PROC. ENTOMOL. SOC. WASH. 
106(2), 2004. pp. 249-279 
A REVISION OF THE SHORE-FLY GENUS CRESSONOMYIA ARNAUD 
(DIPTERA: EPHYDRIDAE), WITH COMMENTS ON SPECIES THAT HAVE 
BEEN EXCLUDED 
Wayne N. Mathis and Tadeusz Zatwarnicki 
(WNM) Department of Entomology, NHB 169, P.O. Box 37012, Smithsonian Institu- 
tion, Washington, D.C. 20013-7012, U.S.A. (e-mail: mathis.wayne@nmnh.si.edu); (TZ) 
Museum and Institute of Zoology, Polish Academy of Sciences, ul. Wilcza 64, 00-679 
Warsaw, Poland, and Department of Biosystematics, University of Opole, ul. Oleska 22, 
45-052 Opole, Poland (e-mail: zatwar@uni.opole.pl) 
Abstract. — Five species of the shore-fly genus Cressonomyia Arnaud are revised, in- 
cluding C. bolivia, n. sp. (Bolivia. La Paz: Tajlihui). The genus is known only from the 
New World tropics and subtropics and is the sister group to Peltopsilopa Cresson. Two 
species groups are recognized, the aciculata group (two species) and the skinneh group 
(three species). Psilopa aeneonigra (Loew). which had been included in Cressonomyia, 
is returned to Psilopa. A neotype is designated for Psilopa aciculata Loew, the senior 
synonym for Plagiops nitidifrons Cresson (new synonym). All species are illustrated and 
distribution maps are also provided. 
Key Words: review, Diptera, Ephydridae, shore flies, Cressonomyia 
This revision treats species of Cresson- since its description, the genus-group no- 
omyia Arnaud, which are known only from menclature was confused for decades be- 
the New World. The species of Cressono- cause of preoccupied names. The generic 
myia have never been treated comprehen- status was first recognized in 1918 as the 
sively, although Cresson (1942, 1946) pro- genus Plagiops Cresson, a preoccupied ge- 
vided a review, including keys, in his treat- nus-group name (Townsend 1911). Cresson 
ments of the Nearctic and Neotropical recognized his nomenclatural lapse and pro- 
shore-fly faunas. The primary objectives of posed the replacement name of Plagiopsis 
this paper are to revise the species and to Cresson, which, unfortunately, was also 
present a phylogenetic context for the genus preoccupied (Brauer and Bergenstamm 
Cressonomyia within the tribe Psilopini 1889). Both Plagiops and Plagiopsis were 
Cresson, subfamily Discomyzinae Acloque. first proposed for tachinid flies, and Arnaud 
We recharacterize Cressonomyia and de- (1958), a specialist on Tachinidae, ultimate- 
scribe and illustrate several characters of ly corrected the nomenclatural oversights 
the male terminalia that have not been re- by suggesting Cressonomyia as the valid, 
ported or analyzed previously. These struc- replacement name. As E. T Cresson, Jr de- 
tures are described and illustrated for all scribed most of the species included in the 
known species and are included in the phy- genus, it is appropriate that the generic 
logenetic analysis. name be a patronym to honor and recognize 
Although the generic concept of Cres- him. The type species for Plagiops is P. 
sonomyia has remained relatively stable nitidifrons Cresson, which automatically 
250 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
became the type species for the replacement 
names. 
Thus far eight names are available for 
species of Cressonomyia (Mathis and Za- 
twarnicki 1995). Loew (1862) described the 
first species, Psilopa aciculata, from spec- 
imens collected in Cuba, and the second 
species, Ephygrobia metallica Schiner 
(1868), was later found to be conspecific 
with C. aciculata (Cresson 1925). Loew 
( 1878) also described the third species, Psi- 
lopa aeneonigra, from specimens collected 
in Texas, and like the first species he 
named, it too became a senior synonym 
when the fourth species, Psilopa fulvipennis 
Hine (1904) from Louisiana, was discov- 
ered to be conspecific with C. aeneonigra 
(Cresson 1942). The correct generic status 
of Psilopa aeneonigra and P. fulvipennis is 
reported in this paper Cresson named the 
other four species, although none was de- 
scribed in Cressonomyia. The four species 
in their original generic combination are: 
Plagiops hinei (Cresson 1922); Psilopa 
meridionalis (Cresson 1918); Plagiops ni- 
tidifrons (Cresson 1918); and Psilopa skin- 
neri (Cresson 1922). Aside from catalog en- 
tries (Wirth 1965, 1968; Mathis and Za- 
twarnicki 1995) and Cresson's synopses 
(1942, 1946), there are no other substantive 
papers on Cressonomyia. 
Cressonomyia has always been associat- 
ed with the genus Psilopa and related gen- 
era, which were usually recognized as the 
tribe Psilopini (Cresson 1942, 1946; Wirth 
1965, 1968; Mathis and Zatwarnicki 1995). 
We continue with that precedent, as all mor- 
phological evidence (see key and diagnosis 
below) substantiates that tribal placement. 
We also adhere to Zatwarnicki's (1992) 
characterization of Psilopini, which ex- 
cludes genera that are more closely related 
to Discomyza Meigen as a separate tribe, 
Discomyzini Acloque. Both Discomyzini 
and Psilopini are tribes in the subfamily 
Discomyzinae (Mathis and Zatwarnicki 
1995). 
Methods and Materials 
The descriptive terminology, with the ex- 
ceptions noted in Mathis (1986) and Mathis 
and Zatwarnicki (1990a), follows that pub- 
lished in the Manned of Nearctic Diptera 
(McAlpine 1981). Because specimens are 
small, usually less than 3.5 mm in length, 
study and illustration of the male terminalia 
required use of a compound microscope. 
We have followed the terminology for most 
structures of the male terminalia that other 
workers in Ephydridae have used (see ref- 
erences in Mathis 1986, and Mathis and Za- 
twarnicki 1990a, b), such as pre- and post- 
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 struc- 
tures of the male terminalia is provided di- 
rectly on Figs. 2-15. The species descrip- 
tions are composite and not based solely on 
the holotypes. One head and two venational 
ratios that are used in the descriptions are 
defined below (all ratios are based on three 
specimens: the largest, smallest, and one 
other). Gena-to-eye ratio is the genal height 
measured at the maximum eye height di- 
vided by the eye height. Costal vein ratio: 
the straight line distance between the apices 
of R2+3 and R4+5/distance between the api- 
ces of Rj and R2+3. M vein ratio: the straight 
line distance along vein M between cross- 
veins (dm-cu and r-m)/distance apicad of 
dm-cu. 
Distribution maps were made using ESRI 
Arc View® GIS 3.2. IvOngitude and latitude 
coordinates were obtained for the locality 
where each specimen was collected and en- 
tered into a Microsoft Excel® spreadsheet. 
If available, the longitude and latitude were 
obtained directly from the specimen labels. 
For specimen labels that did not have lon- 
gitude and latitude, gazetteers and maps 
were used to determine the geographical 
coordinates. The geographic coordinate 
spreadsheet was converted to a tab delim- 
ited text file and imported into ESRI 
ArcView. The specimen locales were plot- 
ted on a world land projection, presented 
within ESRI ArcView layouts and exported 
as encapsulated postscript (EPS) files. 
The phylogenetic analysis was performed 
VOLUME 106, NUMBER 2 
251 
with the assistance of Hennig86®, a com- 
puterized algorithm that produces clado- 
grams by parsimony. Character data were 
polarized primarily using outgroup proce- 
dures. Although autapomorphies were not 
included in the cladistic analysis (they were 
made inactive), which would skew the con- 
sistency and retention indices, we listed 
them on the cladogram and included them 
as part of generic treatments and phyloge- 
netic considerations to document the mono- 
phyly of the lineages, particularly at the 
species-group level. 
Although many specimens for this study 
are in the National Museum of Natural His- 
tory, Smithsonian Institution, Washington, 
D.C. (USNM), we also borrowed and stud- 
ied numerous specimens that are deposited 
in the following museums: 
ANSP Academy of Natural Sciences of 
Philadelphia, Pennsylvania, USA. 
AMNH American Museum of Natural His- 
tory, New York, USA. 
BYU Brigham Young University, Provo, 
Utah, USA. 
CMP Carnegie Museum of Natural His- 
tory, Pittsburgh, Pennsylvania, 
USA. 
INBIO Instituto Nacional de Biodiversi- 
dad, Santo Domingo, Costa Rica. 
MCZ Museum of Comparative Zoology, 
Harvard University, Cambridge, 
Massachusetts. USA. 
MNBL Museo Nacional de Historia Nat- 
ural, La Paz, Bolivia. 
NMW Naturhistorisches Museum, Wien, 
Austria. 
OHSU Ohio State University, Columbus, 
Ohio, USA. 
Systematics 
Tribe Psilopini Cresson 
Psilopini Cresson 1925: 241. Type genus: 
Psilopa Fallen 1823. 
Heringinae Enderlein 1934: 191. Type ge- 
nus: Hehngiwn Enderlein 1934 (= CUm- 
oneunim Becker 1903). 
Clanoneurinae Enderlein 1936: 168. Type 
genus: Clanoneurum Becker 1903. 
Diagnosis. — Head: Fronto-orbital setae 
reclinate and proclinate: reclinate fronto-or- 
bital seta usually inserted behind larger, 
proclinate fronto-orbital seta. Pedicel bear- 
ing a long, spinelike seta near anterodorsal 
margin. Face usually smooth, if finely stri- 
ate the longest facial seta at least as long as 
its distance from opposite seta; medial fa- 
cial area and lower facial margin without 
setae; facial setae inserted in more or less 
vertical series, parallel with parafacial; sub- 
cranial cavity small. 
Thorax: Prescutellar acrostichal setae 
large (subequal to posterior dorsocentral 
seta), inserted widely apart (distance be- 
tween subequal to that between either pre- 
scutellar and the posterior dorsocentral seta 
on the same side) and usually in front of 
intra-alar seta; presutural or sutural dorso- 
central seta inconspicuous or absent. R stem 
vein lacking setulae on dorsum; vein R2+3 
well separated from costal vein; crossvein 
dm-cu nearly straight or shallowly arched, 
not angulate. 
Abdomen: Presurstylus well developed; 
postsurstylus lobate, lacking a postsurstylar 
process; subepandrial plate well developed, 
usually narrow; pregonite moderately well 
developed, usually bearing 2-3 long, apical 
setulae; aedeagus simple, tubular; phalla- 
podeme generally hemispherical to trian- 
gular with a well-developed, extended keel 
in lateral view; ejaculatory apodeme lack- 
ing; hypandrium well developed, usually 
pocketlike. 
Key to New World Genera of 
Psilopini Cresson 
1. Prescutellar acrostichal setae lacking 2 
- Prescutellar acrostichal setae well developed 
3 
2. Only inner vertical seta present. Lateral mar- 
gins of abdomen sharp .... Trimerina Macquart 
- Both inner and outer vertical setae present. 
Lateral margins of abdomen rounded, revolute 
Triinerinoicies Cresson 
3. Vein Ri+i close to costa beyond end of vein 
R,; crossvein dm-cu with sharp angle at middle 
Clanoneurum Becker 
- Vein R,., well separated from costa: crossvein 
dm-cu mostly straight or shallowly arched, not 
angulate 4 
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PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
4. Base of wing blackish, contrasted with remain- 
der of wing; knob of haher blackish brown to 
black 5 
- Base of wing concolorous with rest of wing, 
usually hyaline or very lightly tinged; knob of 
halter whitish to yellowish 6 
5. Scutellum greatly enlarged, extended far over 
and above abdomen Peltopsilopa Cresson 
- Scutellum normally developed, not extended 
far over abdomen Cressonomyia Arnaud 
6. Face with transverse striae 
Leptopsilopa Cresson 
- Face smooth, lacking transverse striae (trans- 
verse striae in Ceropsilopa coqiiilletti Cresson, 
which has entirely yellow legs) 7 
7. Pedicel conical, broader apically, without dor- 
soapical lobe, dorsoapical spine weak (at most 
Vi as long as 1st flagellomere): 1st flagellomere 
from 2-4 X as long as high 
Ceropsilopa Cresson 
- Pedicel short and subtriangular, with dorsoap- 
ical lobe and bearing well-developed dorsoap- 
ical spine (at least half as long as 1st flagello- 
mere); 1st flagellomere at most twice as long 
as high Psilopa Fallen 
Genus Cressonomyia Arnaud 
Plagiops Cresson 1918: 53. Type species: 
Plagiops nitidifrons Cresson 1918, orig- 
inal designation; preoccupied, Townsend 
1911. 
Plagiopsis Cresson 1934: 201 [replacement 
name for Plagiops Cresson; preoccupied, 
Brauer and Bergenstamm 1889]; 1942: 
126-127 [Nearctic fauna]; 1944: 162 
[discussion]; 1946: 158-161 [review of 
Neotropical fauna]. 
Cressonomyia Arnaud 1958: 24 [replace- 
ment name for Plagiopsis Cresson]. — 
Wirth 1965: 743 [Nearctic catalog]; 
1968: 11 [Neotropical catalog]. — Mathis 
and Zatwarnicki 1995: 34-35 [world cat- 
alog]. 
Diagnosis. — Small to moderately small 
shore flies, body length 1.50-2.35 mm; mi- 
crotomentum generally sparse or lacking, 
appearing subshiny to shiny; mostly black 
species. 
Head: Head in lateral view with antenna 
inserted at dorsal Vr, frons conspicuously 
wider than long; fronto-orbital setae recli- 
nate and proclinate but sometimes weakly 
developed; pseudopostocellar setae well de- 
veloped, subequal to outer vertical seta, ori- 
entation mostly proclinate and slightly di- 
vergent; both inner and outer vertical setae 
well developed; vertex acutely creased; 
posterior ocelli situated immediately before 
creased vertex, ocelli forming isosceles tri- 
angle. Antenna with 1st flagellomere longer 
than pedicel; scape not exerted; arista with 
4-8 dorsal rays. Facial vestiture variable, 
surface mostly flat and plain, lacking pits 
and transverse microrugosity or striae; 1 
strong facial seta, mesoclinate; palpus 
black; proboscis normally developed, not 
elongate. 
Thorax: Generally black to deep bluish 
black, microtomentum sparse to lacking; 
supra-alar seta absent; prescutellar acrosti- 
chal seta well developed; scutellum only 
slightly wider than long, disc sparsely se- 
tulose; basal scutellar seta over Vi length of 
apical seta; anepisternum with 2 large setae. 
Wing mostly hyaline to faintly yellowish 
except for blackish base; crossveins not 
darkened; vein R^^, extending normally to 
costal margin, lacking stump vein; R stem 
vein bare of setulae dorsally. Knob of halter 
black. Femora black; forebasitarsus whitish 
yellow to yellow, only apical 1—2 tarso- 
meres blackish. 
Abdomen: Generally bare of microto- 
mentum, shiny, blackish; tergites 3-4 long, 
5th tergite very short and lacking promi- 
nent, dorsally erect setae along posterior 
margin. Male terminalia: epandrium in pos- 
terior view an inverted, rounded U (open 
ventrally), in lateral view wider subventral- 
ly; cerci lunate to rodlike, narrower dorsal- 
ly, sometimes with a mediodorsal point; 
presurstylus much longer than wide, bear- 
ing 2—3 setae anterobasally; postsurstylus 
longer than wide, generally as an inverted 
L, directed anteroventrally or ventrally, 
with variously developed medial lobes or 
processes; subepandrial plate wider than 
long, usually narrowed medially and with 
each lateral extension slightly enlarged; 
pregonite bearing 3 long setulae; aedeagus 
longer than wide, wider basally in ventral 
view, in lateral view with distal portion di- 
rected posteroventrally, posteroapical mar- 
VOLUME 106, NUMBER 2 
253 
C. skinneri 
Fig. 1 . Cladogram depicting hypothetical cladistic relationships among species of Cressonomyia. 
gin irregular, sometimes with a subapical 
process dorsally; phallapodeme in lateral 
view more or less triangular, keel some- 
times irregular, asymmetrical; hypandrium 
U-shaped, membranous from posterior mar- 
gin to center, in lateral view shallow to 
moderately deep, pocketlike. 
Discussion. — Cressonomyia is similar 
and evidently closely related to Peltopsilo- 
pa. Both genera share at least two synapo- 
morphies: 1. base of wing darkened; 2. 
knob of halter blackish brown to black; and 
3. postsurstylus angulate, L-shaped. Peltop- 
silopa differs from Cressonomyia in having 
a greatly enlarged scutellum that extends 
posteriorly over most of the abdomen. Both 
genera are also only known from the New 
World, especially tropical areas. Although 
Peltopsilopa is distinctive and readily dis- 
tinguished because of the enlarged scutel- 
lum and the setulose gonite (bearing setulae 
in addition to the three long, apical setulae), 
it should perhaps be recognized as a derived 
but included lineage within Cressonomyia. 
Excluded from the genus, based on evi- 
dence accumulated in this study, are Psi- 
lopa aeneonigra, including its junior syno- 
nym Psilopa fulvipennis, which Wirth 
(1965) transferred from Psilopa to Cresson- 
omyia without comment. We confirm the 
synonymy of these two names, first sug- 
gested by Cresson (1942), after determining 
that the two holotypes are conspecific. 
Wirth probably made the generic transfer 
on the basis of the slightly darkened wing 
base of P. aeneonigra, similar to Cresson- 
omyia, but which otherwise differs from 
species included in the genus. The knob of 
the halter, for example, is white, not black- 
ish brown to black, as in Cressonomyia, and 
structures of the male terminalia also differ, 
sharing similarities especially in the shape 
of the subepandrial plate, postsurstylus, and 
hypandrium with those of Psilopa. 
Phylogenetic analysis of species. — In the 
presentation on species-level relationships 
that follows, the characters used in the anal- 
ysis are noted first. Each character is im- 
mediately followed by a discussion to ex- 
plain its states and to provide perspective 
and any qualifying comments about that 
character. After presentation of the infor- 
mation on character evidence, an hypothe- 
sis of the cladistic relationships is presented 
and briefly discussed. The cladogram (Fig. 
1) is the primary mode to convey relation- 
ships, and the discussion is to supplement 
the cladogram and is intended only to com- 
plement the latter. In the discussion of char- 
acter data, a "0" indicates the state of the 
outgroup; a "1" or "2" indicates the de- 
rived states. Characters 3, 8, 9, 11, 12, and 
254 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
Table 1 . Matrix of characters and taxa used in the 
cladistic analysis of Cressonomyia (numbers for char- 
acters correspond with those used in the text). 
13, which are autapomorphies for various 
species, were made inactive (J) for the anal- 
ysis so that they do not tigure into the cal- 
culation of the consistency index. The num- 
bers used for characters in the presentation 
are the same as those on the cladogram, and 
the sequence is the same as noted in the 
character matrix (Table 1). The genus Psi- 
lopa, which is the nominate genus for the 
tribe Psilopini, was the outgroup in our 
phylogenetic analysis. 
Characters Used in the Phylogenetic 
Analysis 
(running count in parenthesis) 
Head: 
1(1). 
Size of fronto-orbital setae: (0) com- 
paratively large, well developed; (1) 
minute (a synapomorphy for the aci- 
culata group). 
2(2). Plane of face and frons: (0) face and 
frons forming an obtuse angle in lat- 
eral view; (1) face and frons nearly 
flat in lateral view, largely bare, shiny 
(a synapomorphy for the aciculata 
group). 
3(3). Number of aristal rays: (0) arista 
bearing 8 dorsal rays; ( 1 ) arista bear- 
ing 4-5 dorsal rays (an autapomorphy 
for the meridionalis group). 
4(4). Face: (0) polished or smooth; (1) 
bearing microtomentum as a vertical 
stripe or more generally microsculp- 
tured (a synapomorphy for the hinei 
group). 
5(5). Height of face: (0) face long, height 
twice that of frons; (1) face shorter, 
height 1.5X that of frons (a synapo- 
morphy for hinei and meridionalis 
groups). 
Thorax: 
1(6). Coloration of basal portion of wing: 
(0) wing completely unicolorous; (1) 
darkened portion limited, at most oc- 
cupying basal Va of cell cua, (a syn- 
apomorphy for Cressonomyia and 
Peltopsilopa); (2) darkened base 
more extensive, occupying y3-y2 base 
of cell cua, (a synapomorphy for the 
aciculata group). 
2(7). Color of knob of halter: (0) whitish 
to yellowish; ( 1 ) brown to blackish 
brown (a synapomoiphy for Cresson- 
omyia and Peltopsilopa). 
3(8). Size of scutellum: (0) normally de- 
veloped, trapedoidal or triangular; ( 1 ) 
greatly enlarged, extended over much 
of abdomen, beetlelike (an autapo- 
morphy for Peltopsilopa). 
Abdomen: 
1(9). Shape of the presurstylus: (0) lobate, 
forming subbasal notch, 3 setulae in 
notch along basomedial portion; (1) 
presurstylus elongate, narrow, almost 
parallel sided, shallowly curved, and 
lacking medial notch and setulae (an 
autapomorphy for the meridionalis 
group). 
2(10). Shape of postsurstylus: (0) with a shal- 
low or very short spur; ( 1 ) with an 
elongate, narrow spur (a synapomor- 
phy for the hinei group). 
3(11). Shape of phallapodeme: (0) triangular, 
with a moderately long projection or 
projection lacking; ( 1 ) with an elon- 
gate anteroventral projection (an au- 
tapomorphy for the meridionalis 
group). 
4(12). Shape of gonite: (0) nearly as wide as 
long, lobate; (1) gonite slender, much 
longer than wide (Figs. 67-68; an au- 
tapomorphy for the meridionalis 
group). 
VOLUME 106, NUMBER 2 
255 
5(13). Shape of hypandrium: (0) usually 
pocketlike in lateral view; (1) hypan- 
drium flattened (an autapomorphy for 
the meridionalis group). 
Using the implicit enumeration (ie*) op- 
tion of Hennig86, which is an exhaustive 
search, a single most parsimonious tree was 
generated from the analysis of the 13 char- 
acters. The cladogram has a length of eight 
steps and consistency and retention indices 
of 1.0. 
As indicated on the cladogram (Fig. 1 ), 
the genus Cressonomyia is divided into 
three basal sublineages to which we have 
accorded species-group status. The first 
basal sublineage comprises the aciculata 
group, which includes C. acuculata and a 
new species, C. bolivia, and its monophyly 
is established by characters 1, 2, and 6. The 
second species group, which is sister group 
to the third (supported by character 5), is 
the hiiiei group and includes C. hinei and 
C. skinneri. The monophyly of the hinei 
group is established by the long, narrow 
spur on the postsurstylus (character 10; 
Figs. 43, 57) and the microtomentose or mi- 
crosculptured face (character 4). The last 
lineage, the meridionalis group, is mono- 
typic, and its monophyly is well corrobo- 
rated by five characters that we have iden- 
tified (characters 3, 9, 11, 12, and 13). 
Key Species of Cressonomyia Arnaud 
AND Other Species that have been 
Included 
1. Knob of halter white to yellowish (genus Psi- 
lopa) Psilopa aeneonigra Loew 
- Knob of halter blackish brown to black (genus 
Cressonomyia) 2 
2. Pronto-orbital setae minute; face and frons 
nearly flat in lateral view, largely bare, shiny; 
face long, height twice that of frons; darkened 
base of wing more extensive, occupying Vi—Vi 
base of ceil cua, 3 
- Pronto-orbital setae well developed; face short- 
er, height 1.5X that of frons; vestiture of face 
and frons variable; darkened base of wing less 
extensive, at most occupying basal Va of cell 
cua, 4 
3. Mesonotum smooth, polished, at most weakly 
aciculate; scutellum arched 
C. bolivia, new species 
- Mesonotum microsculptured. subopaque, gran- 
ulose, or aciculate; scutellum flat 
C aciculata (Loew) 
4. Face and mesonotum microsculptured .... 
C. hinei (Cresson) 
- Pace and mesonotum smooth, shiny or slightly 
microtomentose 5 
5. Face polished; arista with 4-5 dorsal rays . . . 
C. meridionalis (Cresson) 
- Pace with vertical, microtomentose stripe me- 
dially; arista with 8 rays . . C. skinneri (Cresson) 
The aciculata Group 
Remarks. — Of the two species groups we 
recognize in Cressonomyia, the monophyly 
of the aciculata group is more evident. Syn- 
apomorphies that characterize the aciculata 
group and establish its monophyly are (ple- 
siomorphies in parenthesis): (1) fronto-or- 
bital setae minute (elsewhere in Psilopini, 
the fronto-orbital setae are relatively large); 
(2) face and frons nearly flat in lateral view, 
largely bare, shiny (usually the frons and 
face in lateral view are on more angulate 
planes); (3) darkened base of wing more ex- 
tensive, occupying V3—V2 base of cell cua,. 
Having a darkened base is a synapomorphy, 
and we interpret the more extensively dark- 
ened base, as in this species group, to be 
the more derived state in the transformation 
series of this character. 
Cressonomyia aciculata (Loew) 
(Figs. 2-16) 
Psilopa aciculata Loew 1862: 142. — Wil- 
liston 1896: 394 [revision]; 1897: 4 [list, 
Brazil, Grenada, St. Vincent]; 1908: 304 
[figure of wing].— Coquillett 1900: 260 
[fauna. Puerto Rico].— Ragues 1908: 317 
[fauna, Cuba]. — Johnson 1913: 86 [fau- 
na, Florida]; 1919: 447 [fauna. Jamai- 
ca]. — Gowdey 1926: 88 [fauna, Jamai- 
ca]. — Wolcott 1924: 231 [list. Puerto 
Rico]; 1936: 383 [list, Puerto Rico]. 
Plagiops aciculata: Cresson 1 925 : 244 [ge- 
neric combination]. — Curran 1928: 62 
[fauna, Puerto Rico]. 
Plagiopsis aciculata: Cresson 1942: 127 
[generic combination];. 1946: 160-161 
[review. Neotropical fauna, Colombia, 
Costa Rica, Cuba, Guatemala, Haiti, Ja- 
256 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
maica, Mexico, Nicaragua, Panama, 
Puerto Rico, Trinidad, Venezuela]. 
Cressonomyia aciculata: Wirth 1965: 742 
[Nearctic catalog; generic combination]; 
1968: 11 [Neotropical catalog]. — Mathis 
and Zatwarnicki 1995: 34 [world cata- 
log]. 
Ephygrobia metallica Schiner 1868: 242. — 
Cresson 1925: 244 [synonymy, designa- 
tion of a lectotype]. 
Plagiops nitidifrons Cresson 1918: 54. — 
Curran 1928: 32 [fauna, St. Croix].— 
Hendel 1930: 141 [fauna, Paraguay]. 
New synonym. 
Plagiopsis nitidifrons: Cresson 1938: 30 
[generic combination, fauna, Brazil]; 
1946: 159-160 [review. Neotropical fau- 
na, Bolivia, Costa Rica, Guyana, Pana- 
ma]. 
Cressonomyia nitidifrons: Arnaud 1958: 24 
[generic combination]. — Wirth 1968: 11 
[generic combination. Neotropical cata- 
log]. — Mathis and Zatwarnicki 1995: 35 
[world catalog]. 
Description. — This species is distin- 
guished from congeners by the following 
combination of characters: Small to mod- 
erately small shore flies, body length 1 .50- 
2.35 mm. 
Head: Fronto-orbital setae minute. Aris- 
ta bearing 8 dorsal rays. Face and frons in 
lateral view only slightly arched, almost 
straight; face bare, shiny. 
Thorax: Mesonotum microsculptured, 
subopaque, granulose, or aciculate. Wing 
with costal vein ratio 0.87-0.95; M vein ra- 
tio 0.56-0.60. 
Abdomen: Male terminalia (Figs. 2-15): 
Epandrium broadly U-shaped in posterior 
view (Fig. 2), much wider ventrolaterally 
than dorsally; cerci almost rodlike, shallow- 
ly curved (Fig. 2); presurstylus in posterior 
view (Fig. 2) incised medially, forming sub- 
basal notch, 3 setulae in notch, thereafter 
ventrally swollen medially to slightly more 
than width at base then tapered and re- 
curved to fingerlike apex, in lateral view 
wider basally and slightly recurved poste- 
riorly, very gradually tapered to blunt ven- 
tral apex; postsurstylus in lateral view 
(Figs. 5, 15) deeply bilobed, posterior lobe 
longer and wider, width somewhat even 
throughout length, bearing numerous setu- 
lae, posterior margin sinuous, anterior lobe 
shorter, tapered to point; pregonite (Figs. 4- 
5, 10, 13) moderately long, slightly tapered, 
broadly rounded apically, bearing 3 well- 
developed setulae apically; aedeagus in 
ventral view with slight bulge basally, 
thereafter parallel sided on apical half, apex 
broadly rounded, in lateral view with me- 
dial margin broadly incised, apex with 
short, curved, pointed lobe at ventral cor- 
ner; phallapodeme (Figs. 6-7) with keel 
wide basally, extended portion irregularly 
triangular in lateral view; subepandrial plate 
in ventral view (Fig. 11) wider than long, 
narrowed medially, each lateral portion 
slightly flared, in lateral view (Fig. 14) nar- 
rowly triangular, pointed ventrally; hypan- 
drium in lateral view (Figs. 5, 9) more 
deeply pocketlike, in ventral view broadly 
V-shaped (Figs. 4, 8), anteriorly with very 
slender, pointed posterolateral projections. 
Type material. — The neotype male of 
Psilopa aciculata Loew, here designated to 
preserve stability and make more universal 
the use of this name, is labeled "CUBA. 
Holquin: Santa Lucia (3 km N), 22 Feb 
1992, MvonTschimhaus/NEOTYPE S Psi- 
lopa aciculata Loew by Mathis & Zatwar- 
nicki [red]." The neotype is double mount- 
ed (glued to a paper triangle), is in excellent 
condition, and is deposited in the USNM. 
We have designated a neotype for this spe- 
cies because no specimen from the type se- 
ries is available for designation as a lecto- 
type in either the MCZ or the Humboldt 
Universitat (Berlin, Germany) where 
Loew's collections were deposited. There is 
a specimen in the MCZ that is labeled "18 
[handwritten]/Loew Coll./Type? [red; "?" 
handwritten]/Cressonomyia aciculata (Lw,) 
W Wirth '61 [black submargin; handwritten 
except for "WWirth"],"' but this specimen 
does not have the silver square that was 
used to identify Poey's material that Osten 
Sacken acquired and eventually sent to 
Loew (Osten Sacken 1903). The lack of a 
VOLUME 106, NUMBER 2 
257 
cercus 
epandrium 
presurstylus 
(pregonostylus) 
0.1 mm 
Figs. 2-5. Structures of the male terminalia of Cressonomyia aciculata (Cuba. Holgiii'ii: Holguin. north). 2, 
Epandrium, cerci, and presurstylus, posterior view. 3, Same, lateral view. 4, Aedeagus (shaded), phallapodeme, 
postsurstylus, pregonite, and hypandrium, ventral view. 5, Same, lateral view. 
258 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
^^ \ postsuf Stylus 
(postgonostylus) 
Figs. 6—15. Structures of the male termlnalia of Cressoiioinyia aciciilata (Cuba. Holgiti'n: Holguin, north). 6, 
Aedeagus and phallapodeme, ventral view. 7, Same, lateral view. 8. Hypandrium, ventral view. 9. Same, lateral 
view. 10, Pregonite, ventral view. 11, Subepandrial plate, ventral view. 12, Postsurstylus, ventral view. 13, 
Pregonite, lateral view. 14, Subepandrial plate, lateral view. 15, Postsurstylus, lateral view. 
silver square or any other indication that questionable status of this specimen. For 
this was a specimen of the type series is these reasons and to stablize the use of this 
undoubtedly the reason why the red ''Type name, we have selected the male specimen, 
?" was put on this specimen, indicating the as noted, as the neotype. 
VOLUME 106. NUMBER 2 
259 
120° 110° 100° 90° 80° 70° 60° 50° 
Fig. 16. Distribution map for Cressoiioinyia aciculata (dots) and C. holivia (triangles). 
The lectotype female of Ephygrobia me- 
tallica Schiner (designated by Cresson 
1925: 244) is labeled "TYPE [red]/Lindig 
1864 Venezuela/metallica Alte Sammlung/ 
Ephygrobia metallica Schin./Plagiops aci- 
culata (Loew) det. Cresson. 1924." The lec- 
totype is in good condition and is deposited 
in the NMW. 
The holotype male of Plagiops nitidi- 
frons Cresson is labeled "Guacimo 6VI09 
[6 Jun 1909] C[ostalRica PPCalvert/cJ/ 
TYPE 6127 [red; number handwritten]/ 
TYPE Plagiops nitidifrons E T CRESSON 
JR [red; species name handwritten; 
"TYPE" written on left margin of label]." 
The holotype is double mounted (minuten 
in a thin, rectangular piece of cardboard), is 
in excellent condition, and is deposited in 
the ANSP (6127). The type locality. Gua- 
cimo, is in the province of Limon. 
Other specimens examined. — Nearctic: 
UNITED STATES. Texas. Cameron: Boca 
Chica. R. H. Beamer, C. Michener. J. Ro- 
sen, W. Stephen (1 6\ USNM); Browns- 
ville, 8 Apr 1945, D. E. Hardy (1 9; 
USNM); Harlingen, 9 Mar 1945. D. E. Har- 
dy ( 1 9; USNM). 
Neotropical: BAHAMAS. New Provi- 
dence: Nassau, 28 Jun (2 6.2 9; MCZ). 
BELIZE. Stann Creek: Placentia Lagoon, 
Rum Point, 4-5 Nov 1987, D. and W. N. 
Mathis (3 9; USNM). 
BRAZIL. Distrito Federal: Brasilia, 
Lago Paranoa, 4-5 Oct 1974, L. Knutson 
(19; USNM). Rio de Janeiro: Rio de Ja- 
neiro, 3 Aug-Sep 1934, 1939, H. Souza 
Lopes (1 d, 2 9; ANSP). 
COLOMBIA. Magdalena: Aracataca 
(10°35.5'N, 74°1 1.5'W), Feb 1912, Ujhelyi 
(19; ANSP). 
COSTA RICA. Alajuela: Alajuela (945 
m), 15 Sep 1909, R R Calvert (1 cJ; ANSP); 
260 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
Cano Negro (10°53.6'N, 84°47.4'W; 20 m), 
14-27 Apr 1994, K. F. Flores (2 S, 3 9; 
INBIO); Chomogo area (10°18'N, 84°47'W; 
1620 m), 13 Jun 1973, T. L. Erwin, G. F. 
Hevel (1 <?, 1 9; USNM). Cartago: Peralta 
(9°58'N, 83°37'W; 332 m), 7 Aug 1909, P. 
P. Calvert {\ S; ANSP). Gucmacaste: Ha- 
cha, Finca el Oro (5 km S de Hacienda Ale- 
mania; 11°01.4'N, 85°27.5'W; 400 m), 14- 
19 Apr 2002, D. Briceiio (8 S, 11 9; IN- 
BIO); Pitilla (9 km S Santa Cecilia; 
10°59.5'N, 85°25.8'W; 700 m), Feb-7 Apr 
1989, 1993, P Rios (6 6, 8 9; INBIO). 
Heredia: Finca Naranja Valenciana (2 km 
S Pueblo Nuevo, Sarapiqui; 10°28'N, 
84°07'W; 90 m), 31 Jan 1993, M. Ortiz (2 
9; INBIO); La Virgen de Sarapiquf 
(10°23.7'N, 84°08.5'W), 9-24 Apr 1993, 
M. Ortiz (1 9; INBIO); Santo Domingo, 
INBio Parque (9°58.4'N, 84°5.6'W), 18 Feb 
2003, W. N. Mathis (1 d, 1 9; USNM). 
Limon: Batan, 16 Jun 1951, L. L. Cart- 
wright (Id; USNM); Guacimo (10°13'N, 
83°41'W; 110 m), 6 Jun 1909, P P Calvert 
(1 6; paratype; ANSP). Pimtarenas: Esta- 
cion Agujas (8°32.2'N, 83°25.5'W; 300 m), 
19-24 Mar 1997, A. Azofeifa (1 9 ; IN- 
BIO); Estacidn Cabuya (9°35.3'N, 
85°05.9'W; 50 m), 22 Mar 1997. F Alva- 
rado (1 9; INBIO); Estacidn Carara 
(9°46.5'N, 84°31.6'W; 200 m), Feb 1990. 
R. Zufiiga (I 6, 2 9; INBIO); Estacidn 
Quebrada Bonita (9°46'N, 84°36.5'W; 50 
m), 21 Mar-21 Apr, 1989, R. Zufiiga (1 cJ, 
1 9; INBIO); Estacidn Sirena, Corcovado 
(8°28.8'N, 83°35.5'W), 21 Mar-21 Apr 
1992, Z. Fuentes (1 9; INBIO); Montev- 
erde, 26 Mar 1987, W. E. Steiner (13 6,2\ 
9; USNM); Rancho Quemado (8°40.8'N, 
83°34'W; 200 m), Apr 1992, K. Flores (1 
9; INBIO). San Jose: La Caja (8 km W 
San Jose), 28 Apr, H. Schmidt (2 9; 
USNM); Pedregoso (9°22'N, 83°43'W), D. 
L. Rounds (19; ANSP). 
CUBA. Camaguay: Camagiiay, 3 Dec 
1917, J. V. McGuire (1 6\ USNM). Cien- 
fuegos: Soledad, Jardin Botanico (22°7.5'N, 
80°19.2'W), Jan-13 Dec 1927, 1994, C. T. 
Brues. W. N. Mathis. G. Sah (3 S, 6 9; 
MCZ, USNM). Granma: Cayamas, 26 Jan, 
E. A. Schwarz (1 6; USNM). Guantdna- 
mo: Baracoa (30 km SE), 26 Feb 1992, M. 
von Tschirnhaus (1 S\ USNM); Guantana- 
mo, 10 Nov 1914, H. Skinner (1 c?, 4 9; 
ANSP); Pt. Barrios, 3-14 Mar 1905 (19; 
ANSP); San Carlos Est., 4-8 Oct 1913 (1 
S\ ANSP). Havana: Puerto Escondido, 26 
Apr 1983, W. N. Mathis (1 9; USNM). 
Holguin: Holguin, north, Feb 1992, M. von 
Tschirnhaus (3 cJ, 3 9; USNM); Santa Lu- 
cia (3 km N), 22 Feb 1992, M. von Tschirn- 
haus (19; USNM). Isla de Pinos: Mar, C. 
W. Metz (1 6,2 9; MCZ, USNM). Matan- 
zas: Palpite (1 km NE), 2 May 1983, W. N. 
Mathis (1 9; USNM). Oriente: Herradura 
(20°40'N, 76°48'W), C. W. Metz (1 S\ 
MCZ); Santigo de Cuba (20°45'N, 
76°2'W), 23 Feb 1992, M. von Tschirnhaus 
(2 (5,2 9 ; USNM). Pinar del Rio: Soroa 
(2 km NW; 22°48.6'N, 83°1.0'W), 4-5 Dec 
1994, W. N. Mathis (1 9; USNM). Santa 
Clara: Soledad, 1-8 Jun 1939, C. T. Par- 
sons (1 (?, 1 9; MCZ, USNM). 
DOMINICA. Layou River mouth, 9 Jan 
1965, W. W. Wirth (Id; USNM). Spring- 
field Plantation, 18-22 Jul 1978, G. C. 
Steyskal (2 d, 5 9; USNM). 
DOMINICAN REPUBLIC. Distrito Na- 
cional: Ciudad Trujillo (6 km W; = Santo 
Domingo), 16-20 Dec 1955, J. Maldonado 
Capriles (1 9; USNM). La Vega: El Rio 
(9.5 km E; 19°0.9'N, 70°33.5'W; 980 m), 6 
May 1995 (19; USNM); Rio Camu (3.5 
km NW La Vega; 19°13.7'N, 70°35.2'W; 
100 m), 10 May 1995, W. N. Mathis (2 S, 
10 9; USNM); Valle del Rio, 28 Dec 1955, 
J. Maldonado Capriles (2 9 ; USNM). Ped- 
ernales: Cabo Rojo (23.5 km N; 18°06'N, 
71°38'W; 540 m), 13-19 Jul 1990, L. Mas- 
ner, J. Rawlins, C. Young (19; CMP). 
ECUADOR. Los Rios: Quevedo (40 km 
S). 11 Jul 1975. J. Cohen, Peterson, Thorn- 
dal (1 6\ USNM). 
EL SALVADOR. San Salvador, 14 Jun 
1958, L. J. Bottimer (19; USNM). 
GRENADA. St. Andrew: La Force 
Bridges (12°07.6'N, 61°39.8'W), 19 Sep 
1996, W. N. Mathis (2 9; USNM). 
GUYANA. Georgetown (6°48.6'N. 
58°08.6'W), 20-29 Aug 1997, W. N. Math- 
VOLUME 106, NUMBER 2 
261 
is (1 S; USNM); Georgetown. Atkinson 
Airport Road, 2 Jun 1965, S. M. Gaud, L. 
F. Martorell (19; USNM). Karanambo, Ru- 
pununi River (ox bow; 3°45.rN, 
59°18.6'W), 2 Apr 1994, W. N. Mathis (9 
(5, 8 9; USNM). 
HAITI. (1 6, 1 9; USNM). 
HONDURAS. Lancetilla (15°42'N, 
87°28'W), Aug, Stadelmann (19; MCZ). 
JAMAICA. Clarendon: Barnswell Beach 
(17°45.'N, 77°08.5'W), 13 May 1996, D. 
and W. N. Mathis, H. Williams (4 6,4 9; 
USNM); Farquhars Beach (17°50.9'N, 
77°22.8'W), 9 May 1996, D. and W. N. 
Mathis, H. Williams (3 J, 4 9; USNM); 
Jackson Bay (17°44.7'N, 77°12.6'W), 13 
May 1996, D. and W N. Mathis, H. Wil- 
liams (3 6,5 9; USNM); Portland Cottage 
(I7°45.4'N, 77°irW), 13 May 1996, D. 
and W. N. Mathis, H. Williams (1 6,3 9; 
USNM); Portland Cottage (1 km S; 
17°45.8'N, 77°12.6'W), 13 May 1996, D. 
and W. N. Mathis. H. Williams (1 6, 1 9; 
USNM); Salt River (4 km N; 17°52.1'N, 
77°09.5'W), 13 May 1996. D. and W N. 
Mathis, H. Williams (1 9; USNM); Toll 
Gate (7.7 km S; 17°58'N, 77°22.3'W), 9 
May 1996, D. and W. N. Mathis, H. Wil- 
liams (1 d, 1 9; USNM). Manchester: Ba- 
tersea (17°13'N. 77°29'W), Feb 1910. R. 
Thaxter (1 6; ANSP); Mandeville, Feb 
1910, R. Thaxter (19; ANSP); near Man- 
deville (18°03.5'N, 77°31.9'W), 15 Apr-7 
May 1996, 2000, D. and W. N. Mathis, H. 
Williams (12 cJ, 24 9; USNM); near War- 
wick (17°54.rN, 77°25.5'W), 7 May 1996, 
D. and W N. Mathis, H. Williams (1 9 
USNM). St. Andrew: Irishtown (5 mi SW: 
via road). 7 Dec 1975, G. F Hevel (1 6 
USNM); Ferry River, 13 May 1941, E. 
Chapin (1 9; USNM); Hardwar Gap. 10 
Mar 1970, T Farr, W W. Wirth (1 6; 
USNM). St. Catherine: Fresh River at Fer- 
ry, 22 Jul 1962, T. Farr, O. S. Flint (19; 
USNM). St. Elizabeth: Balaclava ( 18°10'N, 
77°39'W), R. Thaxter (19; MCZ); Black 
River (18°01.4'N, 77°51.rW). 11 May 
1996, D. and W. N. Mathis. H. Williams (3 
6, 2 9; USNM); Elim (18°07.rN, 
77°40.5'W), 10 Apr 2000, W N. Mathis (1 
6, 2 9; USNM); Maggotty Falls 
(18°08.2'N, 77°45.rW). 18 Apr 2000, W. 
N. Mathis (19; USNM). 
MEXICO. Chiapas: Boca de Ciela (17 
km S Puerto Arista), 18 May 1985, A. 
Freidberg, W N. Mathis (1 9; USNM); 
Cascadas de Agua Azul (62 km S Pal- 
enque), 7 May 1985, W N. Mathis (l 6 , \ 
9; USNM); Finca Prusia (33 km S Jalten- 
ango; 1.000 m), 10-12 May 1985, W N. 
Mathis (19; USNM); Union Juarez (9 km 
S), 23 Apr 1983 (1 d, 2 9; USNM). Jal- 
isco: Puerto Vallarta, 5 Oct 1984, G. E. Bo- 
hart (2 6; BYU). Tabasco: Teapa (8 km 
SW), 6 May 1985, W N. Mathis (1 9; 
USNM). Veracruz: Ciudad Aleman, 3 May 
1985. W N. Mathis (26,29; USNM); 
Fortin de las Flores, 2 May 1985, W N. 
Mathis (\ 6; USNM); Ocotal Chico (600 
m), 4-5 May 1985, W. N. Mathis {\ 6; 
USNM). 
MONTSERRAT. Trinidad, 29 Jun 1905, 
A. Busck (19; USNM). 
PANAMA. Canal Zone: Coraza, 1-6 
Mar 1911, A. Busck (1 6, 1 9; ANSP); 
Paraiso, 3-7 Feb 1911, A. Busck (1 c?, 2 
9; ANSP); Plantation "BoiTacho," 10 Jul 
1918, H. F Dietz, J. Zetek (19; USNM). 
PARAGUAY. Asuncion, May 1905, Ve- 
zenyi (1 6, 2 9; ANSP). Villarica, Jul 
1937, F Schade (3 6,3 9; USNM). 
PERU. Madre de Dios: Manu, Rio 
Manu. near Romero, 8 Sep 1988, W N. 
Mathis (1 6.3 9; USNM). 
PUERTO RICO. Aguadilla, Jan 1899, A. 
Busck (2 9; USNM). Arecibo (beach; 
18°28.7'N, 66°42'W), 23 Sep 1995, D. and 
W. N. Mathis (2 9; USNM). Arroyo, Feb 
1899, A. Busck (1 9; USNM). Guanica 
(18°N, 66°54'W; Santa Rita), 12 May 1965, 
S. M. Gaud (5 9; USNM). Henry Bks, 19 
Nov 1952, E S. Blanton (2 9; USNM). Ma- 
yaguez, 21-23 Jun 1915 (1 9; ANSP). Pla- 
ya de Guayanilla ( 1 8°0.4'N, 66°46. 1 'W), 19 
Sep 1995, D. and W N. Mathis (2 9; 
USNM). Utuado. Jan 1899. A. Busck (1 9; 
USNM). Yabucoa (18°03'N. 65°52'W). 14 
May 1965, S. M. Gaud (1 .9; USNM). 
ST. VINCENT. St. Andrew: Buccament 
Bay (near beach; 13°1 1 'N, 61°16'W), 8 Jun 
262 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
1991, D. and W. N. Mathis (19; USNM). 
St. Patrick: Cumberland Bay (near beach; 
13°16'N, 61°16'W), 28 Mar-10 Jun 1989, 
1991, D. and W. N. Mathis (2 6,2 9; 
USNM). 
TOBAGO. St. John: Charlotteville 
(beach; 11°19.5'N, 60°32.9'W), 16-18 Apr 
1994, D. and W. N. Mathis (1 J; USNM). 
Charlotteville (5 km S; 1 1°19'N, 60°34'W), 
Hermitage River and beach, 22 Apr- 10 Jun 
1993, 1994, W. N. Mathis (2 6, 5 9; 
USNM); Parlatuvier (creek; 1 1°17.9'N, 
60°35'W), 20 Apr 1994, W. N. Mathis (2 
(?, 4 9; USNM); Speyside (1 km NW; Doc- 
tor River; in8'N, 60°32'W), 12-13 Jun 
1993, W. N. Mathis (3 6,4 9; USNM). St. 
Paul: Argyle Falls (11°15'N, 60°35'W), 21 
Apr 1994, W. N. Mathis (5 6. 4 9; 
USNM); Delaford, Kings Bay (iri6'N, 
60°32.8'W), 13 Jun 1993, W. N. Mathis (2 
d, 4 9 ; USNM); Roxborough (6 km NNW; 
11°16'N, 60°35.4'W), 20 Apr 1994, W. N. 
Mathis (7 9; USNM). 
TRINIDAD. St. Andrew: Valencia ( 1 km 
W; 10°39'N, 61°13'W), Aripo River, 20 Jun 
1993, W. N. Mathis {6 6,3 9: USNM). 
VENEZUELA. Aragiia: Maracay (NW at 
km 16), 14 Mar 1982, G. E and J. E Hevel 
(6 6,9 9; USNM). Bolivar: El Miamo (10 
km SW), 20 Mar 1982, G. E and J. E Hevel 
(1 9; USNM); Guasipati (7.6 km SE), 22 
Mar 1982, G. E and J. E Hevel (2 6; 
USNM); Upata (19 km SE), 20 Mar 1982, 
G. E and J. E Hevel (2 9 ; USNM). La Pied- 
rita, 16 Nov 1911, S. Brown (19; ANSP). 
Distribution (Fig. 16). — Nearctic: USA 
(AL?, TX). Neotropical: Bahamas, Belize. 
Brazil (Distrito Federal, Rio de Janeiro), 
Colombia (Magdalena), Costa Rica (Ala- 
juela, Cartago, Guanacaste, Limon, Puntar- 
enas, San Jose), El Salvador, Guyana, Hon- 
duras, Mexico (Chiapas, Jalisco, Tabasco, 
Veracruz), Panama, Paraguay, Peru, Trini- 
dad and Tobago, Venezuela, West Indies 
(Cuba, Dominica, Dominican Republic, 
Grenada, Haiti, Jamaica, Montserrat, Puerto 
Rico, St. Vincent). 
Remarks. — We found considerable intra- 
specific variation in the degree of micro- 
sculpturing of the mesonotum and in the 
convexity of the scutellum of this species. 
Cresson (1946: 159-162) used these char- 
acters to distinguish between C. aciculata 
and his C. nitidifrons. Our attempts to use 
these characters proved futile, given the 
variation, and when we examined structures 
of the male terminalia, we quickly discov- 
ered that these two species are essentially 
identical. Thus, our observations reveal that 
there is intraspecific variation in the mi- 
crosculpturing and scutellar convexity but 
that structures of the male terminalia are 
consistent. Cressononiyia aciculata and C. 
nitidifrons are conspecific, and their names 
are synonyms with the former being senior. 
Although primarily occurring in the Neo- 
tropical Region, we have examined speci- 
mens of this species from southern Texas. 
Cresson (1942) reported a specimen from 
Alabama, which we have not confirmed and 
thus did not include on the distribution map 
of this species (Fig. 16). 
Cressonomyia bolivia Mathis and 
Zatwarnicki, new species 
(Figs. 17-30) 
Description. — This species is distin- 
guished from congeners, especially of the 
aciculata group, by the following combina- 
tion of characters: Small to moderately small 
shore flies, body length 1.50-1.90 mm. 
Head: Fronto-orbital setae minute. Aris- 
ta bearing 8 dorsal rays. Face and Irons in 
lateral view only slightly arched, almost 
straight; face bare, shiny. 
Thorax: Mesonotum microsculptured, 
subopaque, granulose, or aciculate. Wing 
with costal vein ratio 0.97-1.05; M vein ra- 
tio 0.62-0.67. 
Abdomen: Male terminalia (Figs. 17- 
30): Epandrium broadly U-shaped in pos- 
terior view (Fig. 17), much wider ventro- 
laterally than dorsally; cerci almost rodlike 
(Fig. 17). more rounded laterally, medial 
margin nearly straight; presurstylus in pos- 
terior view (Fig. 17) incised medially, form- 
ing subbasal notch, 3 setulae in notch along 
basomedial portion, thereafter ventrally 
swollen medially to slightly less than width 
at base then tapered and recurved to pointed 
VOLUME 106. NUMBER 2 
263 
Figs. 17-20. Structures of the male terminalia of Cressonomyia bolivia (Bolivia. La Pa:: Tajlihui, 15°40.8'S, 
67°41.7"W: 590 m). 17. Epandrium. cerci. and presurstylus. posterior view. 18, Same, lateral view. 19, Aedeagus 
(shaded), phallapodeme, postsurstylus, pregonite, and hypandrium, ventral view. 20, Same, lateral view. 
264 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
apex, in lateral view (Fig. 18) wider basally 
and slightly recurved posteriorly, very 
gradually tapered to blunt ventral apex; 
postsurstylus in lateral view (Figs. 20, 30) 
deeply bilobed, posterior lobe longer and 
wider than anterior lobe, bearing numerous 
setulae, slightly angulate, apex bluntly 
rounded; pregonite (Figs. 19-20, 27, 29) 
moderately long, slightly tapered, broadly 
rounded apically, bearing 3 well-developed 
setulae apically; aedeagus in ventral view 
(Fig. 19) with slight bulge on basal two- 
thirds, lateral margin of swollen portion ir- 
regularly wavy, thereafter apically parallel 
sided, apex broadly rounded, in lateral view 
(Figs. 20, 22) with medial margin deeply 
sinuous, apex irregularly truncate; phalla- 
podeme with keel moderately wide basally, 
extended portion trapezoidal in lateral view; 
subepandrial in lateral view (Fig. 26) ta- 
pered to curved, point; hypandrium in lat- 
eral view moderately deeply pocketlike, in 
ventral view subquadrate anteriorly, wider 
than long, anterior margin nearly flat, with 
wide posterolateral projections posteriorly, 
lacking anterior projections. 
Type material. — The holotype male is la- 
beled "BOLIVIA. Depto. La Paz[,] Tajli- 
hui, 590 m[,] 15°40.8'S 67°41.7'W[,] 12-iii- 
2001 [12 Mar 2001], S.D. Gaimari/HO- 
LOTYPE Cressonomyia bolivia 6 W.N. 
Mathis USNM & Zatwarnicki [red; species 
name and "& Zatwarnicki" handwritten]." 
The holotype is double mounted (minuten 
in a block of plastic), is in excellent con- 
dition, and is deposited in the MNBL. 
Twenty-six paratypes (14 J, 12 9; MNBL, 
USNM) bear the same locality label data as 
the holotype. 
Other specimens examined. — Neotropi- 
cal: BOLIVIA. La Paz: Guanay (15°29.8'S, 
67°52.7'W; 460 m), 13 Mar 2001, W. N. 
Mathis (1 (5; USNM); Guanay (3 km E; 
15°30.2'S, 67°52.3'W; 500 m), 14 Mar 
2001, W. N. Mathis (2 9; USNM). 
Distribution (Fig. 16). — Neotropical: Bo- 
livia (La Paz). 
Etymology. — The species epithet, boli- 
via, alludes to the country where the type 
series was collected. 
Remarks. — Although this species is now 
only known from Bolivia, we would expect 
that it will be found elsewhere at mid-ele- 
vational sites. 
The hinei Group 
Remarks. — The hinei group, which com- 
prises C. hinei and C. skinneri, is distin- 
guished from the aciculata group or meri- 
dionalis groups by the following combina- 
tion of characters (synapomorphies that 
characterize the meridionalis group and es- 
tablish its monophyly are indicated by an 
*): (1) fronto-orbital setae well developed; 
(2*) face shorter, height 1.5X that of frons; 
vestiture of face and frons variable; (3*) 
face microsculptured or with vertical micro- 
tomentose stripe; (4) darkened base of wing 
less extensive, at most occupying basal Va 
of cell cua,; and (5*) postsurstylus with a 
posterior lobe that is elongate, narrow, spur- 
like (Figs. 43, 57). 
Cressonomyia hinei (Cresson) 
(Figs. 31-45) 
Plagiops hinei Cresson 1922: 135. 
Plagiopsis hinei: Cresson 1942: 127 [ge- 
neric combination]; 1944: 162 [correc- 
tion of lapsus calami in 1942: 127]; 1946: 
159 [review. Neotropical fauna]. 
Psilopa hinei: Cresson 1942: 127 [generic 
combination; lapsus calami]. 
Cressonomyia hinei: Wirth 1965: 742 [Ne- 
arctic catalog; generic combination]. 
Description. — This species is distin- 
guished from congeners, especially of the 
skinneri group, by the following combina- 
tion of characters: Small to moderately 
small shore flies, body length, 1.75-2.35 
mm. 
Head: Fronto-orbital setae well devel- 
oped. Arista bearing 7-8 dorsal rays. Face 
and frons moderately arched in lateral view; 
face short, height 1.5X that of frons, mod- 
erately microsculptured with some irides- 
cent greenish blue coloration. 
Thorax: Mesonotum moderately micro- 
scuptured; darkened base of wing at most 
occupying basal V4 of cell cua,. Wing with 
VOLUME 106, NUMBER 2 
265 
Figs. 21-30. Structures of the male terminalia of Cressonomyia bolivia (Bolivia. La Paz: Tajlihui, 15°40.8'S. 
67°41.7'W; 590 m). 21, Aedeagus and phallapodeme, ventral view. 22, Same, lateral view. 23, Hypandrium, 
ventral view. 24, Same, lateral view. 25, Subepandrial plate, ventral view. 26, Same, lateral view. 27, Pregonite, 
ventral view. 28, Postsurstylus, ventral view. 29, Pregonite, lateral view. 30, Postsurstylus, lateral view. 
costal vein ratio 0.96-1.10; M vein ratio 
0.62-0.63. 
Abdomen: Male terminalia (Figs. 31- 
44): Epandrium broadly U-shaped in pos- 
terior view (Fig. 31), rounded, moderately 
(Fig. 31) almost rodlike and parallel sided; 
presurstylus in posterior view (Fig. 31) in- 
cised medially, forming a large subbasal 
notch, 3 setulae in dorsal portion of notch, 
thereafter ventrally greatly swollen medi- 
wider ventrolaterally than dorsally; cerci ally to slightly more than width at base then 
266 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
Figs. 31-34. Structures of the male terminalia of Cressoiiaiiiyia tiiiiei (Mexico. Tabasco: Teapa (8 km SW)). 
31, Epandrium, cerci, and presurstylus, posterior view. 32, Same, lateral view. 33, Aedeagus (shaded), phalla- 
podeme, postsurstylus, pregonite. and hypandrium, ventral view. 34, Same, lateral view. 
VOLUME 106, NUMBER 2 
267 
tapered and recurved to short, pronglike 
apex, in lateral view (Fig. 32) wider basally, 
thereafter almost straight, very gradually ta- 
pered to blunt ventral apex; postsurstylus in 
lateral view (Figs. 34. 43) trilobed, medial 
lobe much longer and wider, spatulate on 
apical half, bearing numerous setulae, pos- 
terior margin of spatulate portion with 4-5 
setulae from dentate bases, posterior lobe V3 
length of medial lobe, slender, spurlike, 
bearing 1-2 setulae, anterior lobe very 
short, broadly triangular; pregonite (Figs. 
33-34, 39, 42) moderately long, slightly 
narrowed medially, thereafter widened to 
broadly rounded to truncate apex, bearing 3 
well-developed setulae apically; aedeagus 
in ventral view (Figs. 33, 35) with slight 
bulge on basal third, thereafter apically 
very slightly flared to mostly parallel sided, 
apex broadly truncate, in lateral view al- 
most parallel sided, medial margin very 
shallowly and widely incised at middle 
third; phallapodeme (Figs. 34, 35-36) with 
naiTowly projected, parallel sided keel; sub- 
epandrial plate in ventral view (Fig. 40) 
broadly inverted V-shaped, in lateral view 
(Fig. 44) shallowly bilobed, longer lobe 
slightly tapered, pointed apically; hypan- 
drium in lateral view (Fig. 38) more deeply 
pocketlike, in ventral view (Figs. 33-37) 
with anterior, moderately wide, posteriorly 
curved and pointed processes, posterior 
processes oriented posteriorly. 
Type material. — The holotype female of 
Plagiops hinei Cresson is labeled 
"P[uer]t[o].Barrios. Guatemala Mch.3-14' 
05 [3-14 Mar 1905]/Holo-TYPE Plagiops 
HINEI E. T Cresson Jr [maroon; species 
name handwritten].'' The holotype is dou- 
ble mounted (glued to a nanow, paper tri- 
angle), is in excellent condition, and is de- 
posited in OHSU. 
Other specimens examined. — Nearctic: 
UNITED STATES. Florida. Alachua: 10 
Mar 1955, H. V. Weems, Jr. (1 (5, 4 9; 
USNM); Gainesville, 23 Feb 1918, J. M. 
Aldrich (5 9; ANSR USNM). Broward: 
Fort Lauderdale, 26 Jan 1933. A. L. Melan- 
der (2 d, 5 9; ANSP USNM); Hammond- 
ville (26°14'N, 80°12'W), 2 Jun 1953, M. 
R. Wheeler (2 9; USNM). Dade: Royal 
Palm Park, 22 Apr 1930, A. L. Melander 
(19; ANSP). Hendry: 7 Dec 1955, R. A. 
Morse (2 9; USNM). Henry: Clewiston, 20 
Jan 1938, A. L. Melander {\ 6\ USNM). 
Highlands: Highlands Hammock State 
Park, 31 Mar 1956. H. V. Weems, Jr. (1 S\ 
USNM); Sebring, 25 Nov 1954. H. V. 
Weems, Jr. (1 S\ USNM). Miami-Dade: 
Paradise Key, 21-28 Feb 1919, H. S. Bar- 
ber, E. A. Schwarz (1 6, 3 9; ANSR 
USNM). Okeechobee: Okeechobee, 25 Jun 
1953 (1 9; USNM). Orange: Orlando. 18 
Feb-18 Apr 1918, 1956, J. M. Aldrich, W 
W Wirth (6 9; ANSR USNM). Osceola: 
Kissimmee. 1 Feb 1932, A. L. Melander (2 
9; ANSR USNM). Palm Beach: Lake 
Worth, A. T Slosson (I 9; USNM). Sara- 
sota: Sarasota, 2 Mar 1937 (19; USNM). 
Louisiana. Orleans: New Orleans (near). 
1 Jan-23 Feb 1923, 1932. T E Hubbell. A. 
L. Melander (2 9 ; ANSR USNM). 
Mississippi. Hancock: Bay St. Louis, 3 
Sep 1958 (19; USNM). 
South Carolina. Clarendon: Manning. 
29-30 May 1914, W Stone (19; ANSP). 
Texas. Bexar: San Antonio. 3 Apr 1942, 
A. L. Melander (1 9; USNM). Brazoria: 
Angleton. 3 Jan 1946. R. H. Beamer (19; 
USNM). 
Neotropical: BELIZE. Stann Creek: Pla- 
centia Lagoon, Rum Point. 4-5 Nov 1987, 
D. and W N. Mathis (2 9; USNM). 
COSTA RICA. Alajuela: Cafio Negro 
(10°53.6'N, 84°47.4'W; 20 m). 14-27 Apr 
1994. K. F Flores (2 c5. 3 9; INBIO). 
EL SALVADOR. Santa Tecla (12 km 
NW). Feb 1954. W B. Heed (19; USNM). 
MEXICO. Tabasco: Teapa (8 km SW). 6 
May 1985, W. N. Mathis (11 6. 20 9; 
USNM). Veracruz: Ciudad Aleman. 3 May 
1985, W. N. Mathis (2 c?, 2 9; USNM); 
Tampico, 29 Dec 1908 (1 9; ANSP). 
PANAMA. Canal Zone: Coraza. 1 Mar 
1911. A. Busck (1 9; USNM). Panama: 
Tocumen. 13 Feb-25 May 1952. 1953. E S. 
Blanton (4 9; USNM). 
Distribution (Fig. 45). — Nearctic: USA 
(FL. LA, MS, SC, TX). Neotropical: Be- 
lize, Costa Rica (Alajuela), EI Salvador, 
268 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
Figs. 35-44. Structures of the male terminalia of Cressonomyia hinei (Mexico. Tabasco: Teapa (8 km SW)). 
35. Aedeagus and phallapodeme, ventral view. 36, Same, lateral view. 37, Hypandrium, ventral view. 38, Same, 
lateral view. 39, Pregonite, ventral view. 40, Subepandrial plate, ventral view. 41, Postsurstylus, ventral view. 
42, Pregonite, lateral view. 43, Postsurstylus, lateral view. 44, Subepandrial plate, lateral view. 
Guatemala, Mexico (Tabasco, Veracruz), tion there is primarily confined to the south- 
Panama, eastern United States. 
Remarks. — In North America, this is the The moderately microsculptured face 
most widespread species, but its distribu- with some iridescent greenish blue colora- 
VOLUME 106. NUMBER 2 
269 
100° 9D° 
Fig. 45. Distribution map for Cressonomyia hinei. 
tion distinguishes this species most easily 
from congeners. 
Cressonomyia skinneri (Cresson) 
(Figs. 46-58) 
Psilopa skinneri Cresson 1922: 136. — Wol- 
cott 1936: 383 [list, Puerto Rico]. 
Plagiops skinneri: Cresson 1946: 159 [ge- 
neric combination]. 
Plagiopsis skinneri: Cresson 1942: 126 [ge- 
neric combination]; 1946: 158—159 [re- 
view. Neotropical fauna, Brazil, Cuba, 
Panama. Paraguay. Puerto Rico]. 
Cressonomyia skinneri: Wirth 1965: 742 
[Nearctic catalog; generic combination]; 
1968: 1 1 [Neotropical catalog]. — Mathis 
and Zatwarnicki 1995: 35 [world cata- 
log]. 
Description. — This species is distin- 
guished from congeners, especially of the 
skinneri group, by the following combina- 
tion of characters: Small to moderately 
small shore flies, body length 1.65—2.35 
mm. 
Head: Fronto-orbital setae well devel- 
oped. Arista bearing 8 dorsal rays. Face and 
frons moderately arched in lateral view; 
face short, height 1.5X that of frons, with 
vertical, microtomentose stripe medially; 
facial setae in minute pits. 
Thorax: Mesonotum smooth, shiny; 
darkened base of wing at most occupying 
basal V4 of cell cua,. Wing with costal vein 
ratio 0.70-0.78; M vein ratio 0.64-0.7. Tib- 
ial apices yellowish. 
Abdomen: Male terminalia (Figs. 46- 
57): Epandrium broadly U-shaped in pos- 
terior view (Fig. 46), rounded, moderately 
wider ventrolaterally than dorsally; cerci 
(Fig. 46) almost rodlike, wider ventrally, 
lateral margins rounded, medial margin al- 
most straight; presurstylus in posterior view 
(Fig. 46) incised medially, forming an an- 
gulate, moderately deep subbasal notch, 2 
270 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
I 
0.1 mm 
Figs. 46-49. Structures of the male terminalia of Cressonomyia skinneri (Jamaica. Clarendon: Grantham 
(18°09.3'N, 77°23.8'W; 340 m)). 46. Epandrium, cerci, and presurstylus, posterior view. 47. Same, lateral view. 
48, Aedeagus (shaded), phallapodeme, postsurstylus, pregonite, and hypandrium, ventral view. 49, Same, lateral 
view. 
VOLUME 106, NUMBER 2 
271 
setulae in dorsal portion of notch, thereafter 
ventrally shallowly swollen medially to 
slightly less than width at base then tapered 
and recurved to short, blunt apex, in lateral 
view (Fig. 47) much wider basally, there- 
after almost straight, very slightly tapered 
to blunt apex; postsurstylus in lateral view 
(Figs. 49, 57) somewhat trilobed, medial 
lobe much longer and wider, slightly spat- 
ulate on apical half, bearing numerous se- 
tulae, posterior lobe moderately long, nar- 
row, spurlike, bearing 2 setulae, anterior 
lobe broadly triangular; pregonite (Figs. 
48-49, 52) moderately long, in lateral view 
(Fig. 55) subquadrate, apex truncate, bear- 
ing 3 well-developed setulae apically; ae- 
deagus in ventral view (Figs. 48, 550) with 
basal third slightly swollen, lateral margins 
of swollen portion almost parallel sided, 
subquadrate, thereafter almost parallel sided 
to apex, apex broadly truncate, in lateral 
view (Figs. 49, 51) with medial margin 
widely and moderately deeply and irregu- 
larly incised, external margin more evenly 
arched; phallapodeme (Figs. 48-51) with 
keel wide basally, irregularly and asym- 
metrically projected, projection longest to- 
ward hypandrium; subepandrial plate in 
ventral view (Fig. 53) shallowly and broad- 
ly V-shaped, each arm wider than narrow 
medial portion, in lateral view (Fig. 56) 
subquadrate with apical corners slightly 
produced; hypandrium in lateral view (Fig. 
49) more moderately deeply pocketlike, 
slightly angulate, in ventral view (Figs. 48, 
50) with anterior margin symmetrically and 
shallowly sinuous, moderately wide anteri- 
orly, thereafter posteriorly more or less par- 
allel sided, posterior, subanteriorly with 
very slender, pointed posterolateral projec- 
tions. 
Type material. — The holotype female of 
Psilopa skinneri Cresson is labeled "Guan- 
tanamo Cuba/H. Skinner 10 11 '14 [10 Nov 
1914; "10" handwritten]/(5 [sic, specimen 
is a female]/Holo-TYPE Psilopa skinneri E. 
T. Cresson Jr [red; species name handwrit- 
ten]." The holotype is double mounted 
(minuten in a thin, rectangular piece of 
cardboard), is in fair condition (head miss- 
ing), and is deposited in the ANSP (6346). 
The type locality is in the province of 
Guantanamo. 
Other specimens examined. — Neotropi- 
cal: ARGENTINA. Corrientes: Corrientes, 
23 Feb 1927, R. C. Shannon (1 9; USNM). 
BRAZIL. Scio Paulo: Mongagua 
(24°06'S, 46°37'W), 24 Aug 1961, N. L. H. 
Ki-auss (2 (J, 1 ?; USNM). 
CUBA. Cienfiiegos: Aguada de Pasajero 
(22°23'N, 80°5rW), Feb 1915 (1 c?, 3 9 ; 
USNM); Jardin Botanico (Soledad; 
22°7.5'N, 80°19.2'W), Jan-Feb 1927, C. T 
and B. B. Brues (2 c^, 6 9; USNM). Gran- 
ma: Cayamas, Baker (1 9 ; USNM). Guan- 
tanamo: Guantanamo, 10 Nov 1914, H. 
Skinner (1 9 ; paratype; ANSP). Havana: 
Havana, Baker (IS; ANSP); Ojo de Agua 
(22°54.6'N, 82°29.rW), 8 Dec 1994, W. N. 
Mathis (19; USNM). Pinar del Rio: Soroa 
(22°47.7'N, 83°W). 4-6 Dec 1994, W. N. 
Mathis (1 (5. 1 9; USNM). 
DOMINICAN REPUBLIC. Independen- 
cia: Los Bolos (18°37.8'N, 71°39.2'W; 
1370 m), 24 Mar 1999, W. N. Mathis (4 6. 
17 9; USNM). La Vega: El Rio (9.5 km E; 
19°0.9'N, 70°33.5'W; 980 m). 6-24 May 
1995. 1998, W. N. Mathis (11 J, 4 9; 
USNM); Jarabacoa (1-2 km S; 19°06.9'N, 
70°37'W; 520 m), 8-21 May 1995, 1998, 
W. N. Mathis (5 d, 6 9; USNM); Rio 
Camu (3.5 km NW La Vega; 19°13.7'N, 
70°35.2'W; 100 m), 10 May 1995, W. N. 
Mathis (1 9; USNM). Puerto Plata: Rio 
Camu (14 km E Puerto Plata; 19°11.9'N, 
70°37.4'W), 17 May 1995, W. N. Mathis (3 
6, 1 9; USNM). 
JAMAICA. Clarendon: Grantham 
(18°09.3'N, 77°23.8'W; 340 m), 16 Apr 
2000, W. N. Mathis (4 S, 13 9; USNM). 
Manchester: near Clandon (18°09'N, 
77°28.3'W). 8 May 1996, D. and W. N. 
Mathis, H. Williams (19; USNM). Port- 
land: Berridale (18°06.5'N, 76°20'W), Rio 
Grande River, 25 Apr 2000, W. N. Mathis 
(4 d, 4 9; USNM). St. Andrew: Kingston 
(Fresh River), 24 Feb 1969, W. W. Wirth ( 1 
9; USNM); Mavis Bank (1.7 km E; 
18°02.4'N, 77°39.5'W; 575 m), Yallahs 
River, 21-22 Apr-1 May 2000, W. N. 
272 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
I 
0.1 mm 
Figs. 50-57. Structures of the male terminalia of Cressonomyia skinneri (Jamaica. Clarendon: Grantham 
(18°09.3'N, 77°23.8'W; 340 m)). 50, Aedeagus, phallapodeme, and hypandrium, ventral view. 51, Same, lateral 
view. 52, Pregonite, ventral view. 53, Subepandrial plate, ventral view. 54, Postsurstylus, ventral view. 55, 
Pregonite, lateral view. 56, Subepandrial plate, lateral view. 57, Postsurstylus, lateral view. 
Mathis (13 c?, 11 9; USNM); Mavis Bank 
(4.3 kmSE; 18°01.4'N, 76°38.1 'W; 480 m), 
Yallahs River, 22-23 Apr 2000, W. N. 
Mathis (11 (5, 8 9; USNM); Silver Hill 
Gap (18°05.rN, 76°41.1'W; 920 m), 26 
Apr 2000, W. N. Mathis (2 c?, 1 ?; 
USNM); Wag Water River, 25 Feb 1969, W. 
W. Wirth (19; USNM). St. Maty: Annotto 
Bay (marsh), 25 Feb 1969, W. W. Wirth (3 
9; USNM). 
MEXICO. Chiapas: Cacahoatan (7 km 
N), 22 Apr 1985, W N. Mathis (1 6, 1 9; 
USNM); Union Juarez, 23 Apr 1983, W N. 
Mathis (1 9; USNM). Veracruz: Tampico, 
25 Feb 1972, D. Miller, F Parker (1 6; 
USNM). 
VOLUME 106, NUMBER 2 
273 
110° 100° 90° 80° 70° 
Fig. 58. Distribution map for Cressonomyia skinneri. 
PANAMA. Canal Zone: Balboa, Oct 
1946, N. L. H. Krauss (1 9; USNM). Ta- 
boga Island, 26 Feb 1912, A. Busck (1 c?; 
USNM). 
PUERTO RICO. Barranquitas, 5 Jim 
1961, J. Maldonado (19; USNM). Baya- 
mon, Jan 1899, A. Busck (3 c?, 7 9; 
USNM). Dorado, 22 Nov 1964, S. M. 
Gaud, E. Medina (19; USNM). El Yunque 
(road 191; 1,380 ft), 28 Apr 1965, S. M. 
Gaud (19; USNM). Fajardo, Feb 1899, A. 
Busck (19; USNM). Jayuya (2 km E; Rio 
Saliente; 18°12.8'N, 66°33.9'W), 22 Sep 
1995, D. and W. N. Mathis (2 c?, 1 9; 
USNM). Maricao (4 km WNW; 18°10.7'N, 
66°59.6'W), 21 Sep 1995, D. and W. N. 
Mathis (1 S; USNM). Mayaquez, Jan 1899, 
A. Busck (1 9; USNM). Rio Hoconuco 
(18°7.6'N, 67°2.6'W), 20 Sep 1995, D. and 
W. N. Mathis (3 S; USNM). Rio Piedras 
(18°20'N, 66°3'W), 25 Apr-2 May 1965, S. 
M. Gaud, E. Medina (10 c?, 24 9; USNM). 
Rio Piedras, San Gerardo, 24 Jan 1965, E. 
Medina, R Medina (1 9 ; USNM). Rio Aba- 
jo Forest (road 621; 18°18'N, 66°41'W), 29 
Feb 1965, S. M. Gaud (2 J, 3 9; USNM). 
San German, 23 Dec 1962, P. and P. Span- 
gler (19; USNM). Toa Baja, 5 Apr 1915, 
G. Garb (2 9; ANSP). Utuado. Jan 1899, 
A. Busck (3 d, 7 9; USNM). Vieques Is- 
land, Feb 1899, A. Busck (19; USNM). 
TRINIDAD. Caroni: Caroni (3 km W), 
22 Mar 1985, G. E and J. E Hevel (3 c?, 1 
9; USNM); Chaguanas (near), 22 Mar 
1985, G. E and J. E Hevel (3 S, 13 9; 
USNM). St. Andrew: Valencia (1 km W; 
10°39'N, 61°13'W). Aripo River, 20 Jun 
1993, W. N. Mathis (3 (?, 3 9; USNM). 
VENEZUELA. Santa Rosa: Barinas, Feb 
1943, E Anduze (2 9; USNM). 
Distribution (Fig. 58). — Nearctic: USA 
(FL). Neotropical: Argentina (Corrientes), 
Brazil (Sao Paulo), Mexico (Chiapas, Ve- 
racruz), Panama, Trinidad, Venezuela, West 
274 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
Indies (Cuba, Dominican Republic. Jamai- 
ca, Puerto Rico). 
Remarks. — The vertical, microtomen- 
tose, facial stripe is consistently evident but 
varies in its dimensions, sometimes extend- 
ing dorsally to the ptilinal suture and some- 
times becoming gradually wider basally, to- 
ward the oral margin. 
Although we have not examined any 
specimens of this species from the Nearctic 
Region, Cresson (1942) reported a speci- 
men from Florida. This record needs con- 
firmation and is not included on our distri- 
bution map (Fig. 58). 
The Brazilian (Sao Paulo. Mongagua: 
24°06'S, 46°37'W) and Argentinian (Cor- 
rientes: 27°28'S, 58°50'W) localities are 
disjunct and appear to be outliers (Fig. 58), 
which prompted us to re-examine the spec- 
imens, especially the male from Brazil. We 
dissected this male and confirmed its iden- 
tification, and here suggest that the known 
distribution of this species represents a sam- 
pling artifact. Thus, we predict that with 
better sampling, the known distribution will 
include sites between southeastern Brazil 
and northern Argentina and northern South 
America. The specimen from Paraguay that 
Cresson (1946) listed was not located, but 
if accurately identified, it probably reflects 
the same pattern just noted. 
The MERiDiONALis Group 
Remarks. — The meridionalis group com- 
prises a single species, C. mehdionaUs, 
which is somewhat similar externally to 
species of the hinei group. Structures of the 
male terminalia of this group are the most 
derived and divergent within Cressonomyia 
and are the primary basis for recognizing 
the group. The group is distinguished from 
the aciculata or the hinei groups by the fol- 
lowing combination of characters (synapo- 
morphies that characterize the meridionalis 
group and establish its monophyly are in- 
dicated by an *): (1) fronto-orbital setae 
well developed; (2*) arista with 4-5 dorsal 
rays; (3*) face shorter, height 1.5X that of 
frons; (4*) face polished; (5) darkened base 
of wing less extensive, at most occupying 
basal Va of cell cua,; (6*) presurstylus elon- 
gate, narrow, almost parallel sided, shallow- 
ly curved; (7*) phallapodeme with portion 
that attaches to hypandrlium projected; (8*) 
gonite narrow; and (9*) hypandrium flat- 
tened in lateral view. 
Cressonomyia meridionalis (Cresson) 
(Figs. 59-73) 
Psilopa meridionalis Cresson 1918: 52. 
Plagiopsis meridionalis: Cresson 1946: 158 
[generic combination, review. Neotropi- 
cal fauna]. 
Cressonomyia meridionalis: Wirth 1968: 1 1 
[generic combination. Neotropical cata- 
log]. — Mathis and Zatwarnicki 1995: 35 
[world catalog]. 
Description. — This species is distin- 
guished from congeners, especially of the 
skinneri group, by the following combina- 
tion of characters: Small to moderately 
small shore flies, body length, 1.70—2.25 
mm. 
Head: Fronto-orbital setae well devel- 
oped. Arista bearing 4-5 dorsal rays. Face 
and frons moderately arched in lateral view; 
face short, height 1.5X that of frons, pol- 
ished, shiny. 
Thorax: Mesonotum smooth, shiny; 
darkened base of wing at most occupying 
basal Va of cell cua,. Wing with costal vein 
ratio 0.98-1.0; M vein ratio 0.60-0.62. Tib- 
iae mostly black. 
Abdomen: Male terminalia (Figs. 59- 
72): Epandrium moderately broadly U- 
shaped in posterior view (Fig. 59), much 
wider ventrolaterally than dorsally; cerci 
(Fig. 59) somewhat rodlike, more rounded 
laterally, medial margin shallowly curved, 
pointed mediodorsally; presurstylus in pos- 
terior view sicklelike, gently curved, lack- 
ing medial notch and swelling, very slightly 
and gradually tapered to pointed apex, in 
lateral view as a long, narrow rod, only 
very slightly wider basally, apex slightly 
curved, almost truncate; postsurstylus in 
lateral view (Figs. 60, 72) longer than wide, 
angulate. bearing numerous setulae, at cor- 
ner of angle slightly wider from small, ex- 
VOLUME 106. NUMBER 2 
275 
0.1 mm 
Figs. 59-62. Structures of the male terminal ia of Cressonomyia meridioiuilis (Costa Rica. San Jose: Ri'o 
Savegre, San Gerardo de Dota (9°39.5'N. 83°5rW; 2180 m)). 59, Epandrium, cerci, and presurstylus, posterior 
view. 60, Same, lateral view. 61, Aedeagus (shaded), phallapodeme, postsurstylus, pregonite, and hypandrium, 
ventral view. 62. Same, lateral view. 
276 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
0.1 mm 
Figs. 63-72. Structures of the male terminalia of Cressonomyia meridionalis (Costa Rica. San Jose: Rio 
Savegre, San Gerardo de Dota (9°39.5'N, 83°51'W; 2180 m)). 63, Aedeagus and phallapodeme, ventral view. 
64, Same, lateral view. 65, Hypandrium, ventral view. 66, Same, lateral view. 67, Pregonite, ventral view. 68, 
Subepandrial plate, ventral view. 69, Postsurstylus, ventral view. 70, Pregonite, lateral view. 71, Subepandrial 
plate, lateral view. 72, Postsurstylus, lateral view. 
ternal lobe, apex with 2 small dentate pro- lae apically; aedeagus in ventral view (Figs, 
jections at each corner; pregonite (Figs. 61- 61, 63) almost triangular, base much nar- 
62, 67, 70) moderately long, narrow, apical rower than long, apical extension, like dor- 
half rodlike, parallel sided, narrowly round- sal view of a bicycle seat, apex narrowly 
ed apically, bearing 3 well-developed setu- truncate, in lateral view (Figs. 62, 64) with 
VOLUME 106, NUMBER 2 
277 
20° 
10° 
100° 90° 
Fig. 73. Distribution map for Cressonomyia meridionalis. 
80° 
swelling on basal third, swollen portion ex- 
tended medially, rounded, apical half slight- 
ly tapered, apex shallowly concave; phal- 
lapodeme (Figs. 62-64) comparatively 
large with wide, asymmetrically extended 
keel, longest extension toward hypandrium; 
subepandrial plate in ventral view (Fig. 68) 
much wider than long, each lateral portion 
slightly curved posteriorly, bluntly rounded, 
in lateral view (Fig. 71) slightly tapered to 
rounded apex; hypandrium in lateral view 
(Fig. 62) very shallowly pocketlike, some- 
what flattened, in ventral view (Fig. 61) 
suboval, lacking anterior and posterior pro- 
jections. 
Type material. — The holotype male of 
Psilopa meridionalis Cresson is labeled 
"Cartago 17V'09 [17 May 1909] 
C[osta].Rica PPCalvert/d/TYPE 6126 [red; 
number handwritten]/TYPE Psilopa meri- 
dionalis E T CRESSON JR [red: "TYPE" 
written along left margin of label]."" The 
holotype is double mounted (minuten in a 
thin, rectangular piece of cardboard), is in 
good condition (slightly dusty), and is de- 
posited in the ANSP (6126). The type lo- 
cality, Cartago, is in the province of Car- 
tago. 
Other specimens examined. — Neotropi- 
cal: COSTA RICA. Cartago: Cartago, 17 
May 1909, R R Calvert (1 S, 1 9; para- 
types; ANSP); El Alto, Laguna de Ochom- 
ogo (9°53'N, 83°57'W; 1510 m), 7 Jul 
1909, P R Calvert (19: ANSP); Near Ti- 
erra Blanca (Rfo Toyogres; 9°50'N, 
83°55'W), 6 Apr 1910, P P Calvert (2 6, 
2 9; ANSP); Trinidad (9°41.3'N, 83°54'W; 
2530 m), 29 Jun 2001. A. Freidberg (1 c?; 
USNM). Heredia: Santo Domingo (INBIO 
Parque; 9°58.4'N, 84°05.6'W), 23 Jun 2001, 
W. N. Mathis (2 6\ USNM). San Jose: La 
Caja (8 km W San Jose), 1930, H. Schmidt 
(5 d, 1 9; USNM); Rio Savegre, Cabinas 
de Quetzal (9°33.9'N, 83°48'W; 2,270 m). 
278 
PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON 
7-8 Aug 2001, D. and W. N. Mathis (8 6, 
2 9; USNM); Rio Savegre, San Gerardo de 
Dota (9°39.5'N, 83°51'W; 2,180 m), 7-8 
Aug 2001, D. and W. N. Mathis (22 c?, 8 
2; USNM). 
MEXICO. San Luis de Potosi: Ciudad 
del Maiz (40-50 mi NW), 20 Nov 1948, E. 
S. Ross (19; USNM). 
Distribution (Fig. 73). — Neotropical: 
Costa Rica (Cartago, Heredia, San Jose), 
Mexico (San Luis de Potosi). 
Remarks. — The structures of the male 
terminalia, the presurstylus in particular, are 
quite remarkable and represent a major de- 
parture from other species in Cressono- 
myia. The narrow, almost parallel-sided, 
sickle-shaped presurstylus is quite unique, 
and readily identifies this species. Other- 
wise, however, we did not find this species 
to differ greatly from congeners. 
Acknowledgments 
We gratefully acknowledge the assistance 
and cooperation of many organizations and 
individuals who contributed to the field 
work and production of this paper. To Da- 
vid A. Grimaldi (AMNH), Jon K. Gelhaus 
and Jason D. Weintraub (ANSP), Richard 
W. Baumann (BYU), Chen Young (CPM), 
Manuel Zumbado (INBio), Philip D. Per- 
kins (MCZ). Ruth Contreras-Lichtenberg 
(NMW), Peter W. Kovarik (OHSU), and 
their institutions, who loaned specimens, 
we express our sincere thanks. 
Hollis B. Williams provided technical 
support and produced the maps. For re- 
viewing a draft of this paper, we thank Ste- 
phen D. Gaimari and Allen L. Norrbom. We 
also express thanks to F. C. Thompson who 
advised us on nomenclatural issues and to 
Manuel Zumbado who converted Lambert 
coordinates for the Costan Rican grid sys- 
tem into standard latitude and longitude. In 
1995, 1996, and 1998, field work on the 
West Indies was funded in large measure by 
grants from the Biodiversity Program (Bi- 
otic Surveys and Inventories, BSI), Nation- 
al Museum of Natural History, Smithsonian 
Institution (Lynne R. Parenti, former chair, 
George R. Zug, chair). Field work in Bo- 
livia was also supported by BSI. Field work 
on the West Indies and/or in Bolivia was 
greatly expedited through the able and 
pleasant assistance of N. Dianne Mathis, 
Amnon Freidberg, Stephen D. Gaimari, 
Hollis B. Williams, Kelvin Guerrero, Dan- 
iel E. Perez-Gelabert, and Oliver S. Flint, 
Jr. Field work in Guyana was supported by 
the Smithsonian Institution's Biological Di- 
versity of the Guianas Program (publication 
number 72; Vicki A. Funk, Director; Carol 
L. Kelloff, Coordinator). 
This is contribution number 653 from the 
Caribbean Coral Reef Ecosystems (CCRE), 
Smithsonian Institution. 
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