Descriptions of the last instar larvae of Neodythemis hildebrandti Karsch and N. afra (Ris) with comments on the status of the genus and subfamily (Anisoptera: Libellulidae, Tetrathemistinae)

2006·1.9 MB·English

by  Butler, S G

Odonatologica35(3):233-241 September 1,2006
Descriptionsof the last instar larvae
of NeodythemishildebrandtiKarsch
andN. afra (Ris) with commentsonthestatus
of thegenusandsubfamily
(Anisoptera: Libellulidae, Tetrathemistinae)
S.G.Butle¹r,D.G.Chelmick²andG.S. Vick³
1Red Willow,AllStretton,ShropshireSY66HN, United Kingdom
[email protected]
231HighBeechLane,HaywardsHeath,WestSussex, RH16 1SQ,UnitedKingdom
[email protected]
3Crossfields,LittleLondon,Tadley,Hants,RG26 5ET,United Kingdom
[email protected]
ReceivedFebruary16,2006/Reviewed andAcceptedMarch 1,2006
Thelarvae ofN. hildebrandti (fromNosy Be,Madagascar)and N.afra (fromMt
Kupe,Cameroon)aredescribed,illustratedfromexuviae,andcomparedwiththelarva
ofN. (Allorrhizucha)klingi(Karsch) fromWAfrica.Differences between the larva
ofNeodythemisand thatofotherknownAfrican Tetrathemistinae genera(Malgas-
sophlebia,Notiothemis and Tetrathemis)arehighlighted,and itis suggestedthat this
provides support forthe view that Neodythemis(includingAllorrhizucha)and Mi-
cromacromia formanatural group, the ‘neodythemistines’,and that theyareonly
distantlyrelated toothergenera in thesubfamily. Thisprovides additional evidence
forthe view thatTetrathemistinae isnota phylogeneticallyhomogenousgrouping
withinthe Libellulidae.
INTRODUCTION
Neodythemis is an African genus which is conventionally placed withinthe
Tetrathemistinaeandconsideredto containeight species, fourofwhich are en-
demicto Madagascar and fourare endemicto theAfrican mainland(DAVIES
&TOBIN, 1986).Inarecentcontribution,DIJKSTRA& VICK(2006). pointed
out thattheTetrathemistinaeas traditionally definedare a polyphyletic group-
ing andtheyidentifiedthe‘neodythemistines’, aprobably monophyletic groupof
genera,andshowedthatallthespecies describedshouldbeplaced intwogenera.
234 S.G.Butler,D.G.Chelmick&G.S.Vick
Neodythemis and Micromacromia. Using this definition, Neodythemis contains
12species, of whichfourare Malagasy endemics.
MATERIALANDMETHODS
On 13April 1999,duringasix-daystay onNosy Be (= NoseyBey), anisland offthe north-west
coastofMadagascar,thelarva ofasmalllibellulid wasfoundintheAndranobe river.Theriveritself
was fairlyswift flowingthroughlowland forest and lightlyshaded bytreecanopy.Where thewaters
had beentrappedbylargeboulders therewereslowerflowingmarginalareasandmanyoftheboul-
derswerecoveredwiththeexuviae ofZygonyxhova (Martin,1900).The larva ofN. hildebrandtiwas
dredgedfromamongstdetritusin sandysubstrate insuch anarea.Exuviae werefound clingingto
thelargerboulders inthestreamalongsideexuviae ofZ.hova. Larvae ofotherspecies foundherein-
cludedPlalycnemismalgassicaSchmidt, 1951,Pseudagrionsp.,Paragomphussp.,Orthetrum sp., and
Trithemis sp.TheNeodythemislarva wasbroughtback tothe UKand itemergedon17June 1999.
Theadult wasexamined and determinedbyG.S.Vick and R.G.Kemp,Sevensimilar exuviae which
had beenfoundclingingtoboulders inthesamehabitatwerelatercomparedwith theexuviaeofthis
larva andwereassumedtobe nonspecific.
MORPHOLOGICAL DESCRIPTIONS
NEODYTHEMISHILDEBRANDTI KARSCH, 1889
Figures 1,3,5,7
Material. - 19finalinstarexuviae,MADAGASCAR:Andranobe River,Nosy Be(13°20.33'S,
48°18.23'E), 13-IV-1999. S.G.Butlerleg.EmergedUK 17-VI-1999.
HABITUS(Fig. 1). - Totallength 17mm,similar inappearancetoPalpopleura
spp.,butratherlargerandhairierandwithstouter legs. Thereare few markings
and thebody colourismidtan.
Head. — Sub-pentagonal in shape, the lateralmargins of the occiput are
somewhatroundedwithacovering ofbothlong andshortsetae,whichare dis-
tributedfromthere to the centralsuture. Theheadis lightlymarkedon the oc-
ciput witharow ofslightly pitted, invertedU-shaped patterns.
Thelabium(Fig. 3) is cup-shaped, the distal marginof the prementumbeing
smoothwithoutamedianlobeandthere are24(left)and23(right)setae onthe
distalmargin itself.
Thementalsetae (Fig. 5)aresmalltominuteandthereare 17(left)and19(right),
arrangedinanunusualpattern. Startingfromtheoutersetathelineofsetae arches
uptowards thedistallobe thengradually returns to thesame levelat theinner-
mostseta,producing analmostsymmetricalshape (anticlinal). Thisisincontrast
to the normallineofsetae inLibellulidaewhichusuallycurves basally fromthe
outeredge andthencurvesbackdistallyattheinnermostportion(synclinal) and
also consistsof a groupof outermost long setae declining in size inwardly. The
labialpalps also showan unusualarrangement(Fig.3) asthey have2 large setae
confinedto thedistalthirdofthe palp,basal to these isa lineof smallersetae 5
Neodylhemislarvaeand statusofthegenus andTetrathemistinae 235
on right, 7 on left, these
latterare distributedal-
mostontheouteredgeof
thepalp,thusproducing a
clearlydiscontinuousline.
Thedistalmarginof the
palps has shallowcrenu-
lationseach containing
3 setae, the basal is the
longest of the threeand
the distal the shortest.
Theendhookis longand
fine, and about 1/4 the
length ofthepalps.
The antennae (Fig. 6)
are 7 segmented, the ra-
tios of length are as fol-
lows: seg. 1 = 0,5; seg. 2
= 0,6; seg. 3 =0,9; seg. 4
= 0,5; seg. 5 = 0,6; seg.
6 = 0,8 andseg. 7 = 1,0.
Thesurfaces are covered
in fine setae, which are Fig. I. N. hildebrandtiMadagascar:habitus,dorsal view.
morenoticeableonthebasalsegments.
Theeyes are small,not reaching halfway back to theoccipital marginandthe
rear marginofthe eye is angled towardsthebaso-lateralangleofthehead.
Thorax. — Theprothorax is sub-oval inshape, the outer margins bearing
a small clump of setae; overallthe thorax is slightly darkerin colourthan the
rest ofthe body. Thewing cases are dividedandreach backwards to the distal
marginofseg.4.
Thelegs havefemorawhichare stoutwithscatteredsetaedorsally andlonger,
finer setae ventrally. Thefore and middletibiaehavelonger setae dorsally and
also amixtureofstoutandfinersetae. Ventrallytheshorttibialsetaearearranged
in a central row, which extends to the tarsal comb, withlonger setae scattered
amongstthem.Therear tibiae(Fig. 7)havea distalrow oflong finesetae,plus
severalwhichare stouter.Theventralsurfacehas finersetae, whichgraduate to
6 stoutandcurvedsetae,with2 moreon theedge ofthearticulation.
Abdomen (Fig. 1). - Itis lightbrownincolourandhas no visiblemark-
ings.Fineshortsetaeare noticeableon segs 8-10, butare sparser onthepreced-
ing segments. Long, fine setae are also present on the latero-distalmargins of
segs 5-9andalso onthecentreofthedorsumatsegs 4-8, they arealso scattered
irregularly over therest ofthedorsalsurface.Alsothere is a row of short, fine
236 S.G.Butler,D.G.Chelmick&G.S.Vick
setae onthe distalmarginof segs 5-9. No dorsal orlateralspines are visible on
any segment.Spines arepresent ventrallyon the distalmarginsofsegs 7,8and
9. Triangularsclerites are detectableonsegs 3-5andfaintly onseg. 6.
The anal appendages are of the same pale colour, except at the tips, which
are darkened.Theepiproct isapproximately the samelength as seg. 9,the cerci
reaching to V* ofits length, whilst theparaprocts are approximately the length
ofsegs 9+10combined.
Comparative material. -6finalinstarexuviaefromAndranobe R,Nosy Beand 1from
Moramanga,nearAntananarivo incentral Madagascar,25-IV-99. M.J.Parrleg.
All the above exuviae foundin situ at Nosy Be and Moramanga are slightly
smaller, ranging in size from 13-14,5 mm.They are muchdarkerincolourand
appearslightly hairierandcoveredinagreateramount ofdetritus,though those
differencescouldbeaccentuatedby thecleanerartificial environmentinwhichthe
bredspecimen wasreared.Thereisa definitecentrallobeontheligula. Thesetae
onthe prementumappearsmallerandfewerin number, howeverthisis difficult
to discern exactly, as theempty labiumofeach had filledwith grains of sand,
whichare impossible toremove. As thesedifferencesare not significant enough
to point to a differentspecies, cohabiting at the samesite, thismaterialis tobe
assumedtobe nonspecific with thedescribedlarva.
Ofthe fourMadagascan species, N. hildebrandtiis thecommonest species, re-
cordedfrommost partsofthe island, including Antananarivo, which isnearto
Moramanga. N.arnoultiFraser, 1955hasonlybeenrecordedfromeastern Mada-
gascar(Mt Andohelo1800m, 1 tJ),N. trinervulata(Martin, 1903) fromeastern
Madagascar (Col de Sakavalona, 1 6),whereas N. pauliana Fraser, 1952is re-
cordedonly fromcentral Madagascar (Foret auNordd’Anisobe, 1 6).Thesta-
tusoftheselastthreespecies needs tobe confirmed.
NEODYTHEMISAFRA(RIS, 1909)
Figures2,4
Material. — 3exuviae offinalinstarlarvae,MountKupe,SWCameroon(4°49.15'N,9°41,48'E):
1d takenwithadult (preserveddryandpinned,taken IV-1997),1 9 foundalone(preservedin 70%
alcohol,taken 11-1996)andinclose agreementwithfirst,OttoMesumbe leg.,1 ibred outby D.G,
Chelmick 1998;all G.S.Vickdet.All specimensareclean andnotencrusted with mud.
ThelarvaeresemblethoseofNeodythemis hildebrandti.Somedifferencesareof
coursetobeexpected andwepoint outthefollowing asbeing diagnosticofafra.
Thesetae onthelateralandhindmargins ofthe headare longer (reaching0.8
mm)andthe rear angles ofthehead are more nearly square(Fig. 2).On thela-
bium(Fig.4) thereisasuggestion ofamedianlobeandthereare 14-15setaeper
sideonthedistalmargin(ratherthan23-24); theextraordinary ‘reverse-curve’of
prementalsetae onthedorsalsurfaceisifanything moreprominentaseachcurve
Neodythemislarvaeandstatusofthegenusand Tetrathemistinae 237
ofsetae hasasmaller
radius and there are
fewersetae(13-14per
side rather than 17-
19). The distal mar-
ginsofthelabialpalps
bearten crenulations
butonly thebasalsix
beartriple setae. The
frons bears longer
hairs, exceeding 1.0
mm,andthey areno-
ticeably yellow. The
antennae are also 7-
segmentedbutthera-
tios of lengths are as
follows: seg. 1 = 0.5;
seg. 2 =0.6; seg. 3 =
1.2;seg.4=0.7; seg.5
= 0.8; seg.6 =0.8and
seg. 7 = 1.0(note the
greaterrelativelength
of seg. 3 in afra). In
both species, the ab-
domen bears very
long finesetae onthe
dorsum, arising near
the distal margin of
segments4to8(a few
Fig.2. N.afraCameroon: habitus,dorsal view. also onseg. 3inafro)
andtheseextendover
theintersegmental membraneonto thenextsegment,butthey are slightlylonger
inafraandthe disposition is differentas they are moreevenly distributedacross
thedorsum inafra, and not most concentratedon the mid-line(cf.Figs 1, 2).
Finallythecaudalpyramid is moreprominent inafra; theepipoct is longer and
aboutequal to seg.9+10, the paraprocts are slightly longer than theepiproct,
andthecerci areabout0.6of length ofepiproct.
DISCUSSION
Thereis atpresentno classificationofthe Libellulidaewhichreflects modem
concepts ofphylogeny. Traditionalclassificationsare mainlybased upon wing
238 S.G.Butler,D.G.Chelmick&G.S.Vick
venationandthese are unreliableandlikely to leadto falsephylogenies (DIJK-
STRA& VICK,2006). TheTetrathemistinaeispoorlydefinedas itisbasedsolely
uponadultcharacterswhichmaybeplesiomorphic,anditisprobably polyphyletic
(VICK, 2000). They havegenerally beenconsideredto bea‘primitive’ groupof
libellulids,allare smallformswithlongnarrow wings, shortabdomen, coloured
blackandyellowanddisplaying anumberofpossibly plesiomorphic wingvena-
tionalfeatures. Itis possible, however, thatsome ofthesecharacters are infact
secondary developments which are correlatedwith a narrowing of the wings.
They display a numberof specialised characteristics: superior appendages are
frequently complex inshape (and hence are useful diagnostically at the species
level),unlikethosepossessed bymostof themore‘modern’libellulidsandthey
possessarangeofinterestingoviposition strategies. Mostspecies inhabitclosed-
-canopyhabitatsinrainforests, some generaare predominantly stream dwellers,
whilstothersbreedinshadypools.
DIJKSTRA & VICK(2006) discussed the status of a group of apparently
monophyletic taxa,previously consideredtobemembersoftheTetrathemistinae,
whichthey haveforconvenience, pending arevisionofthefamily,calledthe‘nee-
dythemistinae’.Allspeciespossess two well-definedcharacters:similarhamular
structuresandadditionalbridge cross-veins; also there isatendency to develop
double-rowedforewing discoidalcellsandadditionalcross-veins inthecubitaland
discoidalcells.They arranged the species in two generaNeodythemis (including
AllorrhizuchaKarsch, 1890andMesumbethemisVick,2000) andMicromacromia
Figs3-7. Nhildebrandti (Figs3,5-7) andN. afra(Fig.4):(3-4)labium,dorsalview,showingsetal ar-
rangementonpalpsandmental setae; —(5)preraentumincloseup,showingdetailofmentalsetae;
- (6)right antenna,dorsal view; - (7)righthind leg,dorsal view.
Neodylhemislarvae andstatusofthegenusandTetrathemistinae 239
(including EothemisRis, 1909,andMonardithemisLongfield, 1947).Othergenera
placed intheTetrathemistinaewere consideredtobeonly distantlyrelatedtothe
‘neodythemistines’ andarenot necessarily monophyletic themselves.
Littleappears tobeknownofthe larvaeofmany ofthe species oftheTetra-
themistinae, but descriptions are available of the larvae of certain African
generawhich are all ‘non-neodythemistine’. The larvae of Tetrathemis long-
fieldae Legrand, 1977is known (LEGRAND, 1977) and materialof T. bifida
Fraser, 1941 isavailable(CHELMICK, 2000). Thetwo species of Notiothemis
have beendescribed:jonesi Ris, 1919(SAMWAYS et al.,1997)androbertsiFra-
ser, 1944(CLAUSNITZER, 1999). Also the larvae of the Asian Tetrathemis
irregularis Brauer, 1868 (NEEDHAM & GYGER, 1937), T. platyptera Selys,
1878(VAN TOE, 1992)and Nannophlebia risi Tillyard, 1913(HAWKING &
THEISCHINGER, 1999) have beendescribed.Allof the generaaboveappear
to havelarvaewhichshare a numberof characters:they have dorsalspines, or
definite dorsalridges relating to dorsal spines, long legs and a somewhatSym-
petrum-like appearance(particularly regarding theshapeofthehead).Inallthese
generathelabiumpossesses large crenulationsonthedistalmarginofthelabial
palpus. AnotherAfricangenusMalgassophlebia, haslarvaesimilarto theabove,
exceptthattheseare notlong-legged andbothM. aequatoris Legrand, 1979and
M. westfalliLegrand, 1986have lateralspines on segments 7-9and 6-9 respec-
tively,whereasthe othershaveeithernoneorthey are smallandconfinedto segs
8&9(LEGRAND, 1986).
Wepossess larvalmaterialofthreeofthespecies of Neodythemis:N. afra(Figs
2,4)andN. klingi(Karsch, 1890)fromSouth-WestCameroon(unpublished) and
N. hildebrandti(this paper). Thefirst taxon is thecorrect name forN. africana
Fraser, 1954andthesecond taxon wasoriginally placed inAllorrhizucha, which
isnowsynonymised withNeodythemis (DIJKSTRA & VICK, 2006).Thereap-
peartobesignificant differencesbetweenthesethreeNeodythemis species onthe
one handandthe otherdescribedmembersof the ‘Tetrathemistinae’(as listed
above)ontheother. Firstly, theNeodythemis head(Figs 1,2)bears a closesimi-
larityto thatof Orthetrumspp., havingsmalleyes andasubparallel lateralmar-
gin behind the eye, in contrast to the angled and convergentSympetrum-type
head withlargereyes ofthe abovementionedgenera.Secondly thelabiumhas
thevery characteristic‘reverse-curve’ofsetae ontheprementum(Figs 3,4)and
the labialpalps withvery shallowcrenulationson thedistal margins ofthe la-
bialpalps andas fewas 2+ 1 spines. Thirdly, theabdomenisparticularlyhairy,
somuchsothatall exuviaeof N. hildebrandtihadtobe cleanedofclinging mud
thoroughly beforethey couldbe properly examined; whereasthe other genera
appearto havesmoothlarvae.Fourthly, the legsare slightly stouter andarecer-
tainly shorterthanthosein theothergeneradescribed; ifextendedthehindlegs
wouldonlyjust clearthedistalmargin oftheabdomen.
Itisinterestingthatthelarvaeofthethreespecies aresosimilarasthey arevery
240 S.G.Butler,D.G.Chelmick &G.S,Vick
widely separated ontheAfricancontinent, N. afraandN.klingifromthetropical
AfricanmainlandandN.hildebrandtiendemictoMadagascar. Theselarvalchar-
actersthereforesupporttheircommon generic status andsuggest strongly that
Neodythemis is awelldefinedgenus.Wehavenotseen thelarvaofMicromacro-
mia, butwehavebeeninformedthat the larvaof M. camerunicaKarsch, 1890
is similarand though ‘ratherclose’ to that of Neodythemis with regard to head
shapeandanticlinal(inverted) patternofmentalsetae,neverthelessbearsdistinct
differences, not least inthe presenceof dorsal spines ofthe abdomenand lack
of long setae on the posterior marginof the abdominaltergites (Dr G. Fleck,
pers. comm.).
Thetwo genera Neodythemis and Micromacromiaare clearly closely related
toeachotherandprobably formanaturalgroup;they are only distantlyrelated
to othergenerapresentlyclassified withinthe subfamily. Thissupports the view
thatthe Tetrathemistinae, likeseveral otherlibellulidsubfamiliesare notaphy-
logenetically homogenous group.
ACKNOWLEDGEMENTS
Weshouldlike tothank GUNTHER FLECK forvaluable informationconcerningrelated spe-
ciesoflarvae,K.-D.B.DIJKSTRA, R.G.KEMPand F.SUHL1NG forhelpfuldiscussionsontax-
onomy;and thelateD.A.L. DAVIES,thelateE.V.PRENDERGASTand M.J.PARRfor assistance
in thefieldin Madagascar.
REFERENCES
CHELMICK, D.G., 2000. ThedragonfliesofcentralAfrica.An identificationkeytothelarvae.The
Cameroon Dragonfly Project. Privatepublicationavailable fromthe author.
CLAUSNITZER,V.,1999. Descriptionofthefinal instarlarvaofNotiothemisrobertsi Fraser 1944.
(Anisoptera;Libellulidae).Ini. J. Odonatol. 2(1): 77-82.
DAVIES,D.A.L.&P.TOBIN, 1985. The dragonfliesoftheworld: asystematiclistofthe extantOdo-
nata,vol. 2.Anisoptera.Soc.Int.Odonatol.,Utrecht.
DIJKSTRA, K-D.B.&G.S.VICK, 2006. Inflationby venation and thebankruptcy oftraditional
genera:thecaseofNeodythemisand Micromacromia,withkeys tothe continental African
species and thedescriptionoftwonewNeodythemisspecies from theAlbertine Rift(Odo-
nata:Libellulidae).Int. J. Odonatol. 9(1): 51-70.
FRASER, EC, 1956.Faune deMadagascar. 1.Insectesodonatesanisopteres. 125pp. Inst.Rech. scl-
ent.,Tananarive.
LEGRAND,J„ 1977. DeuxTetrathemisBrauernouveauxduGabonetlalarvede1’un de1’eux(Ani-
soptera,Libellulidae).Odonatologica6(4): 245-251.
LEGRAND,J., 1986. Malgassophlebiawestfalli spec,nov.,nouveauTetratheminae Afrotropicaldes
forets deGabon oriental: Images, larves,notesbiologiqueset discussion surle genre(Ani-
soptera:Libellulidae).Odonatologica 15(1):97-105.
NEEDHAM, J.G.&M.K.GEYGER, 1937.The OdonataofthePhilippines.Philipp. J.Sci. 63(1):
21-101,pis 1-10excl.
SAMWAYS, M.J.,G,WHITELEY,M.DI DOMENICO&G.CARCHINI, 1997.Description of
the last instar larva of Notiothemis jonesiRis, 1919 (Anisoptera;Libellulidae).Odonato-
Neodythemislarvaeandstatus ofthegenusand Tetrathemistinae 241
logica26(2):221-226.
HAWKING,J.H.&G.THEISCHINGER, 1999.Dragonflylarvae (Odonata).Aguidetotheiden-
tificationoflarvaeofAustralianfamiliesandtothe identificationandecologyoflarvaefrom
NewSouth Wales. Coop.Res.Cent.Freshw. Ecol.Thurgoona(NSW)&Austr.WaterTech-
nologiesPty.,WestRyde (NSW).
VAN TOL, J„ 1992. An annotatedindexto namesofOdonata used inpublicationsbyM.A. Lief-
tinck.Zool. Verb. Leiden 279: 1-263.
VICK,G.S., 2000. Mesumbethemis takamandensis gen. nov., spec,nov., anewgenus and species
oftheTetrathemistinae fromCameroon,with akeyto theAfrican generaofthesubfamily
(Anisoptera:Libellulidae).Odonatologica29(3):225-227.