Description of the larva of Macrothemis meurgeyi Daigle from the Lesser Antilles (Anisoptera: Libellulidae)

2009·0.7 MB·English

by  Meurgey, F

Odonatologica38(4):365-368 December I,2009
Description of the larva of
Macrothemismeurgeyi Daigle
fromtheLesser Antilles
(Anisoptera: Libellulidae)
F.Meurgey
Museumd’Histoire Naturelle,12rueVoltaire,F-44000 Nantes,France
[email protected]
ReceivedMarch 19,2009/ReviewedandAcceptedJuly5,2009
Thelast instar larva isdescribed and illustrated forthefirsttime,and compared
withtheknowncongenericlarvaefromtheCaribbean. Itspeculiaritiesare:sizereduc-
tionofdorsalhooks,thepresence ofadorsalhookonsegment 2, andtheabsenceof
dorsalhooksonsegments6-9.M.meurgeyihasatriangularligulawith 10premental
setaeand 6palpalsetae.Notes ontheecologyofthisloticsp.areprovided.
INTRODUCTION
SinceMacrothemispumilaKarschwasrecentlymovedtothegenusGynothemis
(GARRISON et al.,2006) the genusMacrothemiscurrently comprises 40 spe-
cies(cf. DAIGLE, 2007), ofwhichM. meurgeyi fromGuadeloupe occurs inthe
Lesser Antilles.Its previously unknown larvais heredescribedandillustrated.
MACROTHEMISMEURGEYI DAIGLE
Figures1-7
Materia1.- 36last instarlarvae(22reared).GUADELOUPE:Riviere Corrossol,9-VI-2007,
F.Meurgeyleg.; - Riviere Bras David,stationINRA Duclos,6-II-2006,F.Meurgeyleg.;- Etang
Madere,Capesterre,alt.638 m a.s.l.,27-III-2005,F. Maddi,leg. - Allmaterial isdepositedinthe
NaturalHistoryMuseumofNantes,France.
DESCRIPTION. — Exuviaepatternedlightbrownwithblackstreaks, body stout.
Numerousintegumental setaelong (Fig. 1).
Head.-Twice as wide as long ateye level, almost squareand moderately
366 F. Meurgey
narrowedposteriorly. Smallcompound eyespearlywhitewithdarkbandsacross
theirsurface, protruding dorsally more thanlaterally oneach side ofthe head.
Cephalic lobespoorly developed but not bulging, and covered withlong setae
withablackspotanteriorly. Antennae7-segmented, 3rdsegmentthelongest. Oc-
cipital margin nearly straight, withtworoundedblackspots oneach side.Mask
spoon-shaped, the prementum-mentumarticulationreaching posterior margin
ofmesocoxae. Prementum(Fig. 2)with 10setae,lateralmarginswithsmall,stiff
setae. Ligula very prominent, 0.34 as long as its basewith distal margin finely
serratedwithsetae.Labialpalp (Fig.3)with6 setaeplusarow oflong,robust se-
FigsI-7.Macrothemismeurgeyi:(1)generalaspect,dorsalview;—(2)labium,dorsalview;—(3)right
palpallobe,dorsal view; —(4)rightproepimeron,dorsal view; - (5a)rightlegmetacoxal process,
ventero-lateral view; —(5b)rightlegmetacoxalprocess, dorsalview; —(6)lastabdominalsegments,
dorsal view; - (7)dorsal hooks,lateralview.
Larva ofMacrothemis meurgeyi 367
tae onbasalhalfof outermargin. Movableend-hooklongandincurved, shorter
thanpalpalsetae. Distalmarginofpalpal lobewith9deepcrenations, decreasing
in depth from outermargin inward.Eachcrenationwiththree(sometimes four)
setae; one largeandtwo smaller.Innermarginofpalpal lobewith asingle row
ofstiffsetae. Palpal lobesprinkled withvariabledarkspots.
Thorax.-ProthoraxbrownishyellowwithandistinctinvertedblackVmark
inthemiddle.Lateralandposterior marginalmoststraight, onlyslightly convex.
Anterior marginof proepisternum withlong setae (Fig. 4),anteriormarginof
propleuron strongly convex. Surfaceofsynthorax lightbrownwith abroaddark
band oneach, and sprinkled withvariable darkspots. Wing case light brown,
black atbasewith asmalldarkspot distallyeach. Wingcases reaching posterior
margin of abdominalsegment 5. Legs long, the posterior pair surpassing anal
pyramid whenextended.Femoraandtibiaemarkedwithblackrings,dorsaland
external surfacecoveredwithlong, stiffsetae. Mesocoxaeandmetacoxaewitha
ventrolateralspine-shaped processdistally(Fig. 5a-b),mostvisibleindorsalview.
Abdomen.- Brown, dorsallypatternedwithblack onsegments6-9(Fig. 1).
Dorsalspines/protuberances presentonsegments2-5, welldevelopedon2-4(Fig.
7), vestigialorabsentonremaindersegments. Dorsalhookonsegment2minute,
spiniform. Segments 3-4dorsalhook largeand slightlydirected backward. Seg-
ment 5dorsalhookthesmallest. Segment 5protuberance vestigial. Shortlateral
spines present onsegments 8and 9(Fig. 6). Segment 8 lateral spine parallel to
the margin ofthe body, segment9 lateralspine slightly more divergent. Cercus
sharply pointed, slightly shorter thantheparaproct.Epiproct andparaproct py-
ramidal, acutelypointed withparaproctminutely longer thanepiproct.
Measurements (mm). —Totallength(excludingantennae):14.8-15.0;prementum length:
4.9-5.0;prementumwidth3.52-3.65.
DISCUSSION. — The closest relative to Macrothemismeurgeyi is M. imitans
Karsch, as statedby DAIGLE(2007)whichoccurs only onTrinidadintheCarib-
bean.Unfortunately, thelarvaeofM.imitansisstill undescribed.Onlytwoother
Macrothemisspecies occur intheCaribbean.M. celenoisknown fromCuba, Ja-
maica, Haiti, the DominicanRepublic, andPuertoRicoin theGreaterAntilles.
M. pseudimitans isknown only fromTrinidad.Neither species occur onGuad-
eloupe whereonly M. meurgeyihasbeenfound.M. meurgeyilarvaecanbesepa-
ratedfrombothof thesespecies by thepresenceofa dorsalhookonsegment2
andtheabsenceof dorsalhooksonsegments6-9.Overall, thesizeofthe dorsal
hooksinM.meurgeyiismuchreducedwhencompared tothedorsalhooksofM.
celenoand M.pseudimitans (NEEDHAM etal, 2000). M. meurgeyi has 10pre-
mentalsetae,butM. celenoandM.pseudimitans haveonly 8-9premental setae. It
also differsfromlarvae ofM.pseudimitans by thepresenceof awelldeveloped,
spine-like metacoxalprocess (Figs 5a-b) whichisabsentin M.pseudimitans.
ECOLOGICALNOTES. — In Guadeloupe, M.meurgeyiispresentonlyon Basse-
-Terre,whereit isamontane forestspecies. Adultscanbefoundbetweensix and
368 F. Meurgey
750meters high onthe leewardcoastandbetween200and 1000meters highon
the windward coast. Mating takes place along forestmargins. Unattendedfe-
males lay theireggsby tapping thewater surfaceseveral timesin rocky streams
andrivers.Emergence takes placeearlyinthemorningonrocks, usuallybetween
thewater surfaceandupto 15centimetershigh.
Calmareas withgravelandrocks coveredwithmudoralgae are thepreferred
habitat,andlarvaecanbe seenthroughthewater surface, sprawlingon rocksor
gravel inshallowwater. Shrimps(Macrobrachiumsp.)andwater snails(Melania
tuberculata)usually occur in this habitatalso. It is interesting to note that lar-
vae of Brechmorhoga archboldi(Donnelly) werealso collectedin fasterflowing
sections of the same rivers, aboveand below theslowerareas of Macrothemis
meurgeyi habitat.Thiscouldmeanthatthereis nocompetition betweenthetwo
species in thesamerivers.
Atthe Bras-Davidriver, thewater was colouredby ferroussedimentsandthe
bottomof thebasinwas coveredwithalayer offerroussilt.Exuviaewere found
on the rocks, or ontheabrupt banks. Allthe exuviaewere coveredwith athick
depositof ferrousmud, whichfurtherindicatesthatthisspecies livesinthe bot-
tomsubstrate.
L’Etang Madere is annon-permanentcold mountainlake on Basse-Terre.
Larvae andexuviaewere foundinanentering spring thatperiodically ceases to
flow during the dry season. Exuviaewere coveredwithmud whichwould indi-
cate again thatlarvaeare bottomsubstratedwellers.Companion species atthese
sites were Argia concinnaRambur, Protoneuraromanae Meurgey, andDythemis
sterilisHagen.
ACKNOWLEDGEMENTS
1thankJERRELLJ.DAIGLEforcommentsandDENNISR.PAULSON forreviewingtheman-
uscript. Iwishtothank theNatural History Museum ofNantes andtheParc National delaGuad-
eloupeforsupportingthisstudy.
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