J. New YorkEntomol. Soc. 102(2):261-265, 1994 A NEW SPECIES OF AMBRYSUS STAL FROM ASH MEADOWS, NEVADA (HETEROPTERA: NAUCORIDAE) John T. Polhemus and Dan A. Polhemus University ofColorado Museum, 3115 S. York, Englewood, Colorado 80110, and Department ofLife Sciences, Bishop Museum, P.O. Box 19000A, Honolulu, Hawaii 96817 Abstract.—Ambrysus relictus, n. sp. is.described from thermal springs in Ash Meadows, Nevada, andcomparedtoAmbrysusamargosusLa Rivers, anotherthermallyendemicspecies occurringinthesamearea. Thewarm springhabitatofthespeciesisdiscussed,andfiguresare provided ofthe dorsal habitus, male abdominal terminalia, and female subgenital plate. The biota ofAsh Meadows, a spring fed desert oasis lying in the Amargosa River basin approximately 90 miles northwest ofLas Vegas, Nevada, has longbeen noted for its high concentration ofendemic plants, fishes, snails and aquatic insects. The thirty thermal seeps and springs that emerge in this area harbor the most diverse localassemblageofendemicspeciesfoundanywhereinthecontinentalUnitedStates, including the naucorid Ambrysus amargosus La Rivers, which is confined to Point ofRock Springs (La Rivers, 1953), nearthe southern end ofthe oasis. In early 1991 itwas brought to ourattentionby DougThreloff, the biologistfortheAsh Meadows National Wildlife Refuge, that a second population ofnaucorids was present in a group ofsprings further to the north. These insects proved to be a new species, and are described herein as Ambrysus relictus. The discovery ofthis taxon brings the number of thermally endemic Ambrysus known to occur in the Amargosa River system to three, including the aforementioned A. amargosus, plus A. funebris La Rivers, which is found in thermal outflows near Furnace Creek, in Death Valley. In the description below all measurements given are in millimeters. Specimen repositories are given in the acknowledgments. Ambrysus relictus, new species Figs. 1-3 — Description. Small, ovate, brachypterous, shapeasinFigure 1. Length, male 5.34 mm (mean, N = 10; min. 5.16, max. 5.66), female 5.44 mm (mean, N = 10; min. 5.22, max. 5.72);width, male 3.30mm(mean,N= 10; min. 3.11, max. 3.50), female 3.44 mm (mean, N = 10; min. 3.22, max. 3.88), widest across embolium. Groundcoloryellowish,withstronglycontrastingdarkmarkingsondorsum;faintly shining, head and pronotum shallowly rugulose, pronotum punctate; scutellum and hemelytra thickly set with white punctations; head medially and posteriorly brown; pronotumbroadlyyellowishtoluteousonlateralmarginsandentireposteriormargin; 262 JOURNALOFTHE NEWYORKENTOMOLOGICALSOCIETY Vol. 102(2) scutellum dark medially; hemelytra with embolium light on anterior % to 3A, light wedge-shaped mark present on inner corium at junction of membrane and outer corium, scattered light markings present on corium and clavus. Venter yellowish, tinged with brown; legs yellowish, spines brown. Head narrow, deeply set into pronotum, produced anteriorly for ofeye length, anteclypeal margin almost straight; vertex very slightly domed medially, produced behindeyes for Vi ofeye length, with numerous short setae laterally alongandahead ofeyes; length 1.00, width through eyes 1.44. Eyes with many ommatidia, twice as long as wide, with narrow lateral flange; embraced posteriorly by pronotum; length 0.55, width 0.28, posterior/anterior interocular space 0.69/0.89. Eyes not raised, almost flat dorsally, forming smooth transition to head; labrum broad, rounded; maxillary plates not prominent. Pronotum slightly domed, lateral margins slightly convex, smooth, set with long silky setae (often appressed); posterior margin broadly demarcated by weak sulcus; humeral angles obtuse, not sharp; maximum length 1.66, length on midline 0.94, width 2.89. Scutellum triangular, not raised, roughly twice as wide as long, length 0.72, width 1.55. Hemelytra long, fully developed, reaching almost to posterior marginofabdomen;emboliumweaklyexpanded,notsinuateposteriorly.Hindwings reduced, costal cell present. Connexival margins oftergites II—III (first two visible) smooth, IV-VI weakly serrate; posterolateral angles weakly spinose. Ventral surface sparsely set with short appressed setae; propleura not contiguous with prostemum; propleura touching medially, separated there from mesostemum. Fore femur broad, length/width = 1.28/0.89; tarsi reaching to adjacent proximal part offemur. Middle and hind femora slender, each with two closely set rows of smallyellowishspinesonposteriorsurface, oneroweachatdorsalandventraledges; middle and posterior tibia with numerous stout spines, distally with two transverse rows ofsmaller spines. Male and female abdominal terminalia and genitalia as in Figures 2 and 3. Holotype, brachypterous male: NEVADA, Nye Co., South Scruggs Spring, Ash Meadows NWR, 710 m, water temp. 33°C, CL 2715, 22 July 1992, J. T. and D. A. Polhemus (USNM). Paratypes, all brachypterous, all from NEVADA, Nye Co., collected by J. T. and D. A. Polhemus unless otherwise noted: 7 males, 10 females, 3 nymphs, same data asholotype(USNM,JTPC); 9 males, 4females,NorthScruggsSpring,AshMeadows NWR, 710 m, water temp. 33°C, CL 2714, 22 July 1992; 4 males, 1 female, Marsh Spring, Ash Meadows NWR, 710 m, water temp. 31°C, CL 2716, 22 July 1992; 1 male, 1 female, NorthIndianSpring,AshMeadowsNWR, 710 m,watertemp. 31°C, CL 2717, 22 July 1992 (all JTPC, USNM); 9 males, 8 females, Scruggs Ranch, B. Y.U.-A.E.C. (Mercury,NevadaN.T.S.),collectorunknown, 15 March 1962(USNM); 7 males, 8 females, North Scruggs Spring, Ash Meadows NWR, 27 March 1992, R. S. Zack & K. A. Rosema (WSUC); 9 males, 4 females, Marsh Spring, Ash Meadows NWR, 27 March 1992, R. S. Zack & K. A. Rosema (WSUC); 1 male, 1 female, 4 nymphs, Scruggs Spring, Ash Meadows NWR, WDS-A-911, 8 August 1992, W. D. Shepard (WSUC); 3 males, 2 females, 10 nymphs, Indian Spring, Ash Meadows NWR, WDS-A-910, 8 August 1992, W. D. Shepard (WSUC). Etymology.—The name relictus refers to the relictual nature ofthis warm spring endemic. Masculine. 1994 A NEWAMBRYSUSFROM ASH MEADOWS 263 Figs. 1-3. Ambrysus relictus, n. sp. 1. Dorsal habitus. 2. Female abdominal terminalia, ventral view. 3. Male abdominalterminalia, dorsal view. 264 JOURNALOFTHE NEWYORKENTOMOLOGICALSOCIETY Vol. 102(2) DISCUSSION A. relictus, n. sp. differs fromA. amargosusLa rivers in the followingrespects: the maleprocessisabsent,withthesixthmaletergitedifferentlyformed,havingnoangle or posterior protuberance as in amargosus (Fig. 3); the female subgenital plate is almostsymmetrical,versusquiteasymmetricalinamargosus, andisnotchedapically as in amargosus, but with a slightly different shape along the posterior margin (Fig. 2); the body is smaller and narrower than amargosus', the head is more strongly produced posteriorly than amargosus', and the connexival margins of relictus are smooth on tergites II—III (first and second visible segments) and weakly serrate on IV-VI,versusstronglyserrateon IV-VI inamargosus, andnon-serrateinA.funebris La Rivers. This set ofcharacter states would place relictus in the Ambrysuspudicus group ofLa Rivers (1953:89). The speciation ofAmbrysus in isolated warm springs throughout the Amargosa RiverdrainageofsouthernNevadaandtheadjacentDeathValleyregionofCalifornia parallels a phenomenon well documented for the desert pupfishes (Williams et al., 1985).A. relictus, n. sp. isthe thirdthermallyendemicAmbrysusspeciesnowknown fromtheAmargosasystem;thespringhabitatsoftheothertwospecies,A. amargosus and A.funebris, were discussed by La Rivers (1949, 1953). HABITAT Ambrysus relictus occurs in a closed basin containing five warm springs: North ScruggsSpring, SouthScruggsSpring, Marsh Spring, NorthIndianSpringandSchool Spring. All ofthese springs are small thermal outflows with shallow runs less than onemeteracross. The insectswere foundin open reachesthatwerenotcoveredover withvegetation,andhadamarlybottomsubstrateofpartiallycementedstones,small pebbles and gravel. Both North and South Scruggs Springs have substantial popu- A lationsof relictus, whileMarshandNorthIndian Springsappeartoharborsmaller populations. A. relictus is apparently absent from School Spring, possibly because this spring was seriously disturbed by previous owners. The spring complex containingA. relictus is approximately five kilometers north ofPoint ofRock Springs, a tightly clustered set ofthermal outflows harboring the endemicAmbrysus amargosus La Rivers. This lattertaxon has experienced extreme population declines over the past forty years due to habitat alterations associated with waterdevelopment, and is the only aquaticinsectpresently heldon the Federal Register, where it is listed as threatened. The current status ofA. amargosusand the historyofitsdeclinewasrecentlyreviewedbythejuniorauthor(Polhemus, inpress). Although currently abundant, A. relictus must also be considered potentially at risk, since it occurs in a similarly limited thermal spring ecosystem. The springs containingA. relictus have been designatedas “Desert Pupfish Habitat” by the U.S. Fish and Wildlife Service, since theycontain an endemic pupfish in addition to the naucorids, and this should in principle confer the species’ habitat some degree of protection. Because ofthe restricted distribution ofA. relictus, consideration should be given to it in future decisions concerning resource management activities and planning. 1994 A NEWAMBRYSUSFROM ASH MEADOWS 265 ACKNOWLEDGMENTS Wearedeeplygrateful to DougThrelofFforcallingourattention to thisremarkable species, for assistance in the field, and for stimulating discussions on naucorid distribution in the southern Great Basin. We also are indebted to Richard Zack, Washington State University, Pullman (WSUC), R. C. Froeschner, National Museum ofNaturalHistory, Washington, D.C. (USNM), and W. D. Shepard, Sacramento, CA (WDSC) forthe loan ofspecimens. LITERATURE CITED La Rivers, I. 1949. A new species ofAmbrysus from Death Valley, with notes on the genus in theUnited States (Hemiptera: Naucoridae). Bull. S. Cal. Acad. Sci. 47:103-110. La Rivers, I. 1953. New gelastocorid and naucorid records and miscellaneous notes, with a descriptionofthenewspecies,Ambrysusamargosus(Hemiptera:Naucoridae).Wasmann J. Biol. 11:83-96. Polhemus, D. A. In press. Conservation of aquatic insects: worldwide crisis or localized threats?Am. Zool. Williams,J. E., D. B. Bowman, J. E. Brooks, A. A. Echelle, R. J. Edwards, D. A. Hendrickson and J. J. Landye. 1985. Endangered aquatic ecosystems in North American deserts with a list ofvanishing fishes ofthe region. J. Arizona-NevadaAcad. Sci. 20:1-62. Received 10 November 1993; accepted 29 January 1994.