Transactions of the American Entomological Society 127(1): 5-29, 2001

Mayflies (Ephemeroptera) of the Great Plains. I: Nebraska

W. P. McCafferty

Department of Entomology, Purdue University, West Lafayette, IN 47907

Tom H. Klubertanz - Department of Biological Sciences, University of Wisconsin Rock County, Janesville, WI53546

R. P. Randolph

Department of Entomology, Purdue University, West Lafayette, IN 47907

Arwin V. Provonsha

Department of Entomology, Purdue University, West Lafayette, IN 47907

H. R. Lawson

Division of Science and Mathematics, Chadron State College, Chadron, NE 69337

B. C. Kondratieff

Department of Bioagricultural Sciences and Pest Management, Colorado State Univ., Fort Collins, CO 80523

abstract

A 39 are total of 13 families, genera, and 81 species of Ephemeroptera state reported from the of Nebraska, including the first published state records two are new for families, 13 genera, and 38 species. Also provided 335 county are now records for 65 of the species. known from 60 of the 93 areas Nebraska counties and from all drainage represented in the state. Most are common species of the Nebraska fauna relatively in North America. Notable exceptions include Apobaetis lakota McCafferty, Brachycercus edmundsi B. nasutus Sold?n, Sold?n, Cercobrachys serpentis Sold?n, Leptophlebiagravastella and (Eaton), Paraleptophlebia gregalis (Eaton). Much of the fauna is are psammophilous, being typical of sand-bottomed streams, which predomi nate throughout much of the state. The generally mixed North American of are geographic affinities the Nebraska fauna tabulated, and several species significantly demonstrate their eastern, western, or northern range limits in this north-central plains state. 6 GREAT PLAINS MAYFLIES

BACKGROUND AND DISCUSSION

Nebraska was one of several North American states indicated by McCafferty (2000a) as not having been studied to any significant extent with to its fauna. respect Ephemeroptera Study of the Nebraska mayflies was deemed because the central important of geographic position of the its state, relatively large size (77,227 square miles), and its extensive sand bottomed streams and rivers. the Nebraska fauna Thus, could yield data for important understanding transcontinental ranges of the North as a American fauna well providing better understanding of the poorly known psammophilous mayfly fauna (e.g., see McCafferty 1991). Ratcliffe (1990) provided an excellent physiographic review of this state from the perspective of habitat. Nebraska is primarily prairie with six different short and tall grassland types found throughout most of the state, although much of the prairie is now in cultivation. Pine ridges to the extent of elevation occur in the far western 5,340' portion of the state, and deciduous forest as low as 835' elevation may be found in the in Missouri Valley the extreme southeast. In the western two-thirds of the state are the Nebraska Sand Hills (19,300 square miles), the largest sand dune area in the Western Hemisphere. Streams range from low flow with moderate and mixed springs gradient substrates (e.g., Chadron Creek) to moderately large streams with predominately silt and sand bottoms Elkhorn to low (e.g., River) long, meandering, gradient streams, often ribboned due to considerable draw down for agricultural and seasonal low precipitation, that typically exhibit clean shifting sand substrates Niobrara to (e.g., River) the large Missouri River. Previous to this study, published reports of mayflies from Nebraska with associated record data included only 28 species (Traver 1935, Spieth 1941, Hamilton 1959, Swanson 1967, McCafferty 1975, Bednarik and McCafferty 1979, Kondratieff and Voshell 1984, Moul 1984, Pescador 1985, Provonsha and McCafferty 1985, McCafferty and Waltz 1986, Darrow and Pruess 1989, Provonsha 1990, Harris et al. 1999, Klubertanz and Jones 1999, McCafferty 2000b, Wiersema and McCafferty 2000). Five unpublished theses (Hamilton 1952, Pesek 1974, Carnevalo 1981, Decker 1981, Angle 1987) provided data associated with mayflies in Nebraska. Any reports of species in Nebraska contained in those studies are noted in the present study with respect to those that could be verified with additional records given herein or elsewhere or those that should have been identified with confidence at the time considering the state of taxonomic and available aids. knowledge diagnostic Voucher materials from the Carnevalo and Decker theses, if existent, were not made avail to us able upon request; however, AVP verified several of the species involved at the time of the studies. Several vouchers from the Hamilton that (1952) study had been initially deposited at the University of Utah now at were and reside PERC examined by WPM. Eleven of the 81 species herein remain based on or reported entirely unpublished theses abstracts thereof (Carnevalo and Lunt 1982, Decker and Lunt 1982). Our review of previous reports and study of large collections of Nebraska accumulated us Ephemeroptera variously by for the past W. P. MCCAFFERTY ET AL. 7

have occurrence of 13 39 nearly 25 years, indicated the families, genera, in the state. Reviewed and new data are and 81 mayfly species presented 1 is as a indication of the in the text, and Table provided summary geographic affinities of the Nebraska species. From Table 1, it can be seen or less com that several species find their western, eastern, northern, monly southern distribution limits in Nebraska, and that Nebraska is a area with to the eastern and western North clearly transitional respect American fauna. Of considerable interest is the fact that certain otherwise southwestern species have been found in the Pine Ridge area of far and western Nebraska, for example, Baetis magnus McCafferty and Waltz western bajaensis Allen and Murvosh. Some widespread species, as are also common Ne such Heptagenia elegantula (Eaton) throughout braska but remain unknown east of there. Several eastern and mid western western limits in eastern for species apparently find Nebraska, example, Tricorythodes allectus (Needham) and Stenonemafemoratum (Say), although some of these, such as the latter, occur somewhat farther west in Canada (McCafferty and Randolph 1998). Nebraska serves as a bridge between western eastern for certain such as and populations species Ephemerella inermis Eaton and Stenonema terminatum (Walsh). None of the 81 mayfly are to species endemic Nebraska. vast are common The majority of Nebraska mayflies species through out in America. In their ranges North particular, however, Nebraska has a relatively rich fauna of caenid mayflies (both Caeninae and Homoeoneuria Brachycercinae), long-clawed , Pseudironidae, and - (Oligoneuriidae) all groupings commonly associated with sand sub strates. Generally poorly known and infrequently taken mayflies found in Nebraska include Apobaetis lakota McCafferty, Camelohaetidius waltzi B. nasutus B. McCafferty, Brachycercus edmundsi Sold?n, Sold?n, prudens (McDunnough), Caenis youngi Roemhild, Cercobrachys serpentis Sold?n, Homoeoneuria ammophila (Spieth), Leptophlebia gravastella (Eaton), and Paraleptophlebia gregalis (Eaton). The first two species have only recently been discovered, are small and difficult to collect, and thus it is premature to estimate or environmental status. their potential rarity Species of are Brachycercus and Cercobrachys poorly understood, and thus many are not to no collected specimens identified species, and valid estimation or concern can of rarity environmental be made for these species at this time. In addition, the sand-silt habitats that Brachycercinae are found in are often not sampled adequately. Recent collections of C. youngi by WPM and AVP outside Nebraska would indicate that this species ismuch more common than Homoeoneuria is more previously thought. probably common than reports would indicate because its psammophilous habitat not taxonomic status has been adequately sampled. The of L. gravastella must be validated before estimates of rarity are assigned to it. Also, future studies of western species of the genus Paraleptophlebia should reveal the true commonness of P. a that not gregalis, species notably had been as far east as previously reported Nebraska. Historical and new faunistic data are reported below with no further comment. Presentation is alphabetical by family, genus, and species. All 8 GREAT PLAINS MAYFLIES

or not and whether or previous reports, whether published complete not, are Previous New state and records are given under reports. county in the first name of collectors are record given full. Only any given per in case If a (abbreviated the of present authors). species has previously for a additional records from that are not been reported county, county names in all letters for easier given here. County appear capital tracking. counties with stream are For reference, the location of along key systems on state in 1. Data are shown the Nebraska map given Fig. abbreviated as as to conserve The materials for which much possible printed space. new data are are in the Purdue Entomo record reported mostly deposited material logical Research Collection (West Lafayette, Indiana). However, associated with collectors names including Klubertanz (THK), Clopton, or Sorgenfrei are deposited in the private collection of THK (Janseville, new state are Wisconsin), except for material contributing records, which also deposited in PERC. Those with collectors name including Kondratieff (BCK), Harris, or Opler are deposited at the C. P. Gillette Museum of Diversity, Colorado State University (Fort Collins, Colorado).

FAUNISTIC DATA

BAETIDAE

Acentrella ampia Traver Previous Lunt as Baetis: no reports.?Carnevalo and (1982) county indicated (Niobrara R).

Acentrella insignificans (McDunnough) Previous reports.?Hamilton (1952) as Baetis bicaudatus: CHERRY (Niobrara R). Harris et al. (1999): SIOUX (Niobrara R). New county records.? BLAINE: N Loup R, Co Rd 1, VI-13-2000, THK; BROWN: Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; DAWES: Niobrara R, below Box Butte Dam, VI-15-1984, WPM; Niobrara R, VIII 10,VIII-25-1984; White R, Rt 385 bridge, VII-10-1984, HRL; HALL: Platte R, 2 mi N Doniphan, IX-28-1996, Sorgenfrei; KEITH: larvae, Otter Cr, St Hwy 92, V-22-1998, BCK; KEYA PAHA: Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; SHERIDAN: Niobrara R, Gordon, VII 11,VIII-21-1984, HRL.

Acentrella p?rvula (McDunnough) Previous reports.?Carnevalo (1981) as Pseudocloeon: CHERRY (Minnechaduza R, Snake R); SHERIDAN (Niobrara R). Decker (1981) as Pseudocloeon: DUNDY (Republican R); FRONTIER (Medicine Cr); FURNAS (Republican R); HAYES (Frenchman R); WEBSTER (Republican R). New county records.? BLAINE: Goose Cr, Co Rd 7, S Koshopah; N Loup R, Co Rd between Purdum & Brewster, VI-13-2000, THK; BROWN: Plum Cr, Hwy 20W Johnstown, VI-14-2000, BCK; DAWES: Niobrara R, below Box Butte Dam, VI-15-1984, WPM; White R, Crawford, VII-6-1984; White R, Ard Rd, VI-1-1984, HRL; KEITH: Otter Cr, St Hwy 92, V-22-1998, BCK; GARDEN: Blue Cr, vi-14-2000, BCK; LOUP: Calamus R, Hwy 183, W. P. MCCAFFERTY ET AL. 9

41 /56/49N 99/23/09W, VI-6-2000, WPM; PAWNEE: N Frk Big Nemaha R, St Rd 4,1 mi E Table Rock, VIII-12-1997, THK; RICHARDSON: Muddy Cr, Hwy 73,1 mi W Verd?n, IX-13-1996; S Frk Big Nemaha R, 8 mi SW Humboldt, V-22-1997, THK; SHERIDAN: Niobrara R, St Rd 27, VI-16 1984,WPM; Hay Springs Cr, V-29-1984, HRL; THOMAS: Dismal R, 13.9 mi S Thedford; Middle Loup R, entrance Neb Nat For, 1mi W Halsey, VI 12-2000, THK; WHEELER: Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI-6-2000, WPM.

Acentrella t?rbida (McDunnough) Previous reports.?Carnevalo (1981), Carnevalo and Lunt (1982) as Pseudocloeon Carolina (Banks): KEY A PAH A (Keya Paha R). Pine BCK. New county records.? BROWN: Long Cr, vi-13-2000,

Acerpenna pygmaea (Hagen) Previous reports.?Carnevalo (1981) as Baetis: CHERRY (Minnechaduza R); ROCK (Ash Cr). New county records.? BLAINE: N Loup R, Co Rd 1, VI-13-2000, THK; DAWES: Niobrara R, V-16-1979; HOLT: Elkhorn R, 1mi S Hwy 20,5 mi SE Stuart, VI-15-2000; S Frk Elkhorn R, Hwy 95, VI-26-1998, THK; LO GAN: S Loup R, Hwy 83,1.3 mi N Stapleton, VI-12-2000, THK; PAWNEE: N Frk Big Nemaha R, 1mi E Table Rock, Hwy 4, IX-3-1997, THK.

Apobaetis lakota McCafferty Previous report s.? McCafferty (2000b): SALINE (Big Blue R).

Baetis flavistriga McDunnough Previous reports.?Carnevalo (1981) as B. levitans: BOX BUTTE (Niobrara R). Carnevalo (1981) as B. quebecensis: CHERRY (Niobrara R); KEYA PAHA (Keya Paha R); KNOX (Niobrara R). Decker (1981) as B. levitans: HITCHCOCK (Republican R). Decker (1981) as B. quebecensis: FURNAS (Muddy Cr, Republican R); HAYES (RedWillow Cr).

Baetis intercalaris McDunnough Previous reports.?Decker (1981): FURNAS (Muddy Cr; Republican R); HAYES (RedWillow Cr). Klubertanz and Jones (1999): RICHARDSON (S Frk Big Nemaha R). New county records.? CASS: Platte R, Louisville L Prk, VII-16-1994, THK; DAWES: White R, Crawford, VII-6-1984; White R, N Chadron, VIII 13-1984, HRL; GAGE: Big Indian Cr, Hwy 77,1 mi SWymore, V-21-1997, THK; JOHNSON: nr Elk Cr, VIII-22-1997, THK; NEMAHA: Honey Cr, St Rd 67, 2 mi SE Peru, VI-18-1997; floodwaters Missouri R, Peru, VII-21 1997; Missouri R, Brownville, VIII-17-1994, THK; PAWNEE: N Frk Big Nemaha R, St Rd 4,1 mi E Table Rock, VIII-12-1997; Taylor Br, St Rds 4/ 65, Table Rock, V-21-1997, THK; SIOUX: Agate Cr, VIII-17-1984; Niobrara R, "Agate", VI-28-1984, HRL; Niobrara R, Agate Fossil Beds, VIII-11-1988, BCK;WASHINGTON: Brown Cr, Co Rd 26,41/30/33N 96/22/44W, VI 5-2000, WPM. 10 GREAT PLAINS MAYFLIES

Baetis magnus McCafferty and Waltz Previous reports.?McCafferty and Waltz (1986): DAWES (Chadron Cr, Rapid Cr, Squaw Cr, W Ash Cr); SIOUX (Sowbelly Canyon Cr). New county records.? CHERRY: trib. Niobrara R, Hwy 61, vi-14-2000, BCK.

Baetis tricaudatus Dodds Previous reports.?Decker (1981) as B. vagans: FRANKLIN (Cotton wood Cr); FURNAS (Republican R); HAYES (Frenchman R); HITCHCOCK (Republican R); Carnevalo (1981) as B. vagans: BOX BUTTE (Niobrara R); BROWN (Long Pine Cr); CHERRY (Niobrara R); HOLT (N Br Verdigris Cr); KNOX (Niobrara R); ROCK (Ash Cr). New county records.?CASS: Cr nr falls, Platte R Prk, VII-16-1994, THK; DAWES: Box Butte overflow pond; Chadron St Coll Pond; Niobrara R, below Box Butte Dam, VI-15-1984; Niobrara R, 2 mi E Marsland, VI-14 1984; Chadron Cr, Chadron St Prk, VI-10-1975, VI-16-1984, WPM; White R, Hwy 20, II-4-1995, BCK; Bordeaux Cr, V-25,VI-13-1984; W Ash Cr, VII 26,VIII-16-1984; Pepper Cr, VII-25,VIII-10-1984; Chadron Cr, V-9,VI 13,VII-18-1984; Niobrara R, V-27-1984; Niobrara R, below Box Butte Res at light, VIII-23-1984; White R, VI-l,7,ll,VII-2,6,20,VIII-15,17,IX-8-1984; Squaw Cr, VI-25,VII-26-1984, HRL; Squaw Cr, rd 707 SW Crawford, VII 8-1997, BCK; Dead Horse Cr, Hwy 20, III-l 1-1978;White Clay Cr; HALL: Platte R, St Rd 11/1-80, VI-26-1981, AVP; KEITH: Otter Cr, St Hwy 92, V 22-1998, BCK; KEYA PAHA: Niobrara R, Hwy 183, S Springview, VI-13 2000, THK; LOGAN: S Loup R, Rt 83, V-23-1989, HRL; NEMAHA: floodwaters Missouri R, Peru, VII-21-1997; Honey Cr, St Rd 67, 2 mi SE Peru, X-3-1996, THK; RICHARDSON: Muddy Cr, Hwy 73, 1 mi W Verd?n, V-25-1997, THK; SHERIDAN: Niobrara R, St Rd 27, VI-16-1984, WPM; Niobrara R, VIII-9-1984; Beaver Cr, VI-22,VII-30-1984, HRL; SIOUX: Niobrara R, Agate Springs Ranch, St Rd 29; Monroe Canyon Cr, Gilbert Baker StWildl Ref Campsite, VI-14-1984, WPM; Niobrara R, "Agate", VI at 28-1984; Soldier Cr, V-13,VI-ll,VII-6,20,VIII-15,IX-8-1984; Agate light, VII-23-1984; Spring Cr at light, VI-28-1984; Hat Cr, IV-2,V-14,VI-25-1979; HRL. Sowbelly Canyon Cr, VI-5,VII-23-1984,

Callibaetis ferrugineus (Walsh) Previous reports.?Hamilton (1952): SCOTTS BLUFF (Mitchell). New county records.? DAWES: Chadron Cr, VII-13-1984, VII-16-1984 (at light); Pepper Cr, VI-14,VII-19-1979, V-26,VI-27-1984; W Ash Cr, X-29 1977, HRL; GARFIELD: pond E Burwell, St Rd 91, 41/47/14N 99/07/ 13W, VI-6-2000, WPM; SIOUX: Sowbelly Canyon Cr, VIII-22-1984, HRL.

Callibaetis fluctuans (Walsh) Previous reports.? Hamilton (1952): LANCASTER (Lincoln); MADI SON (Norfolk); PIERCE (Plainview); PLATTE (Columbus); SCOTTS BLUFF (Mitchell, Scottsbluff). Hamilton (1952) as C. montanus: CASS (Plattsmouth Pond); SCOTTS BLUFF (Mitchell). New county records.? BROWN: marsh at Co Rd 7, EWillow L StWildl Mgmt Area, VI-13-2000, THK; BUFFALO: Kearney, IX-6-1969, Koss; W. P. MCCAFFERTY ET AL. 11

DAWES: Box Butte Res, overflow pond, VI-15-1984, WPM; Chadron St Coll at light, IX-20-1984; W Ash Cr, VII-10-1984; Chadron at light, VIII-14 1992, HRL; HALL: pond, Mormon IsRec Area, IV-26-1981, WPM; KEITH: Neven's Pond, VI-19-1996, Clopton; LOUP: Calamus R, Hwy 183,41 /56/ 49N 99/23/09W, VI-6-2000, WPM; MADISON: Norfolk, VIII-5-1949; NEMAHA: Peru St Coll at light, VIII-23-1996, THK; WHEELER: Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI-6-2000, WPM.

Callibaetis pallidus Banks Previous reports.?Hamilton (1952) as C. semicostatus: LANCASTER (Lincoln pond). New records.? KEITH: Neven's county Pond, VI-19-1996, Clopton; NEMAHA: Auburn at light, VI-12-1996; Peru St Coll at light, VIII-23 1996, THK.

Callibaetis pictus (Eaton) New state records.?-DAWES: larvae, Chadron Cr, VI-4-1984, HRL; KEITH: larvae, Neven's Pond, VI-19-1996, Clopton; NEMAHA: larvae, Honey Cr, St Rd 67, 2 mi S Peru, X-6-1996, THK.

Camelobaetidius variabilis Wiersema New state records.?KNOX: N Br larvae, Verdigre Cr, NW, SW, Sec. 33, T31N, R08W, VII-17-1996, D. Schumacher.

Camelobaetidius waltzi McCafferty Previous reports.?Klubertanz and Jones (1999): PAWNEE (N Frk Big Nemaha R); RICHARDSON (Muddy Cr, S Frk Big Nemaha R).

Camelobaetidius warreni (Traver and Edmunds) New state records.?BLAINE: larvae, N Loup R, Co Rd between Purdum & Brewster, VI-13-2000, THK; N Loup R, Co Rd 1,12 mi NW Brewster, VI 13-2000, BCK; BROWN: larvae, Niobrara R, Hwy 183, S Springview, VI 13-2000, THK; CHERRY: larvae, Niobrara R, Hwy 61, VI-14-2000, BCK; GARDEN: larvae, Blue Cr. vi-14-2000, BCK; KEYA PAHA: larvae, Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; LOUP: larvae, Calamus R, Hwy 183,41/56/49N 99/23/09W, VI-6-2000, WPM; SHERIDAN: larvae: Niobrara R, St Rd 27, VI-16-1984, WPM; Niobrara R, Peters, VII-18,27 1984; Niobrara R, Gordon, VII-11-1984, HRL; THOMAS: larvae, Mid Loup R, entrance Neb Nat For, 1mi W Halsey, VI-12-2000, THK.

Centroptilum album McDunnough Previous reports.?Hamilton (1952) as C. walshi: PLATTE (Columbus); SEWARD (Seward). Carnevalo (1981): KNOX (Niobrara R). Decker (1981): DUNDY (Republican R); HAYES (Frenchman R); HITCHCOCK (French man R, Republican R). New county records.? RICHARDSON: S Frk Big Nemaha R, Hwy 8,8 mi SW Humboldt, at light, VII-23-1997, THK. 12 GREAT PLAINS MAYFLIES

Centroptilum bifurcatum McDunnough New state records: BROWN: larvae, Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; Plum Cr, Hwy 20 W Johnstown, VI-14 2000, BCK; CHERRY: larvae & adults, Snake R, Rt 61, VI-6-1995; larvae, Niobrara R, Hwy 61, VI-14-2000, BCK; GARDEN: larvae, Blue Cr, Rackett Rd, V-22-1990, BCK; HALL: larvae, Platte R, St Rd 11/1-80, IV-26-1981, WPM; KEYA PAHA: larvae, Niobrara R, Hwy 183, S Springview, VI-13 2000, THK; LOUP: larvae, Calamus R, Hwy 183,41/56/49N 99/23/09W, VI-6-2000, WPM; SIOUX: larvae, Niobrara R, Agate Springs Ranch, St Rd 29, VI-14-1984, WPM; THOMAS: larvae, Dismal R, 13.9mi S Thedford, VI 12-2000, THK; WHEELER: larvae, Cedar R, St Rd 70/91E Ericson, 41 /47/ 00N 98/41/53W, VI-6-2000, WPM.

convexum Centroptilum Ide Previous reports.?Carnevalo (1981): BROWN (Niobrara R); CHERRY (Minnechaduza R, Niobrara R); KNOX (Niobrara R). Decker (1981): DUNDY (Republican R, S Frk Republican R); HAYES (Frenchman R); HITCHCOCK (Republican R); SHERIDAN (Niobrara R).

Diphetor hageni (Eaton) Previous reports.?Carnevalo (1981), Carnevalo and Lunt (1982) as Baetis: CHERRY (Minnechaduza R); KNOX (N Br Verdigris Cr).

Fallceon quilleri (Dodds) Previous reports.?Klubertanz and Jones (1999): PAWNEE (N Frk Big Nemaha R); PLATTE (Columbus); RICHARDSON (S Frk Big Nemaha R). Harris et al. (1999): SIOUX (Niobrara R). New county records.? BLAINE: Dismal R, St Rd 2, S Dunning; N Loup R, Co Rd between Purdum & Brewster, VI-13-2000, THK; N Loup R, Co Rd 1,12 mi NW Brewster, VI-13-2000, BCK; BROWN: Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; CASS: Platte R, Louisville L Prk, VII 16-1994, THK; CHERRY: Niobrara R, Hwy 61; Leander Cr, Hwy 61VI-14 2000, BCK; DAWES: Niobrara R, below Box Butte Dam, VI-15-1984, WPM; Pepper Cr, V-26,VII-12-1984; Dead Horse Cr; E Ash Cr, VII-24 1984; Chadron Cr, IV-4,25,V-31,VII-19,VIII-14-1984; Bordeaux Cr, VII 30,VIII-13-1984, HRL; Squaw Cr, Rd 707 SW Crawford, VII-8-1997, BCK; DODGE: Elkhorn R, St Rd 91,41/32/21N 96/27/15W, VI-5-2000, WPM; FURNAS: Republican R at Oxford, VIII-11-1982, AVP; GAGE: Plum Cr, 0.8 mi S St Rd 8 toOketo, V-30-1997; Turkey Cr, 4mi N Holmesville, VII 16-1994, THK; HOLT: Elkhorn R, 1mi S Hwy 20, 5 mi SE Stuart, VI-15 2000, THK; JOHNSON: nr Elk Cr, VIII-22-1997, THK; KEYA PAHA: Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; LOGAN: S Loup R, Hwy 83,1.3 mi S Thedford, VI-12-2000, BCK; NEMAHA: Floodwaters Missouri R, Peru, VII-20-1997; Honey Cr, St Rd 67,2 mi S Peru, X-3-1996; Missouri R, Brownville, VIII-17-1994, THK; SARPY: Platte R, St Rd 31,1 mi E Schramm Prk, VII-6-1996, THK; SHERIDAN: Beaver Cr, VI 8,21,25,VII-3,18,VIII-9-1984; Niobrara R, VIII-21-1984, HRL; SIOUX: Sol dier Cr, VII-15-1979, VIII-15-1984; White R, VII-19-1979, IX-8-1984, HRL; Niobrara R, Agate Fossil Beds, VIII-25-1988, BCK; THOMAS: Mid Loup W. P. MCCAFFERTY ET AL. 13

R, Entrance Neb Nat For, 1mi W Halsey, VI-12-2000, THK; WHEELER: Cedar R, St Rd 70/91 E Ericson, VI-6-2000, WPM.

Paracloeodes minutus (Daggy) Previous reports.?Carnevalo (1981): CHERRY (Niobrara R); SHERIDAN (Niobrara R). Decker (1981): DUNDY (Republican R, S Frk Republican R); FRANKLIN (Turkey Cr); FURNAS (Republican R); HITCHCOCK (Republican R); RED WILLOW (Republican R). New county records.? BLAINE: N Loup R, Co Rd 1, VI-13-2000, THK; BROWN: Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; BUF FALO: Platte R, Kearney, VIII-12-1982, AVP; GARDEN: Blue Cr, vi-14 2000, BCK; JOHNSON: nr Elk Cr, VIII-22-1997, THK; KEYA PAHA: Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; NEMAHA: Honey Cr, St Rd 67,2 mi S Peru, X-6-1996, THK; PAWNEE: N Frk Big Nemaha R, 4 mi N Table Rock, VIII-15-1997; N Frk Big Nemaha R, 1mi E Table Rock, Hwy 4, IX-3-1997, THK; RICHARDSON: Muddy Cr, Hwy 73,1 mi W Verd?n, V-25-1997, THK.

Plauditus dubius (Walsh) Previous reports.?Hamilton (1952) as Pseudocloeon: SEWARD (Seward). Carnevalo (1981) as Pseudocloeon: BOX BUTTE (Niobrara R); BROWN (Long Pine Cr); CHERRY (Minnechaduza R); HOLT (N Br Verdigris Cr); KNOX (Niobrara R); SHERIDAN (Niobrara R).

Plauditus punctiventris (McDunnough) as or Previous reports.?Carnevalo (1981) Pseudocloeon P. myrsum: BROWN (Long Pine Cr); CHERRY (Minnechaduza R); HOLT (N Br Verdigris Cr); KEYA PAHA (Keya Paha R); KNOX (Niobrara R, N Br Verdigris Cr); SHERIDAN (Niobrara R). New county records.? DAWES: Niobrara R, below Box Butte Dam, VI 15-1984, WPM; GARDEN: Blue Cr, vi-14-2000, BCK; LOGAN: S Loup R, Hwy 83,1.3 mi N Stapleton, VI-12-2000, BCK; LOUP: Calamus R, Hwy 183, 41/56/49N 99/23/09W, VI-6-2000, WPM; RICHARDSON: Muddy Cr, Hwy 73,1 mi W Verd?n, V-25-1997; S Frk Big Nemaha R, St Rd 8,8 mi SW Humboldt, V-21-1997, THK; SIOUX: Niobrara R, Agate Springs Ranch, St Rd 29, VI-14-1984, WPM; WHEELER: Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI-6-2000, WPM.

Procloeon rufostrigatum (McDunnough) New state records: DODGE: larvae, Elkhorn R, St Rd 91,41/32/21N 96/27/15W, VI-5-2000, WPM; RICHARDSON: larvae, S Frk Big Nemaha R, St Rd 8, 8mi SW Humboldt, VIII-3-1997, THK.

Pseudocloeon dardanum (McDunnough) Previous reports.?-Harris et al. (1999): SIOUX (Niobrara R). New county records.? BLAINE: Dismal R, St Rd 2, S Dunning, VI-13-2000, THK; Dismal R, Co Rd off Hwy 83,13.9 mi S Thedford, VI-12-2000, BCK; CASS: Platte R, Louisville L Prk, VII-16-1994, THK; DODGE: Elkhorn R, StRd 91,41 /32/21N 96/27/ 15W, VI-5-2000, WPM; DOUGLAS: Missouri 14 GREAT PLAINS MAYFLIES

R, Dodge Prk, Omaha, VI-10-1997, THK; GAGE: Big Blue R, bridge E Hoag, VI-20-1989, THK; GREELEY: Cedar R, St Rd 91,41 /41 /50N 98/25/ 23W, VI-6-2000, WPM; LOUP: Calamus R, Hwy 183,41/56/49N 99/23/ 09W, VI-6-2000, WPM; NEMAHA: Missouri R, Peru, VI-11-1996, THK; RICHARDSON: S Frk Big Nemaha R, St Rd 8,8 mi SW Humboldt, V-21 1997, THK; SARPY: Platte R, St Rd 31,1 mi E Schramm Prk, VII-6-1996, THK; THOMAS: Dismal R, 13.9 mi S Thedford, VI-12-2000, THK; VAL LEY:Middle Loup R, Arcadia, VI-25-1998, BCK;WHEELER: Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI-6-2000, WPM.

Pseudocloeon frondale (McDunnough) Previous reports.?Hamilton (1952) as Baetis australis: HOLT (Cache Cr).

Pseudocloeon longipalpus (Morihara and McCafferty) New state records: CASS: larvae, Platte R, Louisville L Prk, VII-16 1994, THK; NEMAHA: larvae:Missouri R, Brownville, VII-23-1996; flood waters Missouri R, Peru, VII-23-1996, THK; RICHARDSON: larvae, S Frk Big Nemaha R, St Rd 8, 8mi SW Humboldt, V-21-1997, THK.

Pseudocloeon propinquum (Walsh) New state records: BLAINE: larvae: Goose Cr, St Rd 7, S Koshopah; N Loup R, Co Rd 1, VI-13-2000, THK; BROWN: larvae, Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; Plum Cr, Hwy 20W Johnston, VI-14 2000, BCK; BUFFALO: adults, Kearney, IX-6-1969, Koss; CHERRY: lar vae, Snake R, S Hwy 61, VI-5-1995; Dry Cr, Merriman; Niobrara R, Hwy 61; Leander Cr, Hwy 61, VI-14-2000, BCK; DAWES: adults: Niobrara R, below Box Butte Dam, VI-15-1984; Niobrara R, 2 mi E Marsland, VI-14 1984; larvae: Chadron Cr, .5mi S Chadron St Prk, VI-12-1984, WPM; FURNAS: adults, Republican R, Oxford R channel, VIII-11-1982 AVP; GARDEN: Blue Cr, vi-14-2000, BCK; HOLT: larvae, Elkhorn R, 1mi S of Hwy 20,5 mi SE Stuart, VI-15-2000, THK; KEYA PAHA: larvae, Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; LOGAN: larvae, S Loup R, Hwy 83,1.3 mi N Stapleton, VI-12-2000, THK; LOUP: larvae, Calamus R, Hwy 183,41 /56/49N 99/23/09W, VI-6-2000, WPM; SHERIDAN: larvae: Niobrara R, St Rd 27, VI-16-1984, WPM; Niobrara R, V-29,VIII-9-1984; Pine Cr, Hwy 250, HRL; SIOUX: adults, Niobrara R, Agate Springs Ranch, St Rd 29, VI-14-1984, WPM; larvae, Niobrara R, VI-14-1984, HRL; THO MAS: larvae, Dismal R, 13.9 mi S Thedford; Mid Loup R, entrance Neb Nat For, 1mi W Halsey, VI-12-2000, THK; WHEELER: larvae, Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI-6-2000, WPM.

BAETISCIDAE

Baetisca lacustris McDunnough as Previous reports.?Carnevalo (1981) B. bajkovi: KEYA PAHA (Keya Paha R). W. P. MCCAFFERTY ET AL. 15

CAENIDAE

Amercaenis ridens (McDunnough) Previous reports.?Hamilton (1952) as Caenis: DAWSON (Cozad). Decker (1981) as Caenis: HITCHCOCK (Republican R). Provonsha and McCafferty (1985): CHERRY (Niobrara R); FURNAS (Republican R); WEBSTER (Republican R); RED WILLOW (Republican R). New county records.? BUFFALO: Kearney at light, VIII-10-1982, AVP; CASS: Platte R, Louisville L Prk, VII-16-1994, THK; NEMAHA: Auburn at light, VII-22-1996; Floodwaters Missouri R, Peru, VII-21-1997, THK; PLATTE: Platte R, S Duncan, VIII-8-1993, BCK; SARPY: Platte R, St Rd 31, 1mi E Schramm Prk, VII-6-1996, THK.

Brachycercus edmundsi Sold?n New state records: BLAINE: larvae, Goose Cr, Co Rd 7 Koshopah, VI 13-2000, THK; HALL: larvae, Platte R, St Rd 11/1-80, IV-26-1981; WPM; SHERIDAN: larvae: Niobrara R, St Rd 27, VI-16-1984, WPM; Niobrara R, Gordon, VIII-11-1984; Niobrara R, V-29,VI-8,VIII-27-1984, HRL; WHEELER: larvae, Cedar R, St Rd 70/90 E Ericson, 41/47/00N, 98/41/ 53W, VI-6-2000, WPM.

Brachycercus nasutus Sold?n New state records: SHERIDAN: larvae: Niobrara R, S Gordon, VII-27 1984; Niobrara R, Gordon, VII-11-1984, HRL.

Brachycercus prudens (McDunnough) Previous reports.?Hamilton (1952): PLATTE (Columbus). New HAYES: E county records.? Frenchman R, Hwy 6,4.7 mi Waunita, VI-12-1994, BCK.

Caenis arnica Hagen Previous reports.?Hamilton (1952): DAKOTA (South Sioux City). Hamilton (1952) as C. simulans: BOX BUTTE (Alliance); GRANT (Hyannis); PIERCE (Pierce); SIOUX (Univ L). Provonsha (1990): CASS (Weeping Water Cr Impoundment); CHERRY (Sparks); DAWES (Niobrara R); DOUGLAS (Papio Cr); HOLT (Papio Cr); PAWNEE (Johnson Cr). New county records.? BROWN: Keller Prk St Rec Area at light, Hwy 183, 9.6 mi NE Ainsworth, VI-14-2000, THK; FURNAS: Oxford at light, VIII-11-1982, AVP; GARFIELD: pond E Burwell, St Rd 91,41 /47/14N 99/ 07/13W, VI-6-2000, WPM; HAYES: Frenchman R, Hwy 6, 4.7 mi E Waunita, VI-12-1994, BCK.

Caenis bajaensis Allen and Murvosh Previous reports.?Provonsha (1990): DAWES (Bordeaux Cr, Chadron Cr, Chadron St Coll Pond, Sowbelly Cr); SHERIDAN (Beaver Cr); SIOUX (White R).

Caenis hilaris (Say) Previous reports.?Hamilton (1952): PLATTE (Columbus); RED WIL 16 GREATPLAINS MAYFLIES

LOW (McCook). Provonsha (1990): CHERRY; FURNAS (Republican R). New county records.? BLAINE: Goose Cr, St Rd 7, S Koshopah; N Loup R, Co Rd between Purdum & Brewster, VI-13-2000, THK; N Loup R, Co Rd 1,12 mi NW Brewster, VI-13-2000, BCK; BROWN: Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; DAWES: White R, VIII-15-1984, HRL; KEYA PAHA: Niobrara R, Hwy 183, S Springview, VI-13-2000, THK; NEMAHA: floodwaters Missouri R, Peru, VII-21-1997; Peru St Coll at light, Peru, VII-17-1995, THK; PAWNEE: N Frk Big Nemaha R, 4 mi N Table Rock, VIII-15-1997, THK; RICHARDSON: S Frk Big Nemaha R, St Rd 8,8 mi SW Humboldt, VII-31-1997, THK; SARPY: Platte R, St Rd 31,1 mi E Schramm Pk, VII-6-1996, THK; SHERIDAN: Niobrara R, S Gordon, VII-27-1984; Niobrara R, VIII-21-1984, HRL; THOMAS: Dismal R, 13.9mi S Thedford; Mid Loup R, Entrance Neb Nat For, 1mi W Halsey, VI-12 2000, THK.

Caenis latipennis Banks Previous reports.?Hamilton (1952) as C. forcipata: RED WILLOW (McCook). Provonsha (1990): BOX BUTTE (Niobrara R); CHASE (Cham pion L); CHERRY (Sparks); DAWES (Chadron St Coll Pond); FURNAS (Republican R); HITCHCOCK (Frenchman R); HOLT; LINCOLN (Jeffrey Res); SHERMAN (Mid Loup R). New county records.? BROWN: Plum Cr, Hwy 20W Johnstown, VI-14 2000, BCK; BUFFALO: Kearney at light, VIII-10-1982, AVP; DUNDY: Republican R, Hwy 61 S Beukleman, V-20-1980, Decker; FRANKLIN: Thompson Cr, Riverton, VII-30-1980, Decker; GAGE: Turkey Cr, 4 mi N Holmesville, VII-16-1994, THK; GARDEN: Blue Cr, Rocket Rd, V-22 1998, BCK; HALL: pond, Mormon Is Rec Area, IV-26-1981; Platte R, St Rd 11/1-80, IV-26-1981, WPM; JOHNSON: nr Elk Cr, VIII-22-1997, THK; LANCASTER: Branched Oak L at Prk, VII-16-1994, THK; LOGAN: S Loup R, Hwy 83, 1.3 mi N Stapleton, VI-12-2000, BCK; NEMAHA: floodwaters Missouri R, Peru, VII-21-1997, THK; SAUNDERS: Rock Cr, Ceresco, IV-20-1980, Kaiisch; SCOTTS BLUFF: N Platte R, overflow pond, NE 71, IX-16-1989, Harris; SHERIDAN: Niobrara R, VIII-9-1977, Gibson; Niobrara R, Gordon, VIII-11-1984, HRL; SIOUX: Niobrara R, Agate Springs Ranch, St Rd 29, VI-14-1984, WPM; Agate Fossil Beds, Niobrara R, VII-11-1989, BCK; WASHINGTON: Brown Cr, Co Rd 26, 41/30/33N 96/22/44W, VI-5-2000, WPM.

Caenis tardata McDunnough Previous reports.?Provonsha (1990): DUNDY (S Frk Republican R); FURNAS (Republican R); HOLT; HITCHCOCK (Republican R);MERRICK (Platte R); SHERIDAN (Niobrara R); SHERMAN (Mid Loup R);WEBSTER (Republican R). New county records.? DAWES: Niobrara R, below Box Butte Dam, VIII-23-1984, HRL; DODGE: Elkhorn R, St Rd 91,41 /32/21N 96/27/ 15W, VI-5-2000, WPM; LOUP: Calamus R, Hwy 183,41/54/49N 99/23/09W, VI-6-2000, WPM; SIOUX: Agate Springs at light, VII-23-1984, HRL; WHEELER: Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI 6-2000, WPM. W. P. MCCAFFERTY ET AL. 17

Caenis youngi Roemhild New state records: BROWN: adult, Keller Prk St Rec Area, Hwy 183, 9.6 mi NE of Ainsworth, at light, VI-14-2000, THK.

Cercobrachys serpentis Sold?n New state records: FURNAS: larvae & adults, Republican R, Oxford R channel, VIII-11-1982, AVP; PAWNEE: larvae, N Frk Big Nemaha R, 1 mi E Table Rock, St Rd 4, VIII-12-1997, THK; SHERIDAN: larvae: Niobrara R, Gordon, VII-11,VIII-21-1984; Niobrara R, S Gordon, VII-27-1984, HRL.

EPHEMERELLIDAE

Ephemerella aurivillii (Bengtsson) Previous reports.?-Decker (1981): FRONTIER (Medicine Cr); HAYES (Frenchman R); HITCHCOCK (Frenchman R, Republican R).

Ephemerella inermis Eaton Previous reports.?Carnevalo (1981), Carnevalo and Lunt (1982) as E. inermis, E. infrequens, or E. lacustris: BROWN (Long Pine Cr); CHERRY (Minnechaduza R, Niobrara R); KEYA PAHA (Keya Paha R); ROCK (Ash Cr). Decker (1981), Decker and Lunt (1982) as E. inermis or E. dorothea: FRONTIER (Medicine Cr); HAYES (Frenchman R); HITCHCOCK (French man R, Republican R). New county records.? BLAINE: Goose Cr, St Rd 7, S of Koshopah, VI 13-2000, THK; DAWES: Niobrara R, below Box Butte Dam, VI-15-1984, WPM; Niobrara R, Marsland, VI-1-1984, HRL; LOUP: Calamus R, Hwy 183,41/56/49N 99/23/09W, VI-6-2000, WPM; SHERIDAN: Niobrara R, Rt 87, IV-30-1979, VI-11-1979; V-29-1984, HRL; SIOUX: Niobrara R, Agate Springs Ranch, St Rd 29, VI-14-1984, WPM; THOMAS: Dismal R, 13.9 mi S of Thedford, VI-12-2000, THK; Mid Loup R, Thedford, V-23-1989, HRL; WHEELER: Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI 6-2000, WPM.

EPHEMERIDAE

Hexagenia bilineata (Say) Previous reports.?Hamilton (1952): MADISON (Norfolk). Swanson (1967): KNOX (Lewis and Clark L [Missouri R]). New county records.? DAWES: Chadron at light, VIII-2-1991, HRL.

Hexagenia limbata (Serville) Previous reports.?Spieth (1941): LANCASTER (Lincoln). Hamilton (1952, 1959): BUFFALO (Kearney); BROWN (Plum Cr); CHERRY (Minnechaduza R); DAWSON (Johnson L, Lexington, Willow Is);HALL (Wood R); KEITH (Ogallala); KNOX (Bazille Cr); LINCOLN (N Platte); MADISON (Norfolk); PLATTE (Columbus); SARPY (Linoma Beach ditch); SCOTTS BLUFF (Mitchell, Scottsbluff); SEWARD (Milford, Seward); THOMAS (Halsey). Pesek (1974): LANCASTER (Salt Cr). Moul (1984): LANCASTER (Bluestem L). Harris et al. (1999): GAGE (Cub Cr); SIOUX (Niobrara R). 18 GREAT PLAINS MAYFLIES

New county records.? BLAINE: N Loup R, Co Rd 1, 12 mi NW Brewster; Dismal R, St Rd 2mi S Dunning, VI-13-2000, BCK; BOX BUTTE: Niobrara R, XI-12-1978, Muenchau; DAWES: Niobrara R, Marsland, VI 1-1984, HRL; FURNAS: Oxford river channel & Oxford at light, VIII-11 1982, AVP; GAGE: Homestead, 2.5 mi NW Beatrice, VI-20-1989, BCK; KEYA PAHA: Niobrara R, Hwy 183 S Springview, VI-13-2000, BCK; LOGAN: S Loup R, Hwy 83, 1.3 mi N Stapleton, VI-12-2000, THK; NEMAHA: Auburn at light, VII-12-1995; Peru at light, VII-15-1997, THK; RED WILLOW: Republican R, 1mi S Perry; SHERIDAN: Niobrara R, St Rd 27, V-16-1984, WPM; Niobrara R, Gordon, VIM 1-1984, HRL; WHEELER: Cedar R, St Rd 70/91, E Ericson, 41 /47/00N 98/41 /53W, VI 6-2000, WPM.

Pentagenia vittigera (Walsh) Previous reports.?Hamilton (1952, 1959): MADISON (Norfolk); PLATTE (Columbus). Swanson (1967): KNOX (Lewis and Clark L [Mis souri R]). THK. New county records.? NEMAHA: Missouri R, Peru, VII-21-1997,

HEPTAGENIIDAE

Heptagenia diabasia Burks Previous reports.?Hamilton (1952): BLAINE (Dismal R); HOLT (Ewing); KNOX (Bazille Cr); LOUP (Calamus R); MADISON (Norfolk); NEMAHA (Plum Cr); PIERCE (Pierce); PLATTE (Columbus); RICHARDSON (Falls City str); SCOTTS BLUFF (Scottsbluff irrigation canal). Carnevalo (1981): BOX BUTTE (Niobrara R); BROWN (Niobrara R); CHERRY (Minnechaduza R, Niobrara R); HOLT (N Br Verdigris Cr); KEYA PAHA (Keya Paha R); KNOX (Niobrara R); ROCK (Ash Cr); SEWARD (Seward); SHERIDAN (Niobrara R); SIOUX (Univ L); THAYER (Alexandria); THOMAS (Loup R); WASHINGTON (Herman str); WHEELER (Cedar R). Decker (1981):DUNDY (Republican R); FRANKLIN (Cottonwood Cr, Thompson Cr, Turkey Cr); FRONTIER (Medicine Cr); FURNAS (Muddy Cr, Republican R); HAYES (Frenchman R, Red Willow Cr); HITCHCOCK (Frenchman R, Republican R); RED WILLOW (Repub lican R);WEBSTER (Republican R). Angle (1987): SCOTTS BLUFF (Nine Mile Cr). Darrow and Preuss (1989): Lancaster (Haines Br). Harris et al. (1999): SIOUX (Niobrara R). New county records.? CASS: Platte R, Louisville L Prk, VII-16-1994, THK; DAWES: White R, Whitney, VII-20-1984; White R, Crawford, VII 20-1984; Niobrara R, Marsland, VI-1-1984; Bordeaux Cr, VII-30-1984; Chadron Cr, VII-23-1984, HRL; DODGE: Fremont at light; Elkhorn R, St Rd 91,41 /32/21N 96/27/ 15W, VI-5-2000, WPM; DOUGLAS: Missouri R, Dodge Prk, Omaha, VI-10-1997, THK; GAGE: Big Indian Cr, Hwy 77,1 mi SWymore, V-21-1997, THK; HALL: Platte R, St Rds 11/180, IV-26-1981, WPM; JOHNSON: nr Elk Cr, VIII-22-1997, THK; KEITH: Ogallala at light, VI-22-1981, AVP; LINCOLN: N Platte at light, VII-6-1981, AVP; LOGAN: S Loup R, Hwy 83,1.3 mi N Stapleton, VI-12-2000, THK; PAWNEE: N Frk Big Nemaha R, St Rd 4,1 mi E Table Rock, VII-31-1997; Taylor Br, St Rds W. P. MCCAFFERTY ET AL. 19

4/65, Table Rock, V-21-1997, THK; VALLEY: N Loup R, Ord, park, VI-25 1998, BCK.

Heptagenia elegantula (Eaton) Previous reports.?Traver (1935): LANCASTER (Lincoln). Hamilton (1952): MADISON (Norfolk); SEWARD (Seward). Keller Prk St Rec New county records.? BROWN: Bone Cr, Area, Hwy 183,9.6 mi NE Ainsworth; Long Pine Cr, Long Pine StWildl Mgmt Area, 0.5mi N Long Pine, VI-13-2000, THK; DAWES: White R 8mi NE Chadron, Bordeaux gravel rd, VI-17-1984, WPM; Cr, III-30,V-18-1978,111-21-1979, VII-16-1984; White R, Ft Rob, VI-1-1984; White R, Peters, VII-18-1984; White R, 111-21-1979, VI-7-1984; White R, Whitney, VII-20-1984; White R, Ard Rd, VI-1-1984; White R, Crawford, VI-ll,VII-6,20-1984; White R, N Chadron, V-25-1984, HRL; NEMAHA: floodwaters Missouri R, Peru, VI 11-1996, THK; RICHARDSON: S Frk Big Nemaha R, St Rd 8, 8 mi SW Humboldt, V-22-1997, THK; SARPY: Platte R, St Rd 31,1 mi E Schramm Prk, VII-6-1996, THK; SHERIDAN: Niobrara R, St Rd 27, VI-16-1984, WPM; Niobrara R, VI-11-1979; Niobrara R, Peters, VIII-27-1984; Niobrara R, Gordon, VII-11-1984, HRL; SIOUX: Agate at light, VII-23-1984, HRL; THOMAS: Mid Loup R, entrance Neb Nat For, 1mi W Halsey, VI-12-2000, THK.

Heptagenia flavescens (Walsh) Previous reports.?Carnevalo (1981): BROWN (Niobrara R); KEYA PAHA (Keya Paha R); KNOX (Niobrara R). Decker (1981): DUNDY (Republican R); FRANKLIN (Cottonwood Cr, Thompson Cr); FURNAS (Muddy Cr, Republican R); HITCHCOCK (Frenchman R); RED WILLOW (Republican R); WEBSTER (Republican R). L New county records.? CASS: Platte R, Louisville Prk, VII-16-1994, THK; DODGE: Fremont at light, VI-5-2000, WPM; GAGE: Big Blue R, Chataqua City Prk, Beatrice, V-21-1997, THK; NEMAHA: Auburn at Missouri Missouri light, VII-17-1995; floodwaters R, Peru, VII-20-1997; R, Brownville, VIII-17-1994; Peru St Coll at light, Peru, VI-5,22-1995, THK; RICHARDSON: S Frk Big Nemaha R, St Rd 8,8 mi SW Humboldt, VII-21 1997, THK.

Leucrocuta hebe (McDunnough) Previous reports.?Decker (1981) asHeptagenia: HITCHCOCK (French man R).

Leucrocuta maculipennis (Walsh) Previous reports.?Carnevalo (1981) asHeptagenia: KEYA PAHA (Keya Paha R). New county records.? DAWES: Chadron at light, VII-1-1996, HRL; NEMAHA: Auburn at light, VIII-5-1995; Peru St Coll at light, Peru, VIII 4-1997, THK; RICHARDSON: S Frk Big Nemaha R, St Rd 8, 8 mi SW Humboldt, VII-21-1997, THK. 20 GREAT PLAINS MAYFLIES

Macdunnoa persimplex (McDunnough) Previous reports.?Traver (1935) as Heptagenia: LANCASTER (Lin coln). Hamilton (1952) as Heptagenia: MADISON (Norfolk); PIERCE (Pierce); SEWARD (Seward). New county records.? NEMAHA: Peru St Coll at light, IV-22,23 1995,VI-21,29-1998; Peru Boat Dock, VI-4-1996, THK.

Raptoheptagenia cruentata (Walsh) Previous reports.?Traver (1935) as Heptagenia: LANCASTER (Lin coln). New records.? Missouri VI county DOUGLAS: R, Dodge Prk, Omaha, 10-1997, THK; NEMAHA: Auburn at light, VI-27-1997; Peru St Coll at light, VI-22-1995, THK.

Stenacron interpunctatum (Say) Previous reports.?Hamilton (1952) as Stenonema: DAWSON (Cozad); DODGE (Crowell); MADISON (Norfolk). Decker (1981): FRONTIER (Medicine Cr); FURNAS (Muddy Cr); HAYES (Frenchman R, Red Willow Cr); RED WILLOW (Republican R); WEBSTER (Republican R). Harris et al. (1999): GAGE (Cub Cr). New county records.? BUFFALO: S Loup R, Hwy 183,Milton Store, VI 20-1989, BCK; DAWES: Bordeaux Cr, 7 mi N Chadron, V-24,25-1984; White R, VI-7-1984; Chadron at light, VII-1-1996, VIII-1,7-1998, HRL; LANCASTER: Branched Oak L at Prk, VII-16-1994, THK; NEMAHA: Auburn at light, VIII-5-1996; Honey Cr, St Rd 67,2 mi SE Peru, VI-11-1997; Peru St Coll at light, Peru, VI-20-1995, THK; PAWNEE: Taylor Br, St Rds 4/65, Table Rock, V-21-1997, THK; RICHARDSON: Long Br, 1.1mi E St Rd 105, V-21-1997; Muddy Cr, Hwy 73,1 mi W Verd?n, IV-25-1997; S Frk Big Nemaha R at light, St Rd 8, 8 mi SW Humboldt, VII-23-1997, THK.

Stenacron minnetonka (Daggy) Previous reports.?Decker (1981): FRONTIER (Medicine Cr); HAYES (RedWillow Cr).

Stenonema exiguum Traver New state records: GAGE: larvae, Big Blue R, Chataqua City Prk, Beatrice, V-21-1997, THK; RICHARDSON: larvae, S Frk Big Nemaha R, St Rd 8,8 mi SW Humboldt, VII-31-1997, THK; WHEELER: larvae, Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI-6-2000, WPM.

Stenonema femoratum (Say) New state records: PAWNEE: larvae, Taylor Br, St Rds 4/65, Table Rock, VII-31-1997, THK; RICHARDSON: larvae, Hwy 73,1 mi W Verd?n, III-20-1997, THK.

Stenonema mexicanum (McDunnough) Previous reports.?Hamilton (1952) as S. bellum: CUMING (West Point). Carnevalo (1981), Carnevalo and Lunt (1982) as S. integrum: KNOX (Niobrara R). Decker (1981), Decker and Lunt (1982) as S. integrum: W. P. MCCAFFERTY ET AL. 21

FURNAS (Muddy Cr); RED WILLOW (Republican R); WEBSTER (Re publican R). Darrow and Pruess (1989) as S. integrum: LANCASTER (Haines Br). New county records.? CASS: Platte R, Louisville L Prk, VII-16-1994, THK; DODGE: Fremont at light, VI-5-2000, WPM; DOUGLAS: Missouri R, Dodge Prk, Omaha, VI-10-1997, THK; GAGE: Big Blue R, bridge E Hoag, VI-20-1989, BCK; Big Blue R, Chataqua City Pk, Beatrice, V-21 1997, THK; NEMAHA: Floodwaters Missouri R, Peru, VII-21-1997; Mis souri R, Brownville, VIII-17-1994; Peru St Coll at light, Peru, VI-5-1995, THK; PAWNEE: N Frk Big Nemaha R, St Rd 4,1 mi E Table Rock, VII 31,VIII-12-1997, THK; RICHARDSON: S Frk Big Nemaha R at light, St Rd 8,8 mi SW Humboldt, VII-23,VIII-25-1997, THK; SARPY: Platte R, St Rd 31,1 mi E Schramm Prk, VII-6-1996, THK.

Stenonema modestum (Banks) Previous reports.?Decker (1981) as S. rubrum:WEBSTER (Republican R).

Stenonema pulchellum (Walsh) Previous reports.?"Decker (1981):WEBSTER (Republican R). New county records.? LOUP: Calamus R, Hwy 183, 41/56/49N 99/ 23/09W, VI-6-2000, WPM.

Stenonema terminatum (Walsh) Previous reports.?Hamilton (1952) as S. luteum: LANCASTER (Lin coln). Bednarik and McCafferty (1979): ANTELOPE (Neligh). Carnevalo (1981) as S. ares: KNOX (Niobrara R). Decker (1981) as S. ares: FURNAS (Republican R); FRONTIER (Medicine Cr); HITCHCOCK (Frenchman R). Klubertanz and Jones (1999): PAWNEE (N Frk Big Nemaha R); RICHARDSON (S Frk Big Nemaha R). New county records.? CASS: Platte R, Louisville L Prk, VII-16-1994, THK; DAWES: White R, 8 mi NE Chadron, VI-17-1984, WPM; White R, Slim Buttes, VII-17-1984, HRL; DODGE: Fremont at light, VI-5-2000, WPM; GAGE: Big Blue R, Chataqua City Prk, Beatrice, V-21-1997; Big Indian Cr, Hwy 77,1 mi SWymore, V-21-1997; Plum Cr, 0.8 mi S St Rd 8 to Oketo, V-30-1997, THK; LOUP: Calamus R, Hwy 183,41/56/49N 99/ 23/09W, VI-6-2000, WPM; SHERIDAN: Niobrara R, St Rd 27, VI-16-1984, WPM; SIOUX: Spring Cr, V-1984, HRL; WHEELER: Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI-6-2000, WPM.

Stenonema vicarium (Walker) Previous reports.?-Harris et al. (1999): GAGE (Cub Cr). New records.? DODGE: Fremont at county adults, light, VI-5-2000, WPM.

ISONYCHIIDAE

Isonychia bicolor (Walker) New state records: DODGE: adults, Fremont at light, VI-5-2000, WPM. 22 GREATPLAINS MAYFLIES

Isonychia rufa McDunnough Previous report s.? Hamilton (1952): MADISON (Norfolk); SEWARD (Seward). Kondratieff and Voshell (1984): LANCASTER (Lincoln); LIN COLN (North Platte). Harris et al. (1999): SIOUX (Niobrara R). VI-14 New county records.? BROWN: Plum Cr, Hwy 20 W Johnstown, 2000; Niobrara R, Hwy 183 S Springview, VI-13-2000, BCK; CHERRY: Niobrara R, Rt 61, VI-26-1996, BCK; DAWES: White R, 8mi NE Chadron, VI-17-1984, WPM; White R, Crawford, VII-6,VII-20-1984; White R, Slim Buttes, VII-17-1984; White R, Whitney, VII-20-1984, HRL; DUNDY: Re publican R, Rt 43W Bunckleman, VI-12-1994, Opler; FURNAS: Oxford at light, VIII-11-1982; Republican R, Oxford, VIII-11-1982, AVP; GARDEN: N Platte R, St Rt 27, VI-12-1994, BCK; HAYES: Frenchman R, Rt 16W Hamlet, VI-12-1994 BCK; KEITH: Ogallala at light, VI-22-1981, AVP; KEYA PAHA: Niobrara R, Hwy 183 S Springview, VI-13-2000, BCK; NANCE: Cedar R, St Rd 14 N Fullerton, VI-26-1998, BCK; NEMAHA: Auburn at light, VII-17-1995, THK; RICHARDSON: S Frk Big Nemaha R, St Rd 8,8 mi SW Humboldt, VII-21-1997, THK; SCOTTS BLUFF: N Platte R, Scottsbluff, VII-12-1989, BCK; SHERIDAN: Niobrara R, St Rd 27, VI-16 1984,WPM; Niobrara R, Gordon, VI-16-1984; Niobrara R, Peters, VII-27 1984; Niobrara R, VII-3,VIII-9,21-1984, HRL; THOMAS: Dismal R, Co Rd off Hwy 83,13.9 mi S Thedford; Mid Loup R, entrance Neb Nat For, 1mi W Halsey, VI-12-2000, BCK; VALLEY: Mid Loup R, Arcadia, VI-25-1998, BCK.

Isonychia sicca (Walsh) Previous reports.?Hamilton (1952): HARLAN (Republican City); MADISON (Norfolk). Traver (1935): LANCASTER (Lincoln). Klubertanz and Jones (1999): PAWNEE (N Frk Big Nemaha R). New county records.? DODGE: Elkhorn R, St Rd 91, 41/32/21N 96/ 27/15W, VI-5-2000, WPM; FURNAS: Republican R, Oxford & Oxford at light, VIII-11-1982, AVP; NEMAHA: Peru St Coll at light, Peru, VIII-2 1996, THK; SARPY: Platte R, St Rd 31,1 mi E Schramm Prk, VII-6-1996, THK; THOMAS: Dismal R, 13.9 mi S Thedford, VI-12-2000, THK; WHEELER: Cedar R, St Rd 70/91 E Ericson, 41/47/00N 98/41/53W, VI 6-2000, WPM.

LEPTOHYPHIDAE

Tricorythodes allectus (Needham) Previous reports.?Wiersema and McCafferty (2000): HOLT (S Frk Elkhorn R). New county records.? BROWN: Long Pine Cr, Long Pine St Rec Area, 42/23/37N 99/42/35W, VI-6-2000, WPM; FURNAS: Republican R, Ox ford, VIII-11-1982, AVP; LOUP: Calamus R, US Hwy 183,41 /56/49N 99/ 23/09W, VI-6-2000, WPM; PAWNEE: N Frk Big Nemaha R, 1mi E Table Rock, St Rd 4, IX-3-1997, THK; RICHARDSON: S Frk Big Nemaha R, St Rd 8 bridge, 8 mi SW Humboldt, VII-23-1997, THK. W. P. MCCAFFERTY ET AL. 23

Tricorythodes fictus Traver Previous reports.?Hamilton (1952): PLATTE (Columbus).

Tricorythodes minutus Traver state W New records: BROWN: larvae: Plum Cr, Hwy 20 Jownstown, VI-14-2000; Bone Cr, Keller Prk St Rec Area, 9.6 mi NE Ainsworth, Hwy 183, VI-13-2000, BCK; CHERRY: larvae, Niobrara R, Hwy 61, VI-14-2000, BCK; DAWES: adults and larvae: Niobrara R, below Box Butte Dam, VI 15-1984; Chadron Cr, Chadron St Prk, VI-10-1975,16,17-1984; White R, 8 mi NE Chadron at gravel rd, VI-17-1984, WPM; Bordeaux Cr, Cliffs, V 31,26,VI-13,VII-5,13,16,30,VIII-13-1984; Chadron Cr, V-31,VI-4,25,26,VII larvae: Niobrara 1,5,10,13,14,16,18,19-1984; R, Marsland, VI-1-1984; Pep per Cr, VII-10,25-1984; Saw Log Cr, VIII-16-1984; E Ash Cr, VI-4,26,VII 24-1984; Bordeaux Cr, Ricks, VII-16-1984; White R, Slim Buttes, VII-17 1984;White R, Ard Rd, VI-1-1984; White R, Crawford, VI-ll,VII-20-1984; White R, Ft Rob, VI-1-1984; Soldier Cr, VII-15-1984; adults: W Ash Cr, VII 16,VIII-6-1984, HRL; DAWSON: larvae, Platte R, Cozad, VI-7-1979, AVP; HALL: larvae, Platte R, St Rd 11 and 1-80, IV-26-1981, WPM; SIOUX: adults: Sowbelly Cr, Sowbelly Canyon 8 mi N Harrison, VI-14-1984, WPM; Niobrara R, Agate at light, VI-28-1984; larvae, Soldier Cr, VI ll,VII-6,20,VIII-2,IX-8-1984,HRL.

LEPTOPHLEBIIDAE

Leptophlebia cupida (Say) New state records: SIOUX: larvae, Soldier Cr, 6mi NW Fort Robinson, IV-19-1976, HRL.

Leptophlebia gravastella (Eaton) New state records: DAWES: larvae: Fort Robinson Area, 111-15-1979, Craft; Niobrara R, Marsland, VI-1-1984; Bordeaux Cr, IX-3-1977; E Ash Cr, X-29-1977; Chadron Cr, III-l 1-1978, HRL.

Leptophlebia nebulosa (Walker) Previous reports.?Hamilton (1952): DODGE (Fremont); HALL (Wood R); PLATTE (Columbus pond). Harris et al. (1999): SIOUX (Niobrara R). New county records.? CHERRY: Cottonwood L St Rec Area; N Loup R, Rt 83; Rt 20, 8 mi W Merriman; Bear Cr, Rt 20, 2 mi E Eli turnoff; Minnechaduza Cr, Crookston, V-23-1989, HRL; LOGAN: S Loup R, Rt 83, V-23-1989, HRL.

Neochoroterpes Oklahoma (Traver) New state records: GAGE: adult, Plum Cr, 8mi S St Rd 8 to Oketo, V 30-1997, THK; PAWNEE: larvae, Taylor Br, St Rds 4/65, Table Rock, V-21 1997, THK; RICHARDSON: subimago, Muddy Cr, Hwy 73, 1 mi W Verd?n, VIII-6-1996; adult, S Frk Big Nemaha R, St Rd 8, 8 mi SW Humboldt, V-21-1997, THK. 24 GREAT PLAINS MAYFLIES

Paraleptophlebia debilis (Walker) New state records: DAWES: larvae, Bordeaux Cr (Cliffs), X-28-1978, Craft.

Paraleptophlebia gregalis (Eaton) New state records: DAWES: larvae: Niobrara R, Marsland, IX-12 1978, Muenchau; Chadron Cr, VI-6-1979, HRL; SHERIDAN: larvae, Hay Springs Cr, V-29-1984, HRL. OLIGONEURIIDAE

Homoeoneuria ammophila (Spieth) Previous reports.?Carnevalo (1981): CHERRY (Niobrara R); KNOX (Niobrara R). New county records.?FURNAS: Republican R, Oxford R channel, VIII 11-1982, AVP; SHERIDAN: Niobrara R, VIII-9,21-1984; Niobrara R, S Gordon, VII-27-1984; Niobrara R, Gordon, VII-11-1984, HRL.

POLYMITARCYIDAE

Ephoron album (Say) Previous reports.?Traver (1935): DUNDY (Arikaree R); Hamilton (1952,1959): CHERRY (Snake R); DAWSON (Cozad); DUNDY (Rock Cr); FRONTIER (Curtis); SCOTTS BLUFF (Scottsbluff Canal); SIOUX (Uni versity L); Decker (1981): FRONTIER (Medicine Cr). New county records.? DAWES: White R, VIII-15-1984, HRL; FURNAS: Oxford at light, VIII-11-1982, AVP; GREELEY: Cedar R, St Rd 91,41/41/ 50N 98/25/23W, VI-6-2000, WPM; NEMAHA: Peru at light, VII-20-1997, THK; PAWNEE: N Frk Big Nemaha R, St Rd 4,1 mi E Table Rock, VIII-12 1997, THK; SHERIDAN: Niobrara R, St Rd 27, VI-16-1984, WPM.

Tortopus primus (McDunnough) Previous reports.?Hamilton (1952, 1959): BUFFALO (Kearney); DAWSON (Cozad); MADISON (Tri-County Canal). McCafferty (1975): WASHINGTON (Fort Calhoun). New records.? NEMAHA: Missouri county R, Peru, aquatic light trap, VII-21-1997, THK; RICHARDSON: S Frk Big Nemaha R, St Rd 8,8 mi SW of Humboldt, at light, VII-23-1997, THK. PSEUDIRONIDAE

Pseudiron centralis McDunnough Previous reports.?Hamilton (1952): PLATTE (Columbus). Decker (1981): DUNDY (Republican R); HITCHCOCK (Frenchman R, Republi can R); RED WILLOW (Republican R). Pescador (1985): LINCOLN (S Platte R).McCafferty and Provonsha (1986): no county indicated (Niobrara R). New county records.? BLAINE: N Loup R, Co Rd 1, VI-13-2000, THK; NEMAHA: Auburn at light, VII-8-1995; Peru St Coll at light, VI-21-1995, W. P. MCCAFFERTY ET AL. 25

THK; SHERIDAN: Niobrara R, St Rd 27, VI-15-1984, WPM; THOMAS: Dismal R, 13.9 mi S Thedford, VI-12-2000, THK; VALLEY: N Loup R, VI 25-1998, BCK;WHEELER: Cedar R, St Rd 70/91,41 /47/00N 98/41 /53W, VI-6-2000, WPM.

SIPHLONURIDAE

Siphlonurus columbianus McDunnough New state records: HALL: larvae, Platte R, St Rd 11/1-80, IV-26-1981, WPM.

Siphlonurus occidentalis (Eaton) Previous reports.?Decker (1981), Decker and Lunt (1982): DUNDY (S Frk Republican R); HITCHCOCK (Republican R).

ACKNOWLEDGMENTS

Funding for this research was provided in part by National Science Foundation Grant DEB-9901577 to WPM and Chadron State College Research Institute Grant 801-11-800-049 to RHL. The paper has been assigned Purdue Agriculture Research Program Journal No. 16393. LITERATURE CITED

Angle, L. 1987. Effects of sediment addition on the drift of aquatic in Nine Mile macroinvertebrates Creek, Nebraska. Unpublished Masters Thesis, University of Nebraska, Lincoln. A. F. W. P. 1979. Bednarik, and McCafferty. Biosystematic revision of the genus Stenonema (Ephemeroptera: Heptageniidae). Canadian Bulletin of Fisheries and Aquatic Sciences 201: vi + 1-73. Carnevalo, M. A. 1981. The ecology and distribution of Ephemeroptera (mayflies) along the Niobrara River system in northern Nebraska. Unpublished Masters Thesis, University of Nebraska, Omaha. M. A. S. R. Lunt. 1982. Carnevalo, and Abstract of "Ecology and in Distribution of mayflies the Niobrara River system in Nebraska." Proceedings of the Nebraska Academy of Science and Affiliated Societies 92: 9. P. O. and K. P Pruess. 1989. Effects of on of Darrow, substrate density in a aquatic southeast Nebraska stream. Transactions of the Nebraska Academy of Science 17: 19-22. Decker, M. L. 1981. The distribution and ecology of mayflies (Ephemeroptera) in the Republican River and its tributaries in Nebraska. Unpublished Masters Thesis, University of Nebraska, Omaha. M. L. and S. R. Lunt. 1982. Abstract of and Decker, "Ecology Distribu tion of mayflies in the Republican River system in Nebraska." Proceedings of the Nebraska Academy of Science and Affiliated Societies 92: 9. 26 GREAT PLAINS MAYFLIES

Hamilton, E. W. 1952. A taxonomic study of the Ephemeroptera of Nebraska. Unpublished Masters Thesis, University of Nebraska, Lincoln. Hamilton, E.W. 1959. Review of Ephemeridae (Ephemeroptera) in the Missouri River Watershed with a key to the species. Iowa State College Journal of Science 33: 443-474. B. f T. P. 1999. Harris, M. A., C. Kondratief and Boyle. Macroinvertebrate streams. Kan community structure of three prairie Journal of the sas Entomological Society 72: 402-425. Klubertanz, T. H and D. M. Jones. 1999. Adults of Camelobaetidius waltzi (Ephemeroptera: Baetidae) with field notes. Entomological News 110: 173-176. Kondratieff, B. C. and J. R. Voshell, Jr. 1984. The North and Central American species of Isonychia (Ephemeroptera: Oligoneuriidae). Transactions of the American Entomological Society 110:129-244. McCafferty, W. P. 1975. The burrowing mayflies of the United States. Transactions of the American Entomological Society 101: 447-504. McCafferty, W. P. 1991. Comparison of Old and New World Acanthametropus (Ephemeroptera: Acanthametropodidae) and other psammophilous mayflies. Entomological News 102: 205-214. McCafferty, W. P. 2000a. The gentle quest: 200 years in search of North American In: E. in in mayflies. Dom?nguez (ed.). Trends research Kluwer Ephemeroptera and Plecoptera. Academics/Plenum, New York. In press. McCafferty, W. P. 2000b. A new Nearctic Apobaetis (Ephemeroptera: Baetidae). Entomological News 111: 265-269. W. P. and A. V. Provonsha. 1986. McCafferty, Comparative mouthpart morphology and evolution of the carnivorous Heptageniidae (Ephemeroptera). Aquatic Insects 8: 83-89. P. R. P. a McCafferty, W. and Randolph. 1998. Canada mayflies: faunistic compendium. Proceedings of the Entomological Society of Ontario 129: 47-95. W. P. and R. D. Waltz. 1986. Baetis new McCafferty, magnus, species, new name for Baetis B of formal sp. Morihara and McCafferty (Ephemeroptera: Baetidae). Proceedings of the Washington Ento mological Society 88: 604. M. 1984. Moul, J. Prevalence and relationships of two allocreadiid Metacercariae in the burrowing mayfly, Hexagenia limbata (Serville in of Bluestem Guerin), Lake, Lancaster County, Nebraska. Trans actions of the Nebraska Academy of Sciences 12: 13-18. Pescador, M. L. 1985. Systematics of the Nearctic genus Pseudiron (Ephemeroptera: Heptageniidae: Pseudironinae). The Florida En tomologist 68: 432-444. T. F. 1974. Macroinvertebrates as indicators of water in Pesek, quality Salt Creek, Nebraska. Unpublished Masters Thesis. University of Nebraska, Lincoln. Provonsha, A. V. 1990. A revision of the genus Caenis inNorth America (Ephemeroptera: ). Transactions of the American Ento mological Society 116: 801-884. W. P. MCCAFFERTY ET AL. 27

A. V. W. P. 1985. new Nearc Provonsha, and McCafferty. Amercaenis: of tic genus of Caenidae (Ephemeroptera). International Quarterly Entomology 1: 1-7. Ratcliffe, B. C. 1990. Prairie, the Nebraska perspective. American Entomologist 36: 28-35. on Spieth, H. T. 1941. Taxonomic studies the Ephemeroptera. II. The genus Hexagenia. The American Midland Naturalist 26: 233-280. A. 1967. Factors Swanson, G. influencing the distribution and abun dance of Hexagenia nymphs (Ephemeroptera) in a Missouri River Reservoir. Ecology 48: 216-225. R. Part 239-739. In: Traver, J. 1935. II, Systematic. Pages J. G. Needham, R. a J. Traver, and Y.-C. Hsu. The biology of mayflies with system atic account of North American species. Comstock, Ithaca, New York. N. A. W. P. Wiersema, and McCafferty. 2000. Generic revision of the North and Central American Leptohyphidae (Ephemeroptera: Transactions of the American Pannota). Entomological Societ, in press.

Table 1. North American distributions of Nebraska mayflies relative to = = = = = Nebraska. N north, NE northeast, E east, SE southeast, S south, = = = SW southwest, W west, NW northwest.

Species N NE E SE S SW W NW

Acentrella ampia X X X X Acentrella insignificans XXX X X X X Acentrella p?rvula X X X X X Acentrella t?rbida X X X X X X X Acerpenna pygmaeaX X X X X X Amercaenis ridens XXX

Apobaetis lakota X Baetis flavistriga X X X X X X Baetis intercalaris X X X X X Baetis magnus XXX Baetis tricaudatus XXXXXXXX Baetisca lacustris X X X X X XX Brachycercus edmundsi X Brachycercus nasutus X X Brachycercus prudens X XXX X Caenis arnica XXXXXXXX

Caenis bajaensis XXX Caenis hilaris X X X X

Caenis latipennis XXXXXXXX Caenis tardata XXX X X Caenis youngi XXX XXX Callibaetis ferrugineus XXX X X X X Callibaetis fluctuans X X X X X X Callibaetis pallidus XXX XXX Callibaetis pictus X XXX Camelobaetidius variabilis X 28 GREAT PLAINS MAYFLIES

Camelobaetidius waltzi X X Camelobaetidius warreni XXXX

Centroptilum album XXX XX Centroptilum bifurcatum X XX convexum Centroptilum XXX Cercobrachys serpentis X Diphetor hageni X X X X X XX Ephemerella aurivillii XXX XX Ephemerella inermis XXX X X X Ephoron album XXXXXXXX Fallceon quilleri X X X X X X Heptagenia diabasia X X X X X X Heptagenia elegantula X X X X X Heptagenia flavescens X X X X X X X Hexagenia bilineata X X X X X X X Hexagenia limbata XXXXXXXX Homoeoneuria ammophila X X Isonychia bicolor X XX X Isonychia rufa X X X X X X Isonychia sicca X X X X X X Leptophlebia cupida X X X X X X X Leptophlebia gravastella X X Leptophlebia nebulosa X X X X X XX Leucrocuta hebe X X X X Leucrocuta maculipennis X X X X X X Macdunnoa persimplex XXX X Neochoroterpes Oklahoma XXX Paracloeodes minutus X X X X X X

Paraleptophlebia debilis XXXXXXXX Paraleptophlebia gregalis X X Pentagenia vittigera X X X X X Plauditus dubius X X X X X Plauditus punctiventris X X X X XX Procloeon rufostrigatum X X X X X Pseudiron centralis X X X X X X X Pseudocloeon dardanum XXXX Pseudocloeon frondale X X X X X

Pseudocloeon longipalpus X X X X Pseudocloeon propinquum XXXXXXXX Raptoheptagenia cruentata XXX X Siphlonurus columbianus X X Siphlonurus occidentalis X X X X Stenacron interpunctatum X X X X X X Stenacron minnetonka X X

Stenonema exiguum X X X X Stenonema femoratum X X X X X X Stenonema mexicanum X X X X Stenonema modestum X X X X Stenonema pulchellum X X X X X Stenonema terminatum X X X X X XX Stenonema vicarium X X X X X X Tortopus primus X XXX Tricorythodes allectus X X X Tricorythodes fictus X X Tricorythodes minutus XXXX X X X ._^? KEYAPAHA ~* I /i j ^^BOYDj \^^ JL?J*** L

DAWES ill! , \ ^?"^ i i ! v r-^|H,? _/ i ?CMXOnS^ i i t KNox i t,tuft r^^#* PIERCE ?n j "? ? ROCK ^^V ! !_._i?-K ^J ' ?' "^ ?ANTELOPEJ ^ S'OUX SHERIDAN ? WA Y N E < URST?Nt "^ 'BOX BUTTE*' | CHERRY ^""N^ '?X.'? l^? ?

MORRILL > ! W-1I'A - ^^\ ' ? -^*/> ^"N^k N>1 V? \ S ^ ! I I ?X. I iniiD NvGARFCLDV^ 1 BOONE'MAD,S0N'STANTON? CUMING~ ! f) I SCOTTSBLUFFJ ! GARDEN ! GRANT HOOKER?THOMAS BLAINE L0U-E^>K jVl 't_i-7-U T "ATJ-?_ X v PLATTE ^-Washington H -><**, L0GA ! ?colfaxI' V--+-J-r--A--r-N^TtX'*;^^.i ^<1! ! ^-^A. V^ TS>. 1 dodge\ g V BAMWCD * ' ' ' CUSTER j .-JV?-4 3 ARTHURJ ^-V PHERSON, --l \vALLe71g?EELEY, V--'--^^ ? -"*!* "" -~N^ JMC V_ _\_[NAM?E^fcC^jPfcU^ \dOUGLAsT S ? * ^^^?V ? BUFFALO! ^^i HAMILTON! YORK !sEWARD? |"~ ?> X X*^ PERKINSI I' ^yj^~?'_1-?-1 P"""1' 1 -rJ-.-J--1-^- r^T^~ I I IIAMTASTER1OTOE . V CHASE I FRONTIER Platte' ? HAYS I I J i |!^f2?l,Sl-,-\ . ? I I J 11 | II ?JOHNSON! \ " ! ! ! . ^^^5r ?-gosperUhelps *?!my^^^^?WEBSTER. j^k L J jOAQEf ~0?NTY""^^^^JrR?bw.LLOwj:-^h'aRLAnTf^un ' ' j .pAWNEElRICHARDSON \ \^S>-\^^r^Fa'1Rt ^V ! ! SJEFFEBS0N? ^?NAS ^^^-*t~~^! {THAYERj-j-_ /^Th^cock! j

FIGURE 1. stream m Nebraska counties and major systems. 30 GREAT PLAINS MAYFLIES