-species. After a 35–year hiatus of work on the included genera and species, Wirth (1970) revised the genus Physemops, adding five more species: P. azul, P. fairchildi, P. maldonadoi, P. panops, and P. wheeleri. More recently, Mathis and Wirth (1976) described the genus Diedrops, which included two new species: D. aenigma, as type-species, and D. hitchcocki.

In previous studies dealing with various taxa now comprising Dagini, considerable divergence of opinion was expressed concerning the affinities of the included genera. Cresson (1914, 1934) was of the opinion that the genera Psilephydra and Physemops were allied with the subfamily Parydrinae and enumerated several apparent similarities between these two genera and several genera of Parydrinae (genera of Parydrinae used in his comparison included Hydrina of Robineau-Desvoidy (= Hyadina Haliday), Axysta Haliday, Gastrops Williston, Lytogaster Becker, and Parydra Stenhammar). Later, when Cresson described the genus Dagus (1935), he allied that genus with the tribe Ephydrini, subfamily Ephydrinae. Character evidence for this alliance was as follows (Cresson, 1935:345): “The laterally curved frontorbitals, the prominent setulose medi-facies, the long rather straight claws and rudimentary pulvelli [sic], place this genus in the tribe Ephydrini.”

In a recent revision of the genus Physemops, Wirth (1970:170) stated that

some of the most striking characteristics of P. nemorosus [the type-species of Physemops] are of a specific nature. The presence in some of these species of distinct series of dorsocentral and acrostichal bristles, and of a pair of enlarged bristles on the medifacies suggests that Physemops belongs in the subfamily Ephydrinae. Examination of the Oriental Psilephydra cyanoprosopa Hendel reveals that it is related to Physemops on one hand and to the Polynesian genus Apulvillus Malloch on the other.

The disposition of Apulvillus, as a subgenus of Scatella Robineau-Desvoidy, was dealt with in an earlier study (Mathis, 1980).

When Mathis and Wirth (1976) described Diedrops, they noted several similarities between it and Psilephydra. In their summary of generic relationships (p. 128), they mentioned that “Diedrops is probably most closely allied with the subfamily Parydrinae, but it shares many characters with the Ephydrinae and perhaps is an annectant genus.”

In 1977, Mathis published a key to the Neotropical genera of the subfamily Parydrinae and commented on several of the genera. His key included Physemops and Diedrops largely because previous authors had associated both genera with Parydrinae. Mathis noted several possible relationships with taxa in the subfamilies Parydrinae and Ephydrinae but also noted (1977:556) that “it is obvious that the relationships of the Physemops-group with other ephydrid taxa are poorly known. An evaluation of pertinent characters, to determine their relative derived versus primitive states will be necessary before the sequence of lineages can be better clarified.”

Finally, in a preliminary study of the subfamily Ephydrinae, Mathis (1979b) stated that Dagus and related genera (Diedrops, Physemops, and Psilephydra) should be included in Ephydrine as a distinct sublineage. No clarification, however, as to the relationships of this sublineage with other lineages of Ephydrinae was then elaborated, and in his tentative classification of Ephydrinae, this sublineage, with its included genera, was listed as “Group VII.”

METHODS.—The general methods used in this study were explained in previous parts of this series (Mathis and Shewell, 1978; Mathis, 1979a, 1980; Mathis and Simpson, 1981). Three aspects, however, are newly incorporated in this study.

One of the major objectives of this study is to bring published but scattered taxonomic data together that relates directly to Dagini. In consequence of this goal, I have purposely written descriptions more in the style of diagnoses, with some additional elaboration. Moreover, the section on the genus Physemops is to a large extent a synthesis of Wirth's (1970) previous revision. In view of this level of descriptive treatment, the headings to the appropriate sections are labeled “Diagnostic Description,” and these sections take the place of having separate diagnosis and description sections.

In previous parts of this series, wing ratios were expressed as components, e.g., costal vein ratio 1: 0.25. Here I have simply carried out the appropriate division, and the ratios are given as a single number, i.e., costal vein ratio 4.

In previous publications, I have either separated the combining adjectives “fore-” and “mid-” from the nouns they modified or have used noncombining, anglicized counterparts, such as front or middle. Here I am using the combining form of these adjectives. Their proper use requires the formation of a single word, the combining adjective plus the noun being modified, e.g., foreleg, midtarsi, etc.

ACKNOWLEDGMENTS.—Most specimens I examined are housed in the National Museum of Natural History, Smithsonian Institution, although material was also borrowed from other institutions. To the curators of these collections and their respective institutions, I express my grateful thanks for their cooperation. Designations of all collections, as cited in the text, are as follows.

ANSP

Academy of Natural Sciences of Philadelphia, Pennsylvania (Drs. Daniel Otte and Curtis Dunn)

BMNH

British Museum (Natural History), London, England (Mr. Brian H. Cogan)

CAS

California Academy of Sciences, San Francisco, California (Dr. Paul H. Arnaud, Jr.)

NMW

Naturhistorisches Museum, Vienna, Austria (Dr. Ruth Contreras-Lichtenberg)

USNM

former United States National Museum, collections in the National Museum of Natural History, Smithsonian Institution, Washington, D.C.

I also wish to acknowledge the following individuals for providing information or rendering special service: Miss Hollis B. Williams for general assistance; Mr. Young Sohn and Ms. Molley K. Ryan for executing the habitus illustrations; Mrs. Susann G. Braden and Ms. Mary-Jacque Mann for taking the electron micrographs; Mr. Victor E. Krantz for taking photographs of the wings; and Miss Noreen Connell for typing the various drafts of the manuscript. Finally I wish to thank Drs. Willis W. Wirth and Paul J. Spangler for critically reviewing the manuscript.

Subfamily EPHYDRINAE Zetterstedt

DIAGNOSIS.—Members of this subfamily closely resemble those of Parydrinae but may be distinguished from them and those of other subfamilies by the following combination of characters: fronto-orbital bristles present, lateroclinate, usually 2, although number variable; face generally transversely arched; clypeus concealed; midfacies bearing setulae or setae, facial series of setae frequently convergent dorsally; oral opening usually large and cavernous, oral margin often ciliate with setae, these sometimes long; mesopleuron with a single large bristle inserted along the posterior margin at about midheight, frequently with smaller bristles dorsally and ventrally; vein R2+3 usually long, terminating much closer to vein R4+5 than to R_1; larvae generally in mud, secondarily in algal mats and excrement.

DISCUSSION.—As characterized here, the subfamily Ephydrinae agrees with the concept of most authors of this century (Cresson, 1930:112, 1931:104; Sturtevant and Wheeler, 1954:154–161; Wirth and Stone, 1956:463; Dahl, 1959:105; Wirth, 1965:753, 1968:22; Hennig, 1973:62; Cogan and Wirth, 1977:338; Miyagi, 1977:81; Cogan, 1980:668). The concept and characterization were developed primarily by Cresson (1930), with most subsequent authors following his precedent.

The subfamily is doubtlessly monophyletic, as established by the character evidence (see “Diagnosis” above). Its sister group, however, has not been identified, although I suggest that it will be found to be either the subfamily Parydrinae as a whole or an included taxon of that subfamily. Parydrinae may be paraphyletic, and perhaps the classifications of Dahl (1959) and Miyagi (1977), which further divide Parydrinae into other subfamilies, will have merit. The cladistic relationships of Parydrinae and its included taxa need clarification.

DAGINI, new tribe

DIAGNOSIS.—Specimens of Dagini are similar to those of Scatellini and Ephydrini but are distinguished by the following combination of characters: face shieldlike, uniformly and shallowly protrudent, lacking distinctly protrudent dorsal facial prominence in lateral view (Dagus has a ventral prominence); frons uniformly dark colored, brownish black and usually contrasting with lighter colored face, lighter facial coloration usually due to whitish to silvery white tomentum, especially on ventral portion; lacking cruciate intrafrontal bristles inserted near anterior margin of face; dorsocentral and acrostichal series lacking large presutural bristles but usually with 1–3 large postsutural dorsocentral bristles, rarely with a prescutellar pair of acrostichal bristles; anterior notopleural bristle and sternopleural bristles frequently weak, especially as compared with posterior notopleural bristle and mesopleural bristle respectively; lacking a supra-alar bristle; prosternum bare of setulae; hind coxal strap bare of setulae; pulvilli generally present (except for Dagus), tarsal claws conspicuously curved and short; propleuron bare of setulae (except for Diedrops); coloration generally dull to subshiny brown dorsally, contrastingly gray below with a rather sharp demarcation between the coloration change (except for Physemops).

PHYLOGENETIC CONSIDERATIONS.—Following an earlier arrangement (Mathis, 1979b), I have tentatively placed Dagini as a third lineage of a trichotomy within Ephydrinae. The other two lineages of the trichotomy are Ephydrini and Scatellini. The tribal relationships of the subfamily Ephydrinae need further resolution.

In the diagnosis of Dagini, several exceptions are noted. I consider them to be secondary developments to the basic ground plan of the tribe, and, for the most part, they represent autapotypies of their respective taxa. In the presentation of character evidence to follow, the numbers accompanying the discussion of a particular character correspond with those used on the cladogram.

Dagini is apparently a monophyletic group, although the character evidence is not overwhelming.

1. Sternopleural bristle: Generally in Ephydrinae the sternopleural bristle is as well developed as the mesopleural bristle, but in most lineages of Dagini, the sternopleural is conspicuously weaker than the latter.

2. Conformation of face: In several genera of Parydrinae and nearly all genera of Ephydrinae, the face is transversely arched, the oral opening is large, sometimes gaping, and there are usually distinct antennal foveae. The genera of Dagini also have the face vertically arched, usually lacking distinct antennal foveae, and the face extends ventrally, giving the appearance of a shield.

The four genera now included in Dagini are schematically arranged as outlined in Figure 2. The basic branching sequence is an unresolved trichotomy, with each lineage comprising the trichotomy having its probable monophyly established by character evidence without clarification as to the relationships between them.

FIGURE 2.—Hypothetical phylogeny for tribe Dagini (based on character evidence in text).

Diedrops is monotypic. Its monophyly is established as follows:

3. Vestiture of propleuron: With few exceptions (Ephydrini and Teichomyza Macquart) the propleuron is bare of setae or setulae in Ephydrinae. The setulose propleuron in species of Diedrops is a synapotypic condition.

4. Ocellar bristles: Ocellar bristles are generally present throughout the family Ephydridae. Their absence in species of Diedrops is likewise a synapotypy.

5. Apical position of vein R2+3: Vein R2+3 is usually relatively long in Ephydrinae, terminating about as far from vein R4+5 as the latter is from vein M. In species of Diedrops, however, vein R2+3 ends much closer to vein R4+5, at about half the distance between R4+5 and vein M. This character is unique to Diedrops.

Psilephydra is probably monophyletic, with evidence as follows:

6. Shape of gonite: The shape of the gonite in the two known species of Psilephydra appears to be unique within the tribe and not only characterizes the genus but is evidence to establish its monophyly. See generic and species treatments for descriptions of the shape and illustrations (page 24).

7. Shape of the aedeagal apodeme: In both known species of this genus, the aedeagal apodeme is very slender, apparently a condition unique to Psilephydra.

I have tentatively allied Dagus with Physemops as sister groups. This relationship and the monophyly of their joint stem lineage are established as follows:

8. Position of posterior notopleural bristle: Generally the posterior notopleural bristle is inserted at about the same level as the anterior bristle. In species of Dagus and Physemops, the posterior bristle is inserted at a level distinctly higher than that of the anterior bristle, and this I interpret to be a synapotypy.

The monophyly of the genus Physemops is established as follows:

9. Number and orientation of fronto-orbital bristles: The generalized ground plan of Ephydrinae is for two lateroclinate fronto-orbital bristles. In species of Physemops the anterior fronto-orbital bristle is lost, and the posterior bristle is oriented posterolaterally.

10. Genal bristle: The species of Physemops lack a genal bristle. Wtih the exception of Psilephydra cyanoprosopa, this condition is unique within Dagini, and I interpret it to be synapotypic and to have arisen independently in both Physemops and Psilephydra.

11. Upper facial setae: A character of Ephydrinae is the presence of facial setae, and frequently there is an outstanding row of larger setae extending from the midfacial height to the posteroventral corner. In species of Physemops, the distinct row, as described, is lacking, but there is a conspicuous pair of porrect, divergent setae at the midfacial height that is unique to the genus.

The monophyly of the genus Dagus is established as follows:

12. Vestiture of humeral callus: In most genera of Ephydrinae, the humeral callus is either bare of setulae or bears conspicuous setae that are large, bristle-like. In species of Dagus, the humeral callus is mostly bare except for one or two small setulae that are sometimes difficult to see except in profile.

13. Pulvilli: Dagus is the only genus of the tribe where the pulvilli are lacking, and I interpret this condition to be autapotypic.

14. Shape of the face: In most species of Dagini, the face is shieldlike and shallowly protrudent. In the only known species of Dagus, however, the lower one-half to two-thirds of the face is distinctly protrudent and is evenly arched both horizontally and vertically.

Key to Genera of Dagini

Genus Diedrops Mathis and Wirth

Diedrops Mathis and Wirth, 1976:126 [type-species: Diedrops aenigma Mathis and Wirth, by original designation].—Mathis, 1977:555 [generic key].

DIAGNOSIS.—Specimens of Diedrops resemble those of Psilephydra, Dagus, and Physemops but may be distinguished by the following combination of characters: ocellar bristles lacking; lateroclinate fronto-orbital bristles 2, sometimes weakly developed; mesofrons in depression; arista moderately long, although not twice length of first 3 antennal segments, minute setulae on at least basal two-thirds, sometimes to apex; third antennal segment nearly twice length of second segment; face shieldlike, shallowly and evenly protrudent over entire height; facial setae uniformly sparse and subequal in size except those along oral margin, especially laterally, the latter setae longer, lacking facial series extending from midfacial height to posteroventral angles of face; genal bristle present, conspicuous; 1 pair of larger prescutellar acrostichal bristles; scutellar bristles variable as to comparative lengths; humeral callus bare of setulae; anterior notopleural bristle only slightly smaller than posterior one; posterior notopleural bristle inserted at about the same height as anterior bristle; propleuron with scattered setulae; sternopleural bristle conspicuously weaker than mesopleural bristle; apex of vein R2+3 approximate to vein R4+5, distance between these less than one-half that between veins R4+5 and M; capitellum of halter with some blackish gray, thinly tomentose areas; forefemur lacking row of spinelike setae.

MALE TERMINALIA.—Fifth sternum divided, each sternite with setulae more densely clustered toward posteromedian angle. Epandrium shieldlike, cerci and cercal cavity occupying dorsal one-half to one-third, ventral margin emarginate, setulose, and perhaps representing fused surstyli; gonite at least 3 times higher than wide, with gonal arch posterodorsally, latter with median, ventral projection; aedeagal apodeme comparatively large, J-shaped, ventral portion wider; aedeagus 2–3 times longer than wide in lateral view, variously shaped.

PHYLOGENETIC CONSIDERATIONS.—Although the monophyly of Diedrops is well established (see Figure 2, with accompanying character evidence), its relationship within the tribe remains unresolved. Externally the general habitus of the included species closely resembles that of Psilephydra cyanoprosopa, but character evidence to support this relationship is presently lacking.

GEOGRAPHIC DISTRIBUTION.—New World tropics: Mexico (Michoacan and Sinaloa) and Peru (Mariscal Nieto).

DISCUSSION.—Our knowledge of Diedrops is presently limited to minimal taxonomic data. Since description of the genus, no other species have been discovered, no additional specimens from different localities have been collected, and nothing is known about the natural history of the included species.

Key to Species of Diedrops

1. Diedrops aenigma Mathis and Wirth

FIGURES 3–10

Diedrops aenigma Mathis and Wirth, 1976:129.

DIAGNOSTIC DESCRIPTION.—Resembling D. hitchcocki but differing from it as follows: larger species, length 4.13 to 4.53 mm.

Head: Frons width-to-length ratio 1 :0.23; vestiture of frons uniformly tomentose, appearing dull, mesofrons not distinguished from parafrons; anterior surface of face nearly vertical, very slightly protrudent only at dorsal prominence; facial setae comparatively shorter and less conspicuous; eye width-to-face length ratio 1 :0.43; anteroventral margin of eye rounded; eye-tocheek ratio 1 :0.84.

Thorax (Figure 8): Setae of dorsocentral and acrostichal series generally less well developed, usually lacking a larger pair of prescutellar acrostichal setae; anteroventral scutellar bristle well developed, subequal in length to apical scutellar bristle; length of basitarsus equal to or shorter than combined length of remaining tarsomeres for each leg; capitellum of halter relatively lighter in color, with considerable pale coloration. Wing (Figure 8): apex rounded; vein R2+3 more or less evenly and shallowly arched throughout its length, costal vein ratio 23; vein M ratio 1.35.

Abdomen (Figures 3–9): Dorsum concolorous with mesonotum; fifth tergum of male almost as long as wide; male terminalia as in Figures 3–7; female ventral receptacle as in Figures 8, 9.

TYPE-LOCALITY.—MEXICO. Michoacan: Puerto Morillos (a park workers' settlement in Atzimba National Park, located on Mexico Route 15, approximately 28 miles east of Morelia and about a mile west of the summit of Puerto Garnica, elevation 2825 m).

PRIMARY TYPE MATERIAL.—The holotype male is labeled “Puerto Morillos Mich[oacan]. MEXICO VIII-24-1959/L. A. Stange A. S. Menke Collectors/HOLOTYPE Diedrops aenigma Mathis & Wirth [red; handwritten].” The holotype is directly pinned, is in fairly good condition (slightly tattered, some setae missing), and is in the California Academy of Sciences, CAS 12426.

GEOGRAPHIC DISTRIBUTION.—Mexico (Michoacan and Sinaloa).

REMARKS.—In the small series of this species I examined, all that are apparently available, considerable variation exists with regard to number and size of setae, particularly those along major setal tracks, i.e., frontal-orbital bristles, dorsocentral bristles.

FIGURES 3–10.—Diedrops aenigma: 3, internal male genitalia, lateral aspect; 4, same, posterior aspect; 5, male terminalia, lateral aspect; 6, epandrium and cerci, posterior aspect; 7, fifth tergites, ventral aspect; 8, wing; 9, female ventral receptacle, lateral aspect; 10, same, anterior aspect.

2. Diedrops hitchcocki Mathis and Wirth

FIGURES 11–26

Diedrops hitchcocki Mathis and Wirth, 1976:129.

DIAGNOSTIC DESCRIPTION.—Resembling D. aenigma but differing from it as follows: smaller species, length 2.78 to 3.52 mm.

Head (Figures 11, 12, 19–22): Frons width-to-length ratio 1 :0.29; vestiture of frons with mesofrons more thinly tomentose, subshiny, contrasting with dull appearing more densely tomentose parafrons and fronto-orbits; anterior surface of face in lateral view conspicuously longer at oral margin than at dorsal prominence, relatively more arched vertically; facial setae longer and more conspicuous; eye width-to-face length ratio 1 :0.67; anteroventral margin of eye acutely rounded; eye-to-cheek ratio 1 :0.95.

Thorax (Figures 13, 23–26): Setae of dorsocentral and acrostichal series generally more strongly developed; usually with a larger pair of prescutellar acrostichal setae; anteroventral scutellar bristle weakly developed, usually less than one-half length of apical scutellar bristles; length of basitarsus longer than combined length of remaining tarsomeres for each leg; capitellum of halter comparatively darker, mostly blackish gray, with pale coloration restricted to less than one-half total surface. Wing (Figure 16) with apex bluntly rounded; vein R2+3 evenly arched on basal three-fourths, thereafter shallowly dipping toward vein R4+5; costal vein ratio 27.5; vein M ratio 1.31.

Abdomen (Figures 14, 15, 17, 18): Dorsum usually lighter in color than mesonotum; length of third tergum only slighter shorter than combined length of fourth and fifth terga; fifth tergum truncate apically, not longer than wide; male terminalia as in Figures 14, 15, 17, 18.

TYPE-LOCALITY.—PERU. Moquegua: Yacango (a village in the arid zone, Torata District, Mariscal Nieto Province, Department of Moquegua, in the valley of the Rio Osmore, elevation 1875 m).

FIGURES 11–18.—Diedrops hitchcocki: 11, head, lateral aspect; 12, same, anterior aspect; 13, thorax, dorsal aspect; 14, internal male genitalia, lateral aspect; 15, same, posterior aspect; 16, wing; 17, fifth tergites, ventral aspect; 18, epandrium and cerci, posterior aspect.

PRIMARY TYPE MATERIAL.—Holotype male is labeled “5 IX [IX crossed out] X 1965 Yacango MOQUEGUA, PERU 197 Coll. J. C. Hitchcock, Jr. [day, crossing out of IX, and “197” handwritten]/ /a red rectangle/HOLOTYPE Diedrops hitchcocki Mathis & Wirth [red; handwritten].” The holotype is double mounted (minute nadel in a cork base), is in good condition (a few setae of the head missing), and is in the National Museum of Natural History, Smithsonian Institution, USNM 71116.

GEOGRAPHIC DISTRIBUTION.—This species is known only from the type-locality.

REMARKS.—Setae, especially the larger ones, of the major setal tracks are apparently more stable in this species than in its congener. My sampling, however, is limited to the series from the type-locality.

FIGURES 19–26.—Diedrops hitchcocki: 19, head, lateral aspect; 20, same, dorsal aspect of left side; 21, occlli, dorsal aspect; 22, genal bristlc, lateral aspect; 23, notopleuron and bristles, lateral aspect; 24, scutellum, dorsal aspect; 25, mesopleuron, dorsum of sternopleuron, and bristles, lateral aspect; 26, midleg, lateral aspect of fifth tarsomere, claws, and pulvilli.

Genus Physemops Cresson

Physemops Cresson, 1934:211 [type-species: Psilephydra nemorosa Cresson, by original designation and monotypy].—Wirth, 1968:20 [catalog of Neotropical species]; 1970: 170–177 [review].—Mathis, 1977:555, 556 [generic key and discussion].

DIAGNOSIS.—Specimens of Physemops resemble those of Dagus, Psilephydra, and Diedrops but may be distinguished by the following combination of characters: ocellar bristles variable, present or absent (see species group diagnoses); posterolateroclinate fronto-orbital bristle 1, sometimes weakly developed; aristal length variable from about twice combined length of first 3 antennal segments to 3 to 4 times length of latter, usually with setula-like rays, sometimes in 2 rows; third antennal segment short to normally long; face shieldlike, shallowly and uniformly protrudent; facial setae mostly short, those along oral margin longer especially laterally, uniformly scattered, sometimes with a larger pair at midheight, lacking facial series extending from mid-dorsal facial prominence to posteroventral angle; genal bristle lacking; prescutellar acrostichal setae generally lacking; scutellar bristles with anterior pair distinctly smaller than posterior pair, usually the former less than one-half the latter; humeral callus bare of setulae; anterior notopleural bristle weaker than posterior one; posterior notopleural bristle inserted at level distinctly above that of anterior bristle; propleuron bare of setulae; sternopleural bristle weak as compared with mesopleural bristle; apices of vein R2+3 and R4+5 at normal distance apart, distance between them about equal to that between veins R4+5 and M; forefemur lacking row of spinelike setae.

MALE TERMINALIA.—Epandrium variously shaped, providing excellent characters at the species level, usually well sclerotized, with no evident surstyli along ventral margin, the latter probably fused indistinguishably with epandrium; gonite in lateral view much longer than wide, usually with posterior, narrow projection; aedeagal apodeme usually small, straplike, frequently concealed in lateral view; aedeagus variously shaped.

PHYLOGENETIC CONSIDERATIONS.—As established earlier (Figure 27, with supportive character evidence), the genus Physemops is a monophyletic assemblage, with the genus Dagus as its probable sister group. Within Physemops the lineages are arranged cladistically into two species groups, here called the nemorosus and panops groups. Each group comprises three species. The nemorosus group is established by the following character evidence:

15. Color of halter: Generally the halteres are pale colored, usually yellowish, but in species of the nemorosus group the capitellum is black.

16. Ocellar bristles: The presence of a pair of divergent, usually proclinate ocellar bristles is the generalized condition. Their absence, as in this species group, is a derived character.

17. Size of the second and third terga of males: Terga 2–5 of males are normally subequal in length. Males of the nemorosus group, however, have enlarged second and third terga. Frequently the fourth tergum is partially, and the fifth tergum is completely concealed by the enlarged third.

18. Vein CuA_1: This vein, along the posterior margin of the discal cell, is generally more-or-less straight. In all members of this group, however, the vein is distinctly bowed posteriorly.

Within the nemorosus group, the three species are related cladistically as indicated in Figure 27. Physemops nemorosus and P. azul are sister species, and these two together form the sister group of P. wheeleri. The monophyly and sister group relationship of nemorosus-azul is established by:

19. Eye vestiture: Of all the species of Dagini, these two are the only ones with microsetulose eyes. The generalized condition is for the eyes to be bare.

20. Size offronto-orbital bristle: The generalized condition is for at least one well-developed, fronto-orbital bristle, subequal with either vertical bristle. In specimens of these two species, the single fronto-orbital is much reduced, not well differentiated from surrounding setulae.

Physemops wheeleri is readily distinguished from its sister group and its monophyly corroborated by:

21. Size of branching aristal rays: In specimens of P. wheeleri, the double row of branching rays is very conspicuous, with the longer rays subequal in length of the width of the third antennal segment. The generalized condition is for the rays to be considerably shorter, less than one-half the width of the third antennal segment and usually much shorter.

The second species group of Physemops, the panops group, appears to have retained more plesiotypic characters, but its monophyly is established by the following synapotypy:

22. Distance between apical scutellar bristles: Generally, the gap separating the apical scutellar bristles is greater than that between the anterolateral scutellar bristle and the apical scutellar bristle on the same side. In species of the panops group, however, the apical scutellar bristles are approximate, with the distance between them distinctly less than that between either apical bristle and the anterolateral scutellar bristle of the same side.

Within the panops group, P. maldonadoi and P. panops are apparently sister species, and together they are the sister group of P. fairchildi. The monophyly and sister group relationship of P. maldonadoi and P. panops are established as follows:

FIGURE 27.—Hypothetical phylogeny for species of genus Physemops (based on character evidence in text).

23. Color of antennal segments: The generalized condition is for at least the basal two segments to be dark, usually black. Frequently the apical one is concolorous, although a pale, usually yellowish third antennal segment, is not uncommon. In specimens of P. maldonadoi and P. panops, however, the entire antenna is yellowish.

24. Vestiture of arista: Generally the aristal vestiture includes one or two rows of very short setula-like rays, usually restricted to the basal one-half to two-thirds. In specimens of these two species, the branching rays are dorsad only, comparatively long, subequal to one-half the width of the third antennal segment, and extend along the basal two-thirds to three-fourths. This combination of features is unique to these two genera.

Physemops fairchildi is readily distinguished from its sister group, and its monophyly is established by the following:

25. Vestiture of face: The generalized condition is for the face to be at least partially tomentose, sometimes thinly so. In specimens of P. fairchildi the face is entirely shiny, devoid of tomentosity, a condition I interpret to be synapotypic.

ZOOGEOGRAPHIC DISTRIBUTION.—New World tropics: West Indies (Puerto Rico and Haiti); Mexico south to Colombia and Ecuador.

DISCUSSION.—Physemops was last revised by Wirth (1970), when five of the six known species were initially described. My treatment of the genus here is to an extent a synopsis of Wirth's study, particularly the descriptive aspects, although the key, cladistic synthesis, and arrangement of species are newly proposed.

Key to Species of Physemops

The nemorosus Group

DIAGNOSIS.—Specimens of this group are similar to those of the panops group but may be distinguished by the following combination of characters: ocellar bristles lacking; arista long, over twice combined length of first 2 antennal segments; capitellum of halter black; vein CuA_1 along posterior margin of discal cell bowed posteriorly; vein R2+3 curved posteriorly apically toward vein R4+5; second and third terga enlarged, first, fourth, and fifth terga much less than one-half length of either second or third terga, partially concealed.

3. Physemops azul Wirth

Physemops azul Wirth, 1970:172.

DIAGNOSTIC DESCRIPTION.—Resembling P. nemorosus but differing from it and other congeners as follows: wing length 1.75 mm; third antennal segment, tibiae, and basal tarsomeres pale, yellowish; face iridescent, with bluish to greenish metallic reflections; otherwise body mostly black.

Head: Vestiture of frons and mesonotum very sparse, appearing subshiny, lacking overt sculpturing, with extremely fine rugose markings; posterolateroclinate fronto-orbital bristle weakly developed, barely evident; arista moderately long, at most twice combined length of first 3 antennal segments, with 2 rows of short setula-like rays extending nearly to apex; third antennal segment moderately long, nearly twice length of second; face densely tomentose, tomentum silvery; facial setae uniform in size, lacking pair of porrect setae near dorsum and larger setae along oral margin; eye with microsetulae.

Thorax: Dorsocentral and acrostichal series with anterior setae larger; scutellum broadly rounded, disc with poorly defined lateral margins, anterolateral scutellar bristles short, less than one-half apical pair; costal vein ratio 6.25; vein M ratio 1.7.

TYPE-LOCALITY.—MEXICO. Oaxaca: Valle Nacional.

PRIMARY TYPE MATERIAL.—Holotype female is labeled “Above Valle Nacional Oaxaca, Mex May 15, 1963 [handwritten]/HOLOTYPE Physemops azul W. W. Wirth [red; species name and sex handwritten].” The holotype is glued to the side of a pin, is in excellent condition, and is in the National Museum of Natural History, Smithsonian Institution, USNM 70664.

GEOGRAPHIC DISTRIBUTION.—This species is known only from the type-locality.

REMARKS.—Physemops azul and P. nemorosus are sister species as indicated in Figure 27, with supportive character evidence as listed.

4. Physemops nemorosus (Cresson)

FIGURES 28–41, 84

Psilephydra nemorosa Cresson, 1914:244; 1918:64 [review, figure of head].

Physemops nemorosus.—Cresson, 1934:211 [combination; designated as type-species of Physemops],—Wirth, 1968:20 [catalog of Neotropical species].

DIAGNOSTIC DESCRIPTION.—Resembling P. azul Wirth but differing from it and other congeners as follows: wing length 2.00 mm; body entirely black except for brown eye and ventral portion of face, which is silvery.

Head (Figures 28, 29, 33–38): Vestiture of frons and mesonotum sparsely tomentose, appearing subshiny to shiny, sculpturing fine, finely reticulate rugose; posterolateroclinate fronto-orbital bristle weakly developed, barely evident; arista long, approximately 3 times combined length of first 3 antennal segments, with 2 rows of short setula-like rays extending nearly to apex; third antennal segment short, at most slightly longer than second; face 2–toned, dorsum sparsely tomentose, mostly subshiny, black, ventral half becoming more densely tomentose, silvery; eye with microsetulae; facial setae uniform in size, lacking pair of porrect setae near dorsum and larger setae along oral margin.

FIGURES 28–32.—Physemops nemorosus: 28, head, lateral aspect; 29, same, anterior aspect; 30, thorax, dorsal aspect; 31, epandrium and cercus, lateral aspect; 32, internal male genitalia, lateral aspect.

Thorax (Figures 30, 39–41, 84): Dorsocentral and acrostichal series with anterior setae weakly developed; scutellum broadly rounded, disc with poorly defined lateral margins, anterolateral scutellar bristles small, less than one-half apical pairs; wing (Figure 84); costal vein ratio 4.6; vein M ratio 1.6.

Abdomen (Figures 31, 32): Male terminalia as in Figures 31, 32.

PRIMARY TYPE MATERIAL.—Holotype male is labeled “Juan Vinas 1 V ‘10 [1 May 1910] C[osta] R[ica] P P Calvert/forest brook 2500 ft. alt. at 4 p. m./HoloTYPE 6065 [number handwritten; red]/NEMOROSA Psilephydra [handwritten].” The holotype is double mounted (minute nadel in cardboard base), is in excellent condition, and is in the Academy of Natural Sciences of Philadelphia, ANSP 6065.

NATURAL HISTORY.—Wirth's field notes (16 Jan 1965; pers. comm.) noted that on the island of Dominica, specimens of this species were observed “swarming in spray at waterfall of brook into Layou River.”

GEOGRAPHIC DISTRIBUTION.—Circumcaribbean and South American. Mexico (Oaxaca) south through El Salvador, Honduras, Nicaragua, Costa Rica, and Panama to Ecuador (Chimborazo) and Brazil (São Paulo). Lesser Antilles, Dominica.

REMARKS.—This species and P. azul are sister species (see “Phylogenetic Considerations” under Physemops). They are also the smallest species of the genus.

This is the most widespread species of Physemops, yet despite its distribution and abundance, nothing is known of its natural history or immature stages.

FIGURES 33–41.—Physemops nemorosus: 33, head, lateral aspect; 34, same, dorsal aspect of left side; 35, ocelli, dorsal aspect; 36, antenna, anterior aspect; 37, compound eye with sensory setae; 38, same, enlargement; 39, notopleuron and bristles, lateral aspect; 40, scutellum and bristles, dorsal aspect; 41, midleg, apex of fifth tarsomere, claws, and pulvilli.

5. Physemops wheeleri Wirth

FIGURES 42–49, 85

Physemops wheeleri Wirth, 1970:176.

DIAGNOSTIC DESCRIPTION.—Resembling P. nemorosus (Cresson) and P. azul Wirth but differing from them and other congeners as follows: wing length 2.90 mm; body entirely black except for brownish eye.

Head (Figures 42–47): Vestiture of frons and mesonotum moderately sparse, appearing subshiny to shiny, finely reticulate rugose sculpturing; posterolateroclinate fronto-orbital bristle well developed; arista with 2 rows of pectinate rays, larger rays subequal to length of third antennal segment; third antennal segment short, at most slightly longer than second segment; face with 1 pair of setae inserted just below dorsal margin of facial prominence, divergent, porrect; facial setae along oral margin distinctly longer than other facial setae; eye bare.

FIGURES 42–49.—Physemops wheeleri: 42, head, lateral aspect; 43, same, lateral aspect of dorsum; 44, ocelli, dorsal aspect; 45, antenna, anterior aspect; 46, frons (prefrons), anterior aspect; 47, same, lateral aspect; 48, scutellum, dorsal aspect; 49, midleg, ventral aspect of fifth tarsomere, claws, and pulvilli.

Thorax (Figures 48, 49, 85): Dorsocentral and acrostichal series with anterior setae weak; scutellum broadly rounded, disc poorly defined laterally, anterolateral scutellar setae weak, less than one-half apical pair; wing (Figure 85); costal vein ratio 9.8; vein M ratio 1.8.

TYPE-LOCALITY.—PANAMA. Canal Zone [former]: Las Cruces Trail.

PRIMARY TYPE MATERIAL.—Holotype female is labeled “Las Cruces Trail Canal Zone Feb 1958/ M R Wheeler Collector/ HOLOTYPE Physemops wheeleri W. W. Wirth [red; species name and sex handwritten].” The holotype is double mounted (glued to a paper point), is in excellent condition, and is in the National Museum of Natural History, Smithsonian Institution, USNM 70668.

GEOGRAPHIC DISTRIBUTION.—Panama (several localities) (see Wirth, 1970) south to Ecuador (Santo Domingo de los Colorados).

REMARKS.—Specimens of this species are easily recognized by the double row of long aristal rays.

Although this species is well accommodated in the nemorosus group, as characterized here, it has apparently retained several characters of the generalized ground plan of the genus, some of which are secondarily plesiotypic with regard to the nemorosus group, for example: (1) the single posterolateroclinate fronto-orbital bristle is well developed, and (2) the pair of facial setae inserted just below the dorsal facial prominence that is divergent and porrect. Both characters are used in the generic diagnosis and at the generic level are synapotypies, but within the nemorosus group they are plesiotypic.

The panops Group

DIAGNOSIS.—Specimens of the panops group are similar to those of the nemorosus group but may be distinguished by the following combination of characters: ocellar bristles present, conspicuous; arista moderately long, usually not over twice combined length of first 3 antennal segments; capitellum of halter mostly pale, usually yellowish; vein CuA_1 along posterior margin of discal cell more or less straight, not distinctly bowed posteriorly; vein R2+3 curved anteriorly apically; abdominal terga 2–5 more or less subequal in length.

6. Physemops fairchildi Wirth

Physemops fairchildi Wirth, 1970:173.

DIAGNOSTIC DESCRIPTION.—Resembling P. panops Wirth and P. maldonadoi Wirth but differing from them and other congeners as follows: wing length 2.10 mm; body entirely black except for third antennal segment and basal tarsomeres, which are pale, yellowish, and ventral portion of face, which is whitish.

Head: Posterolateroclinate fronto-orbital bristle well developed; arista relatively short, less than twice combined length of first 3 antennal segments, with setulae restricted to basal one-fourth or less, otherwise bare; third antennal segment normally developed, slightly less than twice length of second segment; dorsum of facial prominence bare, shiny, thereafter ventrally tomentose, tomentum whitish to silvery white; facial setae of uniform size except for distinct pair of divergent, porrect setae inserted just below dorsal margin of facial prominence.

Thorax: Dorsocentral and acrostichal series with anterior setae well developed; mesonotum with finely developed sculpturing, finely reticulate rugose; scutellum moderately acutely rounded, disc triangular, almost as long as wide, anterolateral scutellar bristles large, more than one-half length of apical pair; costal vein ratio 6.6; vein M ratio 1.6.

TYPE-LOCALITY.—PANAMA. Panama Province: Cerro Campana.

PRIMARY TYPE MATERIAL.—Holotype male is labeled “Cerro Campana Rep. Panama July 1967 W. W. Wirth/HOLOTYPE Physemops fairchildi W. W. Wirth [red; species name, sex, and “HO” handwritten].” The holotype is double mounted (minute nadel in a polyporus block), is in excellent condition, and is in the National Museum of Natural History, Smithsonian Institution, USNM 70665.

GEOGRAPHIC DISTRIBUTION.—Panama (type-locality) south to Colombia (vicinity of Bogotá and Medellin).

REMARKS.—Wirth's field notes indicate that the holotype was collected by sweeping over rocks near a small mountainous stream at about 547 m elevation. Specimens from Colombia were collected at high elevations between 2438 and 2652 m.

Physemops fairchildi is apparently the sister group to the stem lineage that gave rise to P. maldonadoi and P. panops. The relationship is as depicted in Figure 27, with supportive character evidence as indicated.

7. Physemops maldonadoi Wirth

FIGURES 50–55, 86

Physemops maldonadoi Wirth, 1970:173.

DIAGNOSTIC DESCRIPTION.—Resembling P. fairchildi Wirth and P. panops Wirth but differing from them and other congeners as follows: wing length 2.34 mm; antennal segments pale, yellowish, tibiae and tarsi pale, yellowish brown to yellowish; face mostly whitish to silvery white; otherwise body mostly black.

Head (Figures 50, 51): Posterolateroclinate fronto-orbital bristle well developed; arista moderately long, but less than twice combined length of first 3 antennal segments, with long setula-like rays on dorsal surface of basal one-half to two-thirds, longest about one-half width of third antennal segment normally developed, slightly less than twice length of second segment; dorsum of facial prominence sparsely tomentose, becoming more densely tomentose ventrally, tomentum whitish to silvery white; facial setae uniform in size except for distinct pair of divergent, porrect setae inserted just below dorsal margin of facial prominence.

Thorax (Figures 52, 86): Dorsocentral and acrostichal series with anterior setae weakly developed; mesonotum with finely developed sculpturing, finely reticulate rugose; scutellum moderately acutely rounded, disc lacking sharp lateral margins, anterolateral scutellar bristles small, less than one-half apical pair; wing (Figure 86); costal vein ratio 3.4; vein M ratio 2.1.

Abdomen (Figures 53–55): Male terminalia as in Figures 53–55.

TYPE-LOCALITY.—PUERTO RICO. Yauco-Lares Road, km 29.

PRIMARY TYPE MATERIAL.—Holotype male is labeled “Yauco-Lares Rd., P[uerto]. R[ico]. Km. 29 Jan. 20, 1954/J. Maldonado [,] S. Medina Colls./HOLOTYPE Physemops maldonadoi W. W. Wirth [red; species name and sex handwritten].” The holotype is double mounted (glued to a paper point), is in excellent condition, and is in the National Museum of Natural History, Smithsonian Institution, USNM 70666.

GEOGRAPHIC DISTRIBUTION.—This species is known only from the type-locality.

REMARKS.—Physemops maldonadoi and P. panops are sister species as indicated in Figure 27, with supportive character evidence as listed.

FIGURES 50–52.—Physemops maldonadoi: 50, head, lateral aspect; 51, same, anterodorsal aspect; 52, thorax, dorsal aspect.

FIGURES 53–55.—Physemops maldonadoi: 53, epandrium and cerci, posterior aspect; 54, same, lateral aspect; 55, internal male genitalia, lateral aspect.

8. Physemops panops Wirth

Physemops panops Wirth, 1970:175.

DIAGNOSTIC DESCRIPTION.—Resembling P. maldonadoi Wirth and P. fairchildi Wirth but differing from them and other congeners as follows: wing length 2.4 mm; antennal segments pale, yellowish; tibiae and tarsi pale, yellowish brown to yellowish, facial prominence yellow with very sparse tomentose vestiture, otherwise body mostly black.

Head: Posterolateroclinate fronto-orbital bristle well developed; arista moderately long, but less than twice combined length of first 3 antennal segments, with long setula-like rays on dorsal surface of basal one-half to two-thirds, longest ray about one-half width of third antennal segment; third antennal segment normally developed, slightly less than twice length of second segment; tomentum of face sparse dorsally, becoming denser ventrally and laterally, tomentum whitish to silvery white; facial setae uniform in size except for distinct pair of divergent, porrect setae inserted just below dorsal margin of facial prominence.

Thorax: Dorsocentral series with anterior setae moderately well developed, acrostichal series weakly developed anteriorly; mesonotum conspicuously sculptured, reticulate rugose, especially evident on scutellum, with iridescent metallic reflections, scutum silvery to faintly golden, scutellum more purplish to bluish; scutellum with lateral margins at basal one-fourth somewhat parallel, then angling inward distinctly for remainder of length to pointed apex, anterolateral scutellum bristles long, more than one-half length of apical pair; costal vein ratio 4.3; vein M ratio 2.0.

TYPE-LOCALITY.—HAITI.

PRIMARY TYPE MATERIAL.—Holotype male is labeled “Haiti W B Heed/Kenscoff 4000 ft/Feb 1956/HOLOTYPE Physemops panops W. W. Wirth [red; species name, sex, and “HO” handwritten].” The holotype is double mounted (glued to a paper point), is in good condition (some setae of the head missing), and is in the National Museum of Natural History, Smithsonian Institution, USNM 70667.

GEOGRAPHIC DISTRIBUTION.—This species is known only from the type-locality.

REMARKS.—Physemops panops and P. maldonadoi are sister species, as indicated in Figure 27, with supportive character evidence as listed.

Genus Dagus Cresson

Dagus Cresson, 1935:345 [type-species: Ephydra rostrata Cresson, by original designation and monotypy].—Wirth, 1968:24 [catalog of Neotropical species].

DIAGNOSIS.—Specimens of Dagus resemble those of Psilephydra, Physemops, and Diedrops but may be distinguished by the following combination of characters: ocellar bristles present, well developed; lateroclinate fronto-orbital bristles 3, anterior bristle smaller, about one-half length of posterior bristles; arista moderately long but not twice length of first 3 antennal segments, very small setulae dorsally on basal two-thirds; third antennal segment nearly twice length of second segment; face with ventral portion distinctly protrudent, uniformly arched vertically and transversely; mostly subshiny, thinly tomentose, becoming more densely tomentose ventrally and laterally; facial setae sparse but with prominent series extending from facial carina to posteroventral angle of face, larger bristles of this series porrect and anaclinate; genal bristle present, conspicuous; prescutellar acrostichal setae usually lacking; anterior scutellar setae small, less than one-half length of posterior pair; dorsocentral bristles stronger postsuturally, but usually with 1 or 2 larger setae at suture or presuturally; posterior one; posterior notopleural bristle inserted at level distinctly above that of anterior bristle; propleuron bare of setulae; sternopleural bristle weakly developed, especially as compared to mesopleural bristle; apex of vein R2+3 well separated from vein R4+5, distance between these two about equal to that between veins R4+5 and M; pulvilli lacking or greatly reduced; tarsal claws comparatively long, straight, oriented anteriorly, frequently held together throughout length.

MALE TERMINALIA.—Epandrium, in posterior view, triangular, abbreviated dorsally, not forming cercal cavity around cerci, ventral angle with median cleft, lateral view of epandrium with dorsal one-third wide, thereafter ventrally narrowing rapidly to form rather narrow apex; cerci placed at dorsal margin of epandrium, lacking cercal cavity; gonite with 2 posterior projections, each bearing 1 or more setae; aedeagal apodeme about twice as long as wide, roughly oval; aedeagus long and slender, length subequal to that of epandrium.

PHYLOGENETIC CONSIDERATIONS.—See “Phylogenetic Considerations” under tribe Dagini and genus Physemops (pages 4 and 11, respectively).

GEOGRAPHIC DISTRIBUTION.—New World tropics between 30° north latitude and 10° south latitude.

DISCUSSION.—When Cresson (1935:345) selected the name “Dagus” for his new genus, he indicated that the name was derived from a Greek word meaning “a puppet.” Cresson's latinized transliteration of the Greek word was unfortunately in error and has caused confusion as to its proper gender. The correct transliteration is “Dagys”, and as such it would be feminine, but “Dagus”, with its masculine termination in the published form is supported by the rules [ICZN, 1964, art. 30 (a)(i)(3)], which state: “If a genus group name is a Greek word latinized with a change of termination, it takes the gender appropriate to that termination.” Consequently, the generic name is to be treated as masculine, and the correct combination of the type-species is Dagusrostratus (Cresson).

9. Dagus rostratus (Cresson)

FIGURES 56–72, 87

Ephydra pygmaea Williston, 1896:402 [preoccupied, Haliday, 1833:174].

Ephydra rostrata Cresson, 1918:66 [new name for E. pygmaea Williston; figure of head].

Dagus rostrata.—Cresson, 1935:346 [designated as type-species of Dagus].

DIAGNOSTIC DESCRIPTION.—As in generic diagnosis but with the following details: length 1.54 to 2.49 mm.

Head (Figures 56, 57, 62–67): Parafrons densely tomentose, appearing as velvety anterior wedges, distinctly contrasting with mesofrons and fronto-orbits; face lacking antennal foveae.

Thorax (Figures 58, 68–72, 87): Acrostichal setae conspicuous, especially posterior pair; apicolateral setae of fourth tarsomere of foreleg not as conspicuous or curved; wing as in Figure 87.

Abdomen (Figures 59–61): Male terminalia as in Figures 59–61.

TYPE-LOCALITY.—WEST INDIES. Saint Vincent: Perseverance Valley.

Primary Type Material.—Lecototype male, herein designated, is labeled “Co-type [disk with yellow border]/Windward side St. Vincent, W[est]. I[ndies]. H. H. Smith./W. Indies 1907–66./1000 feet./Ephydra pygmaea Will [handwritten; two submarginal red borders]/LECTOTYPE Ephydra pygmaea Williston by W. N. Mathis [handwritten; red].” The lectotype is double mounted (minute nadel in cardboard base), is in good condition (the apical segment of the right antenna is missing), and is in the British Museum (Natural History). I have also examined seven other syntypes (1, 6; BMNH), which are here designated as paralectotypes.

FIGURES 56–61.—Dagus rostratus: 56, head, lateral aspect; 57, same, anterior aspect; 58, thorax, dorsal aspect; 59, epandrium and cerci, posterior aspect; 60, same plus internal male genitalia, lateral aspect; 61, internal male genitalia, lateral aspect.

GEOGRAPHIC DISTRIBUTION.—West Indies (Cuba, Dominica, Jamaica, Saint Vincent); Mexico south through Costa Rica (Cartago; Cresson, 1918:66), to Venezuela (Rancho Grande) and Brazil (without specific locality; Cresson, 1935: 346).

REMARKS.—This is a distinctive species and is not likely to be confused with any others of the tribe.

Both Williston (1896) and Cresson (1918) initially placed this species in the genus Ephydra, as it has three fronto-orbital bristles, lacks conspicuous pulvilli, and the tarsal claws are relatively straight and long. The similarity of these characters with those of Ephydra, however, is due to convergence, as was later observed by Cresson (1935), who proposed the genus Dagus to accommodate the species.

FIGURES 62–72.—Dagus rostratus: 62, head, lateral aspect; 63, same, dorsal aspect; 64, same dorsal aspect of left side; 65, tomentosity of mesofrons (sparse) and parafrons (dense), dorsal aspect; 66, ocelli and bristles, dorsal aspect; 67, antenna, lateral aspect; 68, propleuron and mesopleuron, lateral aspect; 69, notopleuron and bristles, lateral aspect; 70, scutellum, dorsal aspect; 71, mesopleuron, sternopleuron, and bristles, lateral aspect; 72, midleg, apex of fifth tarsomere and claws.

Genus Psilephydra Hendel

Psilephydra Hendel, 1914:99 [type-species: Psilephydra cyanoprosopa Hendel, by original designation and monotypy].—Cresson, 1918:63 [diagnosis, subfamilial placement].—Mathis and Wirth, 1976:128 [comparison with Diedrops].—Cogan and Wirth, 1977:338 [catalog of Oriental species].

DIAGNOSIS.—Specimens of Psilephydra are similar to those of Diedrops, Physemops, and Dagus but may be distinguished by the following combination of characters: ocellar bristles present, well developed; orientation of fronto-orbital bristles variable, 1–2, development variable; arista moderately long, length nearly twice combined length of first 3 antennal segments, apex virtually bare of vestiture, basal two-thirds with some dorsal, minute setulae or nearly bare; third antennal segment longer than second, but not twice length of latter; face generally shieldlike, either shallowly and uniformly protrudent over entire height or with lower two-thirds slightly but distinctly more protrudent (best seen in profile); facial setae variable; genal bristle variable; prescutellar acrostichal setae lacking; scutellar bristles with anterior pair smaller, length as compared to apical pair variable; humeral callus either bare of setulae or with 1 setula; notopleural bristles variable; propleuron bare of setulae; sternopleural bristle variable; apices of veins R2+3 and R4+5 normal, distance between them about equal to that between veins R4+5 and M; vestiture of forefemur variable.

MALE TERMINALIA.—Epandrium shieldlike, forming cercal cavity dorsally; surstyli either distinct or apparently fused to ventral margin; gonite in lateral view with ventral and anterior projections, both slender; aedeagal apodeme long and very slender; aedeagus either about as wide as long or longer than wide.

PHYLOGENETIC CONSIDERATIONS.—The characterization of Psilephydra and the evidence used to establish its monophyly are not entirely satisfactory, and I am recognizing the genus as much for convenience as for soundness of phylogenetic or taxonomic evidence. Still I suspect that the two species comprising Psilephydra are closely related and may well represent a monophyletic lineage. As noted earlier, the character evidence to corroborate the monophyly of Psilephydra is based solely on characters of the male genitalia. Moreover, there are other characters, including several external ones, which resemble those of other genera within the tribe, apparently by convergence. Thus, there is considerable margin for reinterpretation of the relationships, and ultimately I was persuaded to recognize the genus, with its present composition, by two factors. First, the male genitalia of both included species are more similar to each other than to others within the tribe; and second, both species are the only known species of the tribe to occur in the Old World, and specifically in the Orient.

Because I am somewhat ambivalent as to the monophyly and cohesiveness of Psilephydra I have not diagrammed the lineage with its two species, although there is an abundance of characters that could be used as evidence to substantiate each species lineage (see key and species diagnoses).

GEOGRAPHIC DISTRIBUTION.—Old World: Japan, Ryukyu Islands, and Taiwan.

DISCUSSION.—Our knowledge of this genus is limited to descriptive taxonomic data and the brief synthesis of phylogenetic relationships presented here. The ecology, natural history, and description of the life-cycle stages are lacking for both species.

Key to Species of Psilephydra

10. Psilephydra cyanoprosopa Hendel

FIGURES 73–78, 88

Psilephydra cyanoprosopa Hendel, 1914:100.—Cogan and Wirth, 1977:338 [catalog of Oriental species].

Psilephydra cyanocephala [sic] Cresson, 1934:211 [misspelling of specific epithet].

DIAGNOSTIC DESCRIPTION.—Resembling P. fluvialis but differing from it as follows: length 2.47 to 3.15 mm.

Head (Figures 73, 74, 79, 80): Frons generally dull, tomentose, brownish, mesofrons with some metallic reflections, greenish blue; fronto-orbital bristles posterolateroclinate, weakly developed, 1–2; arista mostly bare, microsetulae sparse and restricted to basal one-third; face shallowly and evenly protrudent, subshiny to shiny, mostly silvery but with considerable greenish blue reflections; facial setae uniformly small, including those along oral margin, moderately densely distributed, lacking series extending from dorsal facial prominence to posteroventral angle of face; genal bristle lacking.

FIGURES 73–78.—Psilephydra cyanoprosopa: 73, head, lateral aspect; 74, same, anterior aspect; 75, thorax, dorsal aspect; 76, male terminalia, posterior aspect; 77, internal male genitalia, lateral aspect; 78, same, dorsal aspect.

FIGURES 79–83.—Psilephydra fluvialis: 79, head, lateral aspect; 80, same, anterodorsal aspect; 81, thorax, dorsal aspect; 82, internal male genitalia, lateral aspect; 83, same, dorsal aspect.

Thorax (Figures 75, 88): Anterior scutellar bristle slightly longer than one-half length of posterior pair; humeral callus bare of setulae; anterior notopleural bristle weakly developed as compared to posterior one; posterior notopleural bristle inserted at about same level as anterior bristle; sternopleural bristle weakly developed as compared with mesopleural bristle; forefemur with row of short, spinelike setae along posteroventral surface; apicolateral setae of fourth tarsomere of foreleg as on other tarsomere; wing (Figure 88); costal vein ratio 4.72; vein M ratio 1.92.

Abdomen (Figures 76–78): Male terminalia as in Figures 76–78.

TYPE-LOCALITY.—TAIWAN. Hoozan.

FIGURES 84–89.—Wings: 84, Physemops nemorosus; 85, Physemops wheeleri; 86, Physemops maldonadoi; 87, Dagus rostratus; 88, Psilephydra cyanoprosopa; 89, Psilephydra fluvialis.

PRIMARY TYPE MATERIAL.—Lectotype male, here designated, is labeled “Hoozan Formosa H. Sauter, 1911/7. I. [“7” handwritten = (?) 7 Jan]/Psilephydra cyanoprosopa H. det. Hendel [species name handwritten]/Coll. Hendel/LECTOTYPE Psilephydra cyanoprosopa Hendel by W. N. Mathis [red, handwritten].” The lectotype is pinned directly, is in fair condition (some setae missing: dirty), and is in the Naturhistorisches Museum, Vienna. Hendel's original description mentioned 12 syntypes. Of these I have examined the lectotype, a second male (NMW), and a female (ANSP) (here designated as paralectotypes). The remaining nine specimens are presumably in Vienna, although this has not been confirmed.

GEOGRAPHIC DISTRIBUTION.—TAIWAN.

REMARKS.—This is a very distinctive species within Dagini and is not likely to be confused with any other.

11. Psilephydra fluvialis (Miyagi), new combination

FIGURES 79–83, 89

Lamproscatella fluvialis Miyagi, 1977:88.

DIAGNOSTIC DESCRIPTION.—Resembling P. cyanoprosopa but differing from it as follows: length 2.02 to 2.60 mm.

Head (Figures 79, 80): Frons generally with vestiture and coloration similar throughout, very thinly tomentose, subshiny to shiny, parafrons not distinguished; fronto-orbital bristles lateroclinate, well developed, 2; arista with microsetulae along dorsum of basal two-thirds; face shallowly protrudent, although lower two-thirds slightly but distinctly more protrudent, thinly tomentose, especially dorsomedially which is subshiny, with bronzish to greenish blue reflections; facial setae with marginal ones conspicuously larger and with distinct series of larger setae extending from dorsal facial prominence to posteroventral angle of face; genal bristle present, well developed.

Thorax (Figures 81, 89): Anterior scutellar bristle comparatively small, about one-third length of apical pair; humeral callus with 1 setula; anterior notopleural bristle subequal in size to posterior bristle; posterior notopleural bristle inserted at distinctly higher level than anterior bristle; sternopleural bristle fairly strong, subequal to mesopleural bristle; sternopleural bristle fairly strong, subequal to mesopleural bristle; forefemur lacking row of short, spinelike setae along posteroventral surface; apicolateral setae of fourth tarsomere of foreleg stout, curved inward; wing (Figure 89); costal vein ratio of 5.60; vein M ratio 1.65.

Abdomen (Figures 82, 83): Male terminalia as in Figures 82, 83.

TYPE-LOCALITY.—JAPAN. Shikoku Island: Nametoko, Ehime-ken.

PRIMARY TYPE MATERIAL.—Holotype male is apparently labeled “Nametoko Sept. 10 1962/JAPONIA Shikoku I. MIYAGI.” The holotype is double mounted (minute nadel in a paper rectangle) and is in the Entomological Institute, Hokkaido University. I have not examined the holotype but have studied a female paratopotype. The data cited here are presumed to be like those on the holotype specimen.

GEOGRAPHIC DISTRIBUTION.—Japan (Honshu and Shikoku Islands) and the Ryukyu Islands (Okinawa-honto).

REMARKS.—My attempt to determine the identity of this species for a separate study on the Old World Lamproscatella Hendel was the action that prompted this paper. Through the kindness of Dr. I. Miyagi, I was sent a male and female paratype of his new species, and after examining them, I have concluded that they cannot be included in the genus Lamproscatella but are more closely related to Psilephydra and represent a second species of that genus.

Literature Cited

Cogan, B. H.

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Cogan, B. H., and W. W. Wirth

1977.   Family Ephydridae. In M. D. Delfinado and D. E. Hardy, editors, A Catalog of the Diptera of the Oriental Region, Volume III: Suborder Cyclorrhapha (Excluding Division Aschiza), pages 321–339. Honolulu: The University Press of Hawaii.

Cresson, E. T., Jr.

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Dahl, R. G.

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Haliday, A. H.

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ICZN

1964.   International Code of Zoological Nomenclature Adopted by the XV International Congress of Zoology. Pages xx+176. London: International Trust for Zoological Nomenclature.

Mathis, W. N.

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