Six new species of Nirridessus Watts and Humphreys and Tjirtudessus Watts and Humphreys (Coleoptera: Dytiscidae) from underground waters in Australia

18 Pages·2000·6.3 MB·

by  C H S Watts

SIXNEW SPECIES OFNIRRIDESSUS WATTS AND HUMPHREYS AND
TJIRTUDESSUS WATTS AND HUMPHREYS (COLEOPTERA: DYTISCIDAE)
FROM UNDERGROUND WATERS INAUSTRALIA
C. H. S. WATTS AND W. F. HUMPHREYS
WATTS, C. H. S. and HUMPHREYS, W. F. 2000. Six new species ofNirridessus Watts and
Humphreysand TjirtudessusWattsandHumphreys (Coleoptera: Dytiscidae)fromunderground
waters inAustralia. Recordsofthe SouthAustralian Museum33(2): 127-144.
Six new species(Nirridessusbigbellensis, N. cueensis, N. hinkleri, N. morgani, Tjirtudessus
hahni and T. magnificus) of stygobiontic beetles of the family Dytiscidae, subfamily
Hydroporinae, tribe Bidessini, from relatively shallow, calcrete aquifers in Western Australia,
aredescribed and figured. The species are members ofadiverse, recently discovered, relictual
stygofauna, predominantly of Crustacea and Oligochaeta, inhabiting calcretes lying along
palaeodrainagechannels. The twogeneraoccur in palaeochannel deposits on either sideofthe
divide between the inland and Indian Ocean drainages. Each calcrete area contains a distinct
assemblageofbeetles andthefaunaoccurs in bothfresh and salinegroundwater. Thephysico-
chemical properties ofthe groundwater, and the palaeogeography andhydrology oftheregion
arediscussedin somedetail.
C. H. S. Watts, South Australian Museum, North Terrace, Adelaide, South Australia5000. W.
F. Humphreys, Western Australian Museum, Francis Street, Perth, Western Australia 6000.
Manuscriptreceived 11 October 1999.
Stygobiotic water beetles have been reported Methods
from a number of widely scattered localities
around the world (Spangler 1986) but it was not About 120 sites were sampled, comprising
until 1999 that they were first reported from pastoral wells and boreholes constructed for water
Australia (Watts and Humphreys 1999). These abstraction, groundwater investigation and
belonged to the Dytiscidae and were discovered mineral exploration in anumberoffractured rock,
living in relatively shallow calcrete aquifers in the alluvial and groundwater calcrete aquifers from
Lake Way/Lake Carey palaeodrainage system of the central Yilgarn Craton of Western Australia
Western Australia. Five species in three genera in (Fig. 38). The beetles and associated fauna were
thetribeBidessini were involved. taken by plankton nets hauled through the water
These groundwater calcretes are restricted to column ofthe bores and wells, or sometimes from
the arid parts of Australia (Fig. 40) where the baitedtraps.
potential evaporation exceeds rainfall by more Physico-chemical parameters in the water were
than an order of magnitude (detailed in determined either in situ, or in a sample taken
Humphreys 1999; Watts and Humphreys near the surface using a bailer, using electronic
— WTW
1999). instruments pH using a pH 320 meter
In May 1999 one of us (W.F.H.) spent some with a SenTix 97T pH combined electrode with
time investigating other areas of inland integrated temperature sensor and redox probe,
WTW
palaeodrainage in Western Australia with and dissolved oxygen using a Oxi 320
groundwater calcretes and discovered additional meter and a CellOx 325 oxygen sensor
stygofaunas whichincludeddytiscids. (Wissenschaftlich-Technisch Werkstatten GmbH,
In this paper we describe the six species of Weilheim, Germany). Conductivity was measured
Dytiscidae collected and record the existence ofa with aTPS Model LC 84 conductivity meter (TPI
further two, all belonging to two of the original Electronics, Springwood, Queensland, Australia).
genera: Tjirtudessus and Nirridessus. We also All were calibrated as specified using the
give details ofthe physico-chemical properties of recommended standards. In some samples the
the water in the aquifers and the palaeogeography salinity was determined using a hand
and hydrology oftheregion. refractometer(Atago S-lOe).
128 C. H. S. WATTS&W.F. HUMPHREYS
Abbreviations used Length => 3.0 mm; eye remnant present
WAM
BES Prefix for field numbers, (Fig. 5); groupofsixspinesclosetobase
Biospeleology. ofmesofemuronhindedge (Fig. 11) ....
OB Observation bore. — N. bigbellensis sp.nov.
PAT Prefix, observation bore number, Austin Length =< 2.5 mm; with or without eye
Downs Borefield, Big BellMine. remnant;spinesonmesofemurspreadout
SB Prefix, piezometer number in Hinkler along hind edge or, ifrestricted to base,
Wellcalcretetothe westofLakeWay. fourorfewer(Figs8, 9, 13, 15) 6
—
TPB Prefix, piezometer number in Hinkler 6. Pro-andmesotarsibroad(Fig.4);segments
Wellcalcreteto the westofLakeWay. twoandthreeofantennaesimilarinshape;
SAMA South Australian Museum, Adelaide. apical lobe of paramere overlies part of
WAM WesternAustralian Museum, Perth. restofparamere (Fig. 34)
N. cueensis sp.nov.
- Pro- and mesotarsi only weakly expanded
Systematics (Fig. 3); segments two and three of
antennaedifferentinshape, secondbroad
KeyToAustralian SpeciesOfStygobionic androunded,thirdnarrowandtriangular;
Bidessini apical lobe of paramere well separated
— from restofparamere (Fig. 35) 7
1. Bordeytilceulnagtteh,<l1e.g2smsmto,utd,orwsiatlhsouurtfascweismtmrionnggl-y - Elytronwithoutsubsuturalrowofpunctures;
hairson foreand midlegs metatrochantersbluntlypointed(Fig. 14);
KintingkakurutjutuWatts& Humphreys lengthapproximately1.5mm;medianlobe
—
Body length >1.2 mm, dorsal surface with ofaedeagus truncated(Fig. 35)
weaktomoderatereticulation,legsnormal, N. hinklerisp.nov.
all legs with swimminghairs 2 - Elytron with row of large subsutural
—
punctures; metatrochanters rounded;
2. Pronotumusuallywiderthanelytra(Fig. 1);
thirdandfourth(apical)segmentsoflabial length up to 2.5mm; median lobe of
palpi subequal in length (Figs 23-25); aedeagus pointed 8
setae on hind edge of mesofemur not 8. - - Length 2.2-2.3 mm; witheyeremnant
greatlydifferentinrobustnessfromthose ..N. windarraensisWatts & Humphreys
onmesotrochanter(Figs10,19,20).Length - Length 1.3-1.5 mm; withouteyeremnant
— > 3.0 mm (Tjirtudessus) 9 N. lapostaaeWatts & Humphreys
Pronotumsamewidthornarrowerthanelytra Q - Pro- andmesotarsi stronglyexpanded(Fig.
(Figs 3-6); third segmentsoflabial palpi
halfto two thirds length of apical (Figs 1); apical five segments of antennae
26-32); setaeonhindedgeofmesofemur noticeablythinnerthanothers (Fig. 1)...
nearbasemuchmorerobustthanthoseon T. magnificus sp. nov.
mesotrochanter or elsewhere on femur - Pro-andmesotarsionlymoderatelyexpanded
(Figs 7-9). Length 1.0-3.2mm (Fig. 2);apicalfivesegmentsofantennae
(Nirridessus) 3 not narrowerthanothers (Fig. 2) 10
— -
3. — Pronotalplicae wellmarked 4 10. Length>4.0mm; medianlobeofaedeagus
Pronotal plicaedifficulttotrace 5 twisted,tipknobbed(Fig.37);withouteye
—
4. Length of metatarsal segments 1 & 2 > remnant; pronotum at its base a little
segments 3 & 4; eye remnant present; narrowerthanelytra(Fig. 2)
parameres withlong apical lobe - T. hahnisp. nov.
N. pulpaWatts&Humphreys Length<4.0mm; medianlobeofaedeagus
—
Length of metatarsal segments 1 & 2 = < not twisted, tip pointed; with small eye
segments 3 & 4; without eye remnant; remnant; pronotum at itsbase widerthan
paramereswithsmallapicallobe(Fig.33) elytra
N. morgani sp. nov. T. eberhardiWatts&Humphreys
NIRRIDESSUSAND TJ1RTUDESSUS 129
FIGURES 1-6. 1,DorsalviewofTjirtudessusmagnificus;2,ditto T. hahni;3,dittoNirridessushinkleri;4,dittoN.
cueensis;5,dittoN. bigbellensis; 6,dittoN. morgani. Scalebar= 1mm.
Tjirtudessus Watts & Humphreys, 1999 bore, 27°16'10"S, 117°59'23" E, 12/5/99, coll W.
T-,Jj..ir.tudessus magonifjwi.cus spk. nov. rF.egiH,s,utrmapt'hiornenyJusmb&,erH.2„6,8J„.4.0.H.ahn',' in sp^irit, WAM,
Type* Paratype: f. BES 7066, same data as for
Holotype: m. 'BES 7040, OldCue watersupply holotypeexcept 13/5/99, SAMA.
130 C. H. S.WATTS&W.F. HUMPHREYS
Description (numberexamined, 2) Figs 1, 19, 20, and second ventrites fused, sutural lines distinct,
25, 36. ventrites three to five mobile, moderately covered
Habitus: Length 4.7-4.8 mm.; relatively flat, with small seta-bearing punctures, ventrites three
strongly constricted at junction of pronotum/ and four with a long central seta orbunch oflong
elytra; uniformly light testaceous; hindwing setae.
vestigial, abouthalflengthofelytron (Fig 1). Legs: Protibia relatively narrow, inner edge
Head: Large, nearly as wide as elytra; smooth, straight, outer edge bowed, widest past middle
reticulation very fine, punctures sparse, weak; where it is about three times its basal width;
subparallel in posterior half; sides with dark protarsi greatly expanded, first segment very
suture in middle near anterior edge. Antenna broadly oval, second segment broad about one
relatively stout, basal two segments cylindrical, third length offirst, third segment as long as first
third segment longer and narrower at base, next but much narrower and very deeply bifid, fourth
three subequal, next four progressively thinner, segment very small and hidden within lobes of
apical segment a bit longer and much narrower third segment, apical segment narrow,
than penultimate, each segment with some very cylindrical, about length of third, segments one
small setae on inside apically (Fig. 1). Maxillary to three with very dense covering of adhesive
palpus thin, elongate, apical segment large, a little setae; claws short and simple. Mesotrochanter
shorter than segments one to three combined, rounded with row of setae on inner edge;
three long setae on outer side and some sensillae mesofemur with row of 10-12 relatively weak
towards tip, tip truncated. Labial palpus moderate, setae along hind edge in basal half (Fig.19);
apical two segments subequal, tip weakly bifid, mesotarsi similar to protarsi. Metatrochanter
penultimate segment with small papilla near tip weakly pointed (Fig. 20); metafemur elongate,
bearingtwo setae (Fig. 25). lacking spines; metatibia strongly curved,
Pronotum: Very broad, wider than elytra (Fig. widening towards apex; metatarsi elongate, basal
1); anterolateral angles projecting strongly segment longest, apical segment a little longer
forward; base quite strongly narrowed, than fourth, segments one and two in
posterolateral angles acute; smooth, with sparse, combination about as long as others; claws weak.
very weak punctures and a row of stronger Male: Antennae a little stouter; pro- and
punctures along front margin; basal plicae weak, mesotarsi a little stouter. Median lobeofaedeagus
reaching to about half way along pronotum, narrow, narrowing rapidly in apical quarter;
slightly excavated inwards; with row oflong setae paramere broad, apical segment with pronounced,
laterally, densertowards front. narrow, apical lobe (Fig. 36).
Elytra: Not fused, lacking inner ridges;
elongate, widest behind middle, smooth, quite Etymology
densely and evenly covered with very small The species is named in reference to its
punctures, row of widely spaced larger punctures appearance.
close to inner edge; lacking setiferous
micropunctures; row of long setae near lateral Remarks
edge, a few additional larger punctures with long A very large broad flat Tjirtudessus readily
setae, more frequent towards sides. Epipleuron recognised by the large round first segment ofthe
broad in anterior fifth, then rapidly narrowing to pro- and mesotarsi of both sexes, and the
be virtually absentoverrestofelytron. distinctive antennae with the apical segments
Ventral surface: Prothoracic process relatively noticeably narrowerthan themiddle segments.
broad, strongly narrowed between coxae, not
reaching mesothorax, apical half spatulate,
strongly arched in lateral view with highest point Tjirtudessus hahni sp. nov.
(viewed ventrally) between coxae. Mesocoxae in
contact at midline. Metathorax sharply triangular Types
in front in midline, wings very narrow, broadly Holotype: m. 'BES 7197, mineral exploration
rounded in midline behind. Metacoxal plates bore, 26°41'16"S, 120°17'52"E, 21/5/99, coll. W.
large, metacoxal lines short, weak, widely spaced, F. Humphreys & H. J. Hahn\ slide mounted,
reaching to about halfway to metasternum, WAM, registration number 26887.
diverging in anterior two-thirds; moderately Paratypes: 4; same data as holotype, most
covered with small setae-bearing punctures; incomplete, 2 slide mounted, SAMA, 2 in spirit,
closely adpressed to first abdominal ventrite. First WAM, registration numbers 26841, 26842.
NIRRIDESSUSAND TJIRTUDESSUS 131
Description (numberexamined, 5) Figs2, 21, 22, uniformly light testaceous; hindwing vestigial,
24, 37. aboutone-thirdlengthofelytron (Fig. 2).
Habitus: Length4.8 mm.;relatively flat, strongly Head: Large, smooth, reticulation very fine,
constricted at junction of pronotum/elytra; punctures sparse, weak; subparallel in posterior
%^^
(
FIGURES 7-32. 7,Ventral viewofmesotrochanterandraesofemurofNirridessuspulpa;8,dittoN. windarraensis;
9, ditto N. lapostaae; 10, ditto Tjirtudessus eberhardi; 11-12, ventral views ofmesotrochanterand mesofemurand
metatrochanterandmetafemurofN. bigbellensis; 13-14,dittoN. hinkleri; 15-16, dittoN. cueensis; 17-18, dittoN.
morgani; 19-20ditto T. magnificus; 21-22, ditto T. hahni; 23,labial palpusofT. eberhardi;24, ditto T. hahni; 25,
ditto T. magnificus: 26, ditto N. bigbellensis; 27, ditto N. hinkleri; 28, ditto A', morgani; 29, ditto N. cueensis; 30,
dittoN. windarraensis;31,dittoN. lapostaae;32,dittoN. pulpa.
132 C. H. S.WATTS&W. F. HUMPHREYS
half; sides withdarksuture in middle nearanterior coveringofadhesivesetae, clawsrelatively strong,
edge. Antenna stout, basal two segments largest, simple. Mesotrochanter parallel-sided broadly
next six segments narrower at base, subequal, triangular at apex with a few setae on inner edge,
segment six the widest, apical segment twice as mesofemur with a row of five to six relatively
long as penultimate (Fig. 2); each segment with weak setae alonghind edge inbasal half(Fig. 21);
some very small setae on inside apically. mesotarsi more elongate than protarsi.
Maxillary palpus relatively thin, elongate; apical Metatrochanter curved on outer edge straight on
segment largest, some sensillae towards tip, tip inner edge (Fig. 22), metafemur elongate, sinuate
weakly bifid. Labial palpus not particularly thin; (Fig. 22), metatibia weakly curved, widening
apical two segments subequal; tip weakly bifid; towards apex; metatarsi elongate, basal segment
penultimate segment with two setae near apex longest, apical segment a little longer than fourth,
arisingfromslightbulge (Fig. 24). segments one and two in combination about as
Pronotum: Broad, a little narrower than elytra long as others; claws weak.
(Fig. 2); anterolateral angles projecting strongly Male: Antennae and tarsi as in female. Median
forward; base quite strongly narrowed; lobe of aedeagus narrow, twisted slightly,
posterolateral angles acute; smooth, punctures knobbed at apex; paramerebroad, two-segmented,
sparse, very small, a row of stronger punctures apical segment with pronounced, narrow, apical
along front margin; basal plicae short, very weak, lobe (Fig. 37).
only visible in some lights; row of long setae
laterally, densertowards front. Etymology
Elytra: Not fused; lacking inner ridges; This species is named after Hans Jurgen Hahn
elongate, widest behind middle. Elytron smooth, who assisted with describing the physicochemical
quite densely and evenly covered with small environmentoccupiedby the stygofauna.Thetype
punctures each with a small seta, row of widely locality is an excellent example of this kind of
spaced larger punctures close to inner edge; some habitat.
setiferous micropunctures at base, near suture and
near apex; row of long setae near lateral edge, a Remarks
few additional long setae, more frequent towards T. hahni resembles T. magnificus in its large
sides. Epipleuron broad in anterior fifth, then size and broad body but differs in its much less
rapidly narrowing to be virtually absent over rest expanded pro- and mesotarsi and in its more
ofelytron. normal antennae which have segments 5-10
Ventral surface: Prothoracic process relatively subequal in size. It can be separated from both T.
broad, strongly narrowed between coxae, not magnificus and T. eberhardi by the median lobe
reaching mesothorax, apical half spatulate, tip of the aedeagus which is noticeably twisted and
rounded, strongly arched in lateral view with has a rounded knob at the tip and by its pronotum
highest point (viewed ventrally) between coxae. which, unlike in those species, is a little narrower
Mesocoxaemeet. Metathorax sharply triangularin than theelytra.
front in midline, wings very narrow, broadly
rounded in midline behind. Metacoxal plates
&
large; metacoxal lines short, weak, widely spaced, Nirridessus Watts Humphreys, 1999.
almostobsolete; punctures very sparse, very weak;
closely adpressed to first abdominal ventrite. First Nirridessushinkleri sp. nov.
and second ventrites fused, sutural line virtually
obliterated, ventrites three to five mobile, Types
moderately covered with small seta-bearing Holotype: m. 'BES 7134, SB 32/1, 26°52'31"S,
punctures, ventrites three and four with a long 120°12'05"E, 17/5/99, coll. W. F. Humphreys &
central setaorbunch oflong setae. H. J. Hahn', slide mounted, WAM, registration
Legs: Protibia moderately broad, inner edge number 26843.
straight, outer edge bowed, widest past middle Paratypes: 58, samedataas holotype, 29 WAM,
where it is about three times its basal width; registration number 26844, 28 SAMA; 3, 'BES
protarsi weakly expanded, second segment about 7130, TPB25/4, 26°52'50"S, 120°09'44"E, 17/5/
half length of first, third segment equal in length 99', 1 WAM, registration number 26845, 2
to first, fourth segment very small and hidden SAMA; 3, 'BES 7218, 26°51'37"S, 120°18'05"E,
within deeply lobedthird segment, apical segment 22/5/99', 2 WAM, registration numbers 26846,
long, thin, segments one to three with dense 26847, 1 SAMA; 34, 'BES 7137, SB32/1,
NIRR1DESSUSAND TJIRTUDESSUS 133
26°52'31"S 120°18'05"E\ 12 WAM, registration denser towards front. Epipleuron present in
number 26848, 15 SAMA; 3, 'BES 7136, anteriorquarter, absentin apical half.
WAM,
26°52'31"S 120°12'05"E', registration Ventral surface: Pronotal process arched in
numbers 26849, 26850, 26851; 1, 'BES 7166, lateral view, highest point (viewed ventrally)
WAM,
26°41'14"S 120°18'09"E', registration between coxae, apical halfroughly parallel-sided,
number26852; 2, BES 7228, 1 WAM, registration bluntly pointed, narrowing between coxae, not
number 26853, 1 SAMA. All collected by W. F. reaching metathorax. Mesocoxae in contact in
Humphreys & H. J. Hahn. midline. Metathorax with a few very small
punctures; quite sharply triangular in midline in
Additionalspecimen front; wings very narrow, subobsolete; narrowing
The following partial specimen probably to a broad point behind in midline. Metacoxal
belongs tothis species. BES 7222Hinklercalcrete lines, well separated, weakly diverging, reaching
east, 26°51'36"S, 120°18'05"E, 22/5/99, coll. W. to about halfway to mesosternum; sparsely
F. Humphreys & H. J. Hahn. WAM registration punctate; adpressed to first abdominal ventrite.
number 26854. Metacoxal plates and first and second ventrites
fused but sutures evident, other ventrites free,
Description (numberexamined, 106)Figs 3, 13, sternites three and four with central group of
14, 27, 35. setae, otherwise virtually without setae; virtually
Habitus: Length 1.4—1.8 mm.; relatively flat, impunctate.
elongate, pronotum narrowing at base; uniformly Legs: Protibia relatively thin, about four times
very light testaceous; hindwing vestigial, reduced as broad at apex than at base; protarsi weakly
to aboutonehalflengthofelytron. expanded, second segment about a quarter the
Head: Broad, parallel sided in basal half, length of first, fourth segment very small, hidden
rapidly narrowing forward of area where eye within deeply bilobed third segment, adhesive
would be; a short dark suture at each side in setae sparse, weak; claws weak. Mesotrochanter
middle at edge; reticulation moderate; punctures relatively large, rounded with afew setae on inner
sparse, weak, row ofsetiferous punctures running edge; mesofemur with three to four strong spines
backwards from above antennal base. Antenna on hind edge restricted to basal half but not all
moderately stout (Fig. 3), basal segment parallel grouped near base (Fig. 13); mesotarsi less
sided, second segment rounded, third much strongly expanded than protarsi. Metatrochanter
narrower than second, fourth much shorter, then large, outer edge curved, inner edge straight,
approximately the same size until penultimate, weakly pointed, well separated from femuratapex
apical segment thinner and about twice as long as (Fig. 14); metafemur relatively narrow, anterior
penultimate, a few small setae near apex of each edge weakly sinuate, impunctate, without spines;
segment. Tip of last segment of maxillary palpus metatibia strongly curved, thickening apically;
very weakly bifid, a few small setae towards tip, metatarsal segments elongate, progressively
penultimate segment much shorter than apical, smaller towards apical segment which is a little
with small papilla bearing two setae near apex longerthan penultimate, combined length ofbasal
(Fig. 27). two segments approximately equal to other three;
Pronotum: A little narrowerthan elytra(Fig. 3), claws weak, outeroneslightly smallerthaninner.
broad in front, narrowing behind, strongly Male: Appendages and legs as for female.
extended forward at anterolateral angles, Median lobe of aedeagus moderately broad,
posterolateral angles acute; punctures very sparse, concave above, tip broadly rounded with small
weak, a few larger punctures towards front edge; central point; parameres moderately broad, two
moderately reticulate; basal plicae weak, straight, segmented, apical segment with pronounced
reaching about half way along pronotum; row of narrowapicalportion (Fig. 35).
long, thin setae in front half at edges and on
forward extensions. Etymology
Elytra: Not fused but tightly locked; lacking The name pertains to the Hinkler Well
inner ridges; widest in middle; punctures very Catchment in which the classic study of the
fine, very sparse, each with a small seta, a few hydrogeochemistry ofground water calcretes was
punctures with longersetae; moderately reticulate; undertaken (Mann andDeutscher 1978).
moderately covered with micropunctures at base,
nearsuture andapex; sides ofelytraquite strongly Remarks
vertical, with row of long thin setae at edge, This is a small species with a distinctive
134 C. H. S.WATTS &W. F. HUMPHREYS
aedeagus. The pointed rather than rounded inner ridges; widest in middle; punctures very
metatrochanters and acute rather than rectangular fine, sparse, each with a small seta, a few
posterolateral angles to the pronotum, will punctures with longersetae; afew micropunctures
separate itfrom the similarsizedN. lapostaae. near apex; sides of elytra quite strongly vertical;
with row of long thin setae at edge, denser
towards front. Epipleuron broad in front,
Nirridessus cueensis sp. nov. narrowing quite rapidly to level of first sternite,
then thin to apex, difficult to differentiate from
Types disc.
Holotype: m. 'BES 7040, OldCue watersupply Ventral surface: Pronotal process arched in
bores, 27°16'11"S, 117°59'23"E, 12/5/99, coll W. lateral view, highest point (viewed ventrally)
F. Humphreys & H. J. Hahn', slide mounted, between coxae, apical half broadly spatulate,
WAM, registration number26856. narrowing between coxae, not reaching
Paratypes: 6, same data as holotype, 2 SAMA, metathorax. Mesocoxae in contact in midline.
4 WAM, registration numbers 26857, 26858, Metathorax with afew very small punctures; quite
26859, 26860; 8, same data as holotype except sharply triangular in midline in front; wings very
for, 'BES 7067, 13/5/99', 4, SAMA 4, WAM, narrow, subobsolete; rounded behind. Metacoxal
registration numbers 26861, 26862, 26863, plates with weakly raised central portion;
26864; 2, same data as holotype except for 'BES metacoxal lines weak, well separated, diverging in
7038', WAM, registration numbers 26865, 26866. anterior third, reaching to about halfway to
mesosternum; sparsely punctate; adpressedto first
Description(numberexamined, 18) Figs4, 15, abdominal ventrite. Metacoxal plates and first and
16, 29, 34. second ventrites fused but sutures evident, other
Habitus: Length 2.1-2.4 mm.; relatively flat, ventrites free, ventrites three and four with central
elongate, pronotum a little narrower than elytra, group of setae, otherwise virtually without setae;
constricted at base; uniformly very light virtuallyimpunctate.
testaceous; hindwing vestigial, reduced to about Legs: Protibia about three times as broad at
one halflengthofelytron. apex than at base; protarsi moderately expanded,
Head: Broad, parallel sided in basal half, second segment half length of first, third
rapidly narrowing forward of area where eye segment deeply bilobed, a little longer than first,
would be; a short dark suture at each side in fourth segment very small and hidden within
middle at edge; reticulation very weak; punctures bilobed third segment, adhesive setae moderately
sparse, weak, row of setiferous punctures running dense; claws moderate. Mesotrochanter rounded
backwards from above antenna base. Antenna at tip with some setae on inner edge (Fig. 15);
stout, robust, basal segment cylindrical, second mesofemur with three to five strong spines on
more elongate, third smaller narrowing to base, hind edge grouped together near base (Fig.15);
then progressively widening until penultimate, mesotarsi similar to protarsi. Metatrochanter
apical segment thinner and slightly longer, a few large, outer edge rounded, inner edge straight,
small setae near apex of each segment. Last weakly separated from femur at apex (Fig.16);
segment of maxillary palpus relatively broad, tip metafemur relatively narrow, anterior edge
weakly bifid, a few small setae towards tip. weakly sinuate, impunctate, without spines;
Penultimate segment of labial palpus with strong metatibia strongly curved, thickening apically;
cone-like projection near apex bearing two setae, metatarsal segments elongate, progressively
approximately two thirds length of apical (Fig. smaller towards apical segment which is a little
29). longer than penultimate, combined length of
Pronotum: Same width or a bit narrower than basal two segments approximately equal to other
elytra, broad in front, narrowing quite markedly three; claws weak, outerone slightly smallerthan
behind, strongly extended forward at anterolateral other.
angles, posterolateral angles rectangular; Male: Appendages and legs as above. Median
punctures sparse, weak; weakly reticulate; two lobe of aedeagus moderately broad, concave
fine, basal plicae weakly impressed, straight, above, narrowing rapidly close to tip, small brush
reaching abouta halfway along pronotum; row of of setae dorsally near tip; parameres moderately
long, thin setae in front half at edges and on broad, apical segment with pronounced narrow
forward extensions. apical portion which partly overlaps basal portion
Elytra: Not fused but tightly locked, lacking (Fig. 34).
NIRRIDESSUSAND TJIRTUDESSUS 135
Etymology aedeagus differs from mostNirridessus by having
This species is namedafterthetype locality. a group ofsetae near the apex. The parameres are
unique in Nirridessus in having the apical lobe
Remarks overlapping part of the rest of the paramere and
Nirridessus cueensis seems close to /V. with strong spinesontheinneredge (Fig. 34).
lapostaae but is larger, its pro- and mesotarsi are
much broader and its metatrochanters are not as
rounded. The spines/strong setae on the hind edge Nirridessusmorgani sp. nov.
of the mesofemur are grouped together near the
base whereasinN. lapostaaethey are more spread Types
out along the basal half of the femur. The Holotype: m. 'BES 7192, Sample 2 Site 284,
<^37^\^
FIGURES 33-37. 33, Paramere, dorsal view of central lobe and lateral view of central lobe of aedeagus of
Nirridessus morgani; 34, ditto TV. cueensis; 35, ditto N. hinkleri; 36, ditto, Tjirtudessus magnificus; 37, ditto T.
hahni.
136 C. H. S. WATTS&W. F. HUMPHREYS
mineral exploration bore, 26°41'15"S, between coxae, apical half parallel sided, tip
120°21'10"E; 21/5/99, coll W. F. Humphreys & weakly and bluntly pointed, narrowing between
H. J. Hahn', in spirit, WAM, registration number coxae, not reaching metathorax. Mesocoxae in
26867. contact in midline. Metathorax with a few small
Paratypes: 6, as for holotype, 4 SAMA, 2 punctures; broadly triangular in midline in front;
WAM, registration numbers 26868, 26869; 5, wings very narrow; narrowing to blunt point
'BES 7171, Site 262, mineral exploration bore, behind. Metacoxal plate with weakly raised
Lake Way, 26°68'74"S 120o35'31"E, 19/5/99', 1 central portion; metacoxal lines well separated,
SAMA, 4 WAM, registration numbers 26870, progressively diverging, reachingto abouthalfway
26871, 26872, 26873. to mesosternum; sparsely punctate; adpressed to
firstabdominal ventrite. Metacoxal plates andfirst
Description(numberexamined, 10) Figs6, 17, and second ventrites fused but sutures evident,
18,28,33. other ventrites free, ventrites three and four with
Habitus: Length 2.1-2.2 mm; relatively flat but central group ofsetae, otherwise virtually without
deep bodied, elongate, pronotum weakly setae; virtually impunctate.
narrowingatbase; uniformly very lighttestaceous; Legs: Protibia about three times as broad at
hindwing vestigial, reduced to about one half apex than at base; protarsi weakly expanded,
length ofelytron. second segment not much shorter than first, the
Head: Relatively narrow, parallel sided inbasal fourth segment very small and hidden within
half, rapidly narrowing forward ofarea where eye deeply bilobed third segment, adhesive setae
would be; a short dark suture at each side in sparse; claws weak. Mesotrochanter sharply
middle at edge; very weak reticulation; punctures pointed, without setae on inner edge; mesofemur
sparse, weak, row ofsetiferous punctures running with two strong setae on hind margin atbase (Fig.
backwards from above antenna base; weakly 17); mesotarsi slightly less strongly expandedthan
reticulate. Antenna relatively stout, basal two protarsi. Metatrochanter large, completely
segments broad, third narrower, fourth similar to exposed, pointed, closeto metafemurat apex (Fig.
third, then approximately equal in size until 18); metafemur relatively narrow, anterior edge
penultimate, apical segment a bit longer but same weakly sinuate, impunctate, without spines;
width, a few small setae near apex of each metatibia curved, thickening apically; metatarsal
segment. Tip of last segment of maxillary palpus segments elongate, progressively smaller towards
weakly bifid, a few small setae towards tip. apical segment which is a little longer than
Penultimate segment of labial palpus shorter than penultimate, combined length of basal two
apical, with two setae on slight bulge near apex segments approximately equal to other three;
(Fig. 28). claws weak, outerone slightly smallerthanother.
Pronotum: Muchnarrowerthanelytra, narrower Male: Appendages and legs as for female.
behind, strongly extended forward at anterolateral Median lobe of aedeagus moderately broad,
angles, posterolateral angles square; punctures concave above, narrowing to tip, without setae;
very sparse weak, a few larger punctures towards parameres moderately broad, apical segment
front edge; two strongly raised basal plicae, relatively long with small apical lobe (Fig. 33).
straight, reaching abouthalfway along pronotum;
row of long, thin setae in front half at edges and Etymology
on forwardextensions. This species is named after Kevin Morgan for
Elytra: Fused but may open slightly in his understanding of the hydrology and
preparations, lacking inner ridges; sides geochemistry of the palaeodrainage channels in
subparallel in middle; punctures very fine, sparse, WesternAustralia(Morgan 1993).
each with a small seta, a few punctures with
longer setae; moderately covered with Remarks
micropunctures particularly at base, near suture The well marked pronotal plicae and pointed
and apex; sides of elytra quite strongly vertical; metatrochanters suggest a relationship with N.
with row of long thin setae at edge, denser pulpa. The lack of an eye remnant and thinner
towards front. Epipleuron broad in front quarter, antennae will separate it from this species. The
narrowingquite rapidly to middle, absentin apical distinctive, small, apical lobe on the paramere and
half. the group ofstrong spines on the hind edge ofthe
Ventral surface: Pronotal process arched in mesofemur reduced to two will separate it from
lateral view, highest point (viewed ventrally) allotherNirridessus.