Odonatologica26(1): 75-81 March I. 1997 Descriptionandnaturalhistory oftheCosta Rican Odonatalarvae.5. Megaloprepuscaerulatus(Drury, 1782) (Zygoptera, Pseudostigmatidae) A.Ramírez InstituteofEcology, University ofGeorgia,Athens,GA 30602,United States Received May8, 1996 /ReviewedandAcceptedAugust20, 1996 The larva is described and illustrated, and a comparisonis madewith the other described spp. in the family. The most useful characteristic forthe separation ofthe different spp. isthe shape ofthepalespotonthe tipofeach caudal gill.Adiscussion ofthe morphologicalsimilarities ofthe phytotelmatadwellersispresented and it is notedthat spp. ofZygopteraaremore similartooneanotherand share morespecial- izedcharacteristics thantheAnisopteraspp. Also,the larvae ofthe Pseudostigmatidae are very similartothose ofCoenagrionidaethat breed inphytotelmata,the main dif- ferences beingbody size andnumber and shapeoflabial palpiteeth. INTRODUCTION The family Pseudostigmatidae has been a subject of research since early odonatologists foundadults flying inthe forest farfrom any typical or obvious larvalhabitat.Whilereseachers wereabletocollectandstudytheadults, thelarval habitatremainedunknownformanyyears. DrD.C. Geijskes wasoneofthefirstto try to find the microhabitatof the larvae, particularly that of Megaloprepus caerulatus.Themostlikely habitatatthattimewas thoughttobetank bromeliads (CALVERT, 1923),and itwas not untilthe 1985S.I.O. Symposium inParis, that GeijskeslearnedfromO.M.Fincke thatthelarvaeare tree holedwellers.Itwas his wishto describethelarvaebuthis untimely deathmadethis impossible. I, there- fore,dedicatethismodestpapertothememoryof DrD.C. G eijs k es, though it cannot becompared withwhathewould havedone. Severalinteresting papershavebeenpublished on theecology and taxonomyof the family Pseudostigmatidae (CALVERT, 1911, 1923;FINCKE, 1984, 1992). However, the larval taxonomy developed slowly, mainly because the specific 76 A.Ramirez microhabitatmakesthecollectionofspecimens difficult. The family has six species in Central America, split among three genera (PAULSON, 1982). Thereare four knownspecies; Mecistogaster modesta (Sel.) (CALVERT, 1911),M. ornata Ramb.(RAMIREZ, 1995),Pseudostigma aberrans Sel. (NOVELO-GUTIERREZ, 1993) and Megaloprepus caerulatus (Dru.). NOVELO-GUTIERREZ (1993) statedthatthelarvae ofatleasttwo more species havebeenreared forecological studies, butformaldescription arestill tobe com- pleted. Previousto the present study, Megaloprepus caerulatuslarvae were separated fromotherspecies usingcharactersprovided by earlierecological studies(FINCKE, 1984, 1992;DELA ROSA & RAMIREZ, 1995). Forexample, FINCKE (1992) briefly described how to separate several species ofthe family, amongthem M. caerulatus. Thelarvaeusedforthepresentstudy werefoundliving insmallwater bodiesin tree holes.Almostallofthetree holeshadacapacity ofnearly oneliterand were situatedatdifferentheights above theforest floor. Also foundwith the larvae were larvae of M. ornata, (Pseudostigmatidae), Orthemisferruginea (Fab.) (Libellulidae)aswellaschironomidsandotherdipterans. MEGALOPREPUSCAERULATUS (DRURY, 1782) Figures 1-6 Material. - 2exuviae (6,9) ofspecimensemergedin laboratory,2 larvae(<J, 9), lastinstar, 2intermediate instars, Maritza Biological Station,Guanacaste Conservation Area,Guanacaste prov- ince,24-1-1994, A.Ramirez,N.Barbee&C. delaRosa, leg.;- 2larvae (3, 9), lastinstar,collected in 1986;- 3 exuviae (<J, 9), last instar, 27-XI-1982 & 2-XI1-1982. 6 larvae, (<5, 9), intermediate instars, 11-1986. Barro Colorado BiologicalStation,Panama, O.M.Fincke leg. DESCRIPTION. - Larvaeand exuviaelight brown or brown; body slender and long, almostentirely glabrous, withseveral distinctivepale areas, asfollows:three whitespots on themid-dorsalfaceofthethorax,two behindthespiracles andone inthemiddle,betweenthespiracles (Fig. 1).Oneconspicuous whitespot atthetip ofeach caudalgill. Head.-Widerthanlong,occiput smallandconcave, cephaliclobespronounced and rounded, withgroupsofspiniform setae; labrumwith two pale lines ateach sideofthemidline,slightly converging inthemiddle,indorsalview;clypeusbrown with atriangularmiddorsalpale area, justinfrontofthelineson labrum.Antennae 7-jointed, as long as thehead,glabrous or with fewscattered setaejust proximad thearticulations; uniformly colored;proportion ofantennomeres,frombase totip: 0.37, 0.51, 1.0, 0.67,0.45, 0.30, 0.15. Mandibles biramous,external branch with fourteeth, theventralone witha smalltoothatits base, internalbranchwithtwo teeth. Galeolaciniaewith four, robust andslightly curved teeth,similarin length and arranged ina row, with scattered setae throughout; maxillary palpi covered LarvaofMegaloprepuscaerulatus 77 withnumerouslong setae.Labiumlightbrown,prementum-postmentumarticula- tionreaching the proximal margin ofthe mesocoxae; prementumglabrous, but with arow of small spines on the apical 0.25 (Fig. 4); ligula prominent with the margin serrated. Palpal setae 6-7, basal 0.7ofexternal margin withsmall setae, internal margin smooth; two palpal teethofsimilar shape (Fig. 5). Thorax.-Pronotumglabrous, posterolateral angles rounded, frontalmargin bilobed, lateral margins with long setae; posterior margin with threedistinctive pale areas, onebehindeach spiracle and anotherinthe midline.Synthorax with Figs 1-6. Larval morphologyofMegaloprepuscaerulatus: (1)female, last instar, generaldorsal as- pect;- (2)femalegonapophyses,lateralview;- (3)caudalgill,lateral view;- (4)prementum, dorsal view;—(5)labialpalpi, dorsalview; - (6)female cercus,lateral view. 78 A.Ramirez some mediumsize setae on the lateral margins, a pale area along the anterior middorsal line. Hind pair of wing sheaths reaching the posterior margin of ab- dominalsegment5, thefront pairreaching the0.5ofthesamesegment.Legs light brown, femorawith 2rows of dorsal, 2 ofventral and one lateralsmall spines; tibiaewith2 ventralrowsofsmallspines andsomescattered dorsalsetae,distal0.2 with a densegroupofsmallspines, nearthearticulationwiththetarsus;tarsus 3- -jointed withtworows ofventralspinesandlongsetae onthedorsalside.Pulviliform empodium presentontarsus. Abdomen.- Uniformly lightbrown, darkernextto theposteriormargins of eachsegment,completely glabrous, butposteriormargin ofsegment10witharow of small setae; withouteitherdorsal protuberances, or lateral spines. Female gonapophyses reaching the basal 0.6 ofsegment 10, external lobes ending in a roundedtip with asmall spine, theinner onesshorter than theexternals (Fig. 2). Male gonapophyses cone shaped, ending acutely and not reaching the posterior marginofsegment9.Maleandfemalecercismallandconical(Fig.6). Caudalgills flattened(Fig. 3),slightly longer thanwide,darkbrownandharderintexture inthe basal0.25,therest graycolored with violetanda softertexture nearthe borders; witha distinctivepale area atthetip ofeachone. Measurements (inmm). - Total length (excluding gills)22, abdomen 15,lateral gills 4, medial gill4,metafemur5;- head: width 5,length3;- prementum: width 3,length5. variation. - Somespecimens hadamodifiedtarsus onthefrontor middlelegs; they were 2-jointed andoneoftheclaws was larger thantheother. DISCUSSION AllPseudostigmatidae larvaeare characterizedby being adapted to liveinvery similarandsometimesidenticalmicrohabitats.Forexample,fourofthesix species ofthe family in Central America have been found living in tree holes and it is known thatthreeor morespecies areableto livetogether inthesametree holeat thesametime(FINCKE, 1992;DELAROSA& RAMIREZ, 1995).Thissuggests thatdifferentgenerawere subjecttosimilarselectionpressures, probably resulting inthemorphological similarity observed amonglarvaeofthePseudostigmatidae. Theshape andstructureofthecaudal gillsare themostusefulcharactertosepa- rate thegenera;they arebasically leaf-like,but vary insizeandshape. Thefactthat two genera.Pseudostigma and Megaloprepus, havepale areas atthetip moreevi- dentin thelatter, makes genusidentificationeasier.Allknown species ofPseudo- stigmatidae larvaecanbeseparated using thekey in RAMIREZ(1995). THE PHYTOTELMATADWELLERS Among Odonataitis not uncommonto findspecies withlarvaethatliveintree holes,bromeliadsor similarhabitats,generally knownas phytotelmata (CORBET, Larva ofMegaloprepuscaerulalus 79 1983).Someofthesespecies areopportunistic as is thecase inseveralAnisoptera species such asOrthemisferruginea andLibellulaherculea(pers. observ.). Others, however,seem tospecialize in thiskindofhabitat, forexample all species inthe familyPseudostigmatidae andthecoenagrionid genusLeptagrion. Fromaliteraturereviewitisevidentthatanisopteran larvaelivinginphytotelmata do not show special morphological adaptations and that larvae are morphologi- callyidenticaltothosethatliveinothertypesofhabitats(e.g. pools). Severalspe- cies of Aeshnidae, such as Indaeschna grubaueri (Forster) (ORR, 1994), and Gynacantha membranalisKarsch (SANTOS et al., 1987;FINCKE, 1984), have beenfound living in phytotelmata andin pools on theground, withoutany mor- phological characteristicsthatcouldindicateanadaptationtoanyofthesehabitats, besides differentcolor patterns, whichare known to vary with the color ofthe microhabitat(CORBET, 1960;RAMIREZ, 1994). ThecaseofZygoptera larvaeiscompletely different.Larvaeofdifferentfamilies andgenerathatdwell inphytotelmata tendtobemoresimilaramong themselves, sharingmanymorphological characteristics.Theseincludemodifiedleaf-likegills (Fig. 3)usually coloredblack andpurple,glabrous bodies, darkcolorpattern,short labiumwith triangular prementum, shortlegs, and labialpalpus with 4-5 setae. Phytotelmata dwellers tend to be larger than related species that do not use this habitat(ORR, 1994).LarvaeofthefamilyPseudostigmatidae andCoenagrionidae are ingeneral verydifferent, butwhenlarvaeoftheformerarecompared with the species ofthelatterthatbreedinphytotelmata, thedifferencesarelessevident.DE MARMELS (1985)described thelarvaeof Leptagrion fernandezianum Racenis whichliveinbromeliads.Fromhis descriptions andcommentstheresemblanceof thespecies toMecistogasterisclear.ORR(1994)describedthelarvaeofPericnemis triangularis Laidlaw(Coenagrionidae). This species also shows all the morpho- logical characteristics ofthe phytotelmata dwellers(see above). Finally, another bromeliaddwellerisDiceratobasismacrogaster(Sel.) (Coenagrionidae) (WEST- FALL, 1976).Inthis case thelarvais similartotheotherspecies describedabove only differing in the shape of the caudal gills, which are more typical of Coenagrionidae. Morphologically, D.macrogasterrepresentsanintermediatestep betweenthenormalCoenagrionidae andthephytotelmata dwellers. Inconclusion,phytotelmata-dwelling species ofCoenagrionidae andallspecies ofPseudostigmatidae are morphologically similar.Thedifferencesare mainly the size andshape ofthelabialpalpi, thedisposition ofthepremental setae, andin a few cases, shape ofthe caudal gills. Pseudostigmatidae lack thepremental setae andthelabialpalpi havetwo endteeth(Fig. 5).However,thesecharacteristicsare variable among the phytotelmata-dwelling Coenagrionidae. For example, P. triangularis lacks the premental setae but itslabialpalpi are modified, with one endhook andaserrated area. Thelabialpalpi ofL.fernandezianum is similar to thoseofPseudostigmatidae butithaspremental setae.Thelength ofthefinalinstar inPseudostigmatidae is notless than 18mm, whileinCoenagrionidae itis usually 80 A.Ramirez not morethan 18 mm. SANTOS (1966) and DE MARMELS (1985) concluded that the Pseudo- stigmatidaeevolvedfrom theCoenagrionidae. This conclusionissupported by the present study. In orderto improve our understanding ofthis relationship more Coenagrionidae larvaeneed tobereared and described. ACKNOWLEDGEMENTS Iam verygratefultoDr C.DELA ROSAforhishelpcollectingthematerial, toDr P,CORBET for kindly givingmethehonor ofdescribingthelarvae, tohim and DrO.M.FINCKEforallowingmeto studytheirspecimens, and toDrP. HANSON, DrP.CorbetandJ.P. BENSTEADfortheircomments onthemanuscript. REFERENCES CALVERT, PR, 1911. StudiesonCostaRicanOdonata. 2&3.The habits, structure and transforma- tion ofthe plant-dwellinglarva ofMecistogastermodestus. Ent. News 22(9/10): 402-411, 449-460,pis 18-19 excl. CALVERT. PR, 1923.Studieson CostaRicanOdonata, 10. Megaloprepus,its distribution,variation, habits and food. Ent. News 34(5/6): 129-135, 168-174. CORBET, P.S., 1962. Thebiologyofdragonflies.Witherby, London. CORBET,PS., 1983. Odonatain phytotelmata.In: J.H. Frank &L.P.Lounibos,[Eds],Phytotelmata: terrestrialplants ashosts foraquaticinsect communities, pp. 29-54, Plexus, Medford,N.J, DE LA ROSA,C.& A.RAMIREZ, 1995. Anoteonphototacticbehavior andphoneticassociates in larvae of Mecistogaster ornata Rambur from northern Costa Rica (Pseudostigmatidae, Zygoptera). Odonatologica24(2);289-294. DE MARMELS,J., 1985, La nSyade de Leptagrionfemandezianum Rdcenis, especiebromelfcola (Odonata:Coenagrionidae),yconsideraciones sobrelaposiblerelacidn filogeneticadel genero LeptagrionSelys. Bol.Ent. venezol. (NS) 4(1): 1-7, FINCKE,O.M., 1984.Giant damselflies inatropical forest: ReproductivebiologyofMegaloprepus coerulatus with notes on Mecistogaster(Zygoptera: Pseudostigmatidae),Adv. Odonatol. 2: 13-27. FINCKE, O.M., 1992. Behavioralecologyofthe giant damselflies(Odonata: Zygoptera: Pseudo- stigmatidae)ofBarro Colorado Island,Panama. In:D.Quintero& A,Aiello,[Eds],Insectsof Panamaand Mesoamerica,pp. 102-113,OxfordUniv. Press,Oxford-NewYork-Tokyo. NOVELO-GUTIERREZ, R., 1993. La ndyadede Pseudostigma aberrans Selys, 1860 (Odonata; Zygoptera: Pseudostigmatidae).Fol. ent. mex. 87: 55-60. ORR,A.G., 1994. Lifehistories andecologyofOdonatabreedingin phytotelmatain Borneanrainfor- est. Odonatologica23(4): 365-377. PAULSON, D.R., 1982. Odonata. In'.S.H. Hurlbert&A.Villalobos-Figueroa,[Eds],Aquaticbiota of Mexico,Central America and theWestIndies, pp.249-277, San DiegoSt. Univ.,SanDiego, CA. RAMIREZ, A,, 1994. Descripci6ne historia natural delas nayadesde Odonata de Costa Rica. 2. Archilestes neblina (Rambur, 1842) (Zygoptera,Lestidae) conuna clavepara el generoen CostaRica. Fol.ent.mex. 90: 9-16. RAMfREZ, A., 1995. Descripci6n ehistoria natural de las larvas de Odonata de Costa Rica. 4. Mecistogasteromata(Rambur, 1842) (Zygoplera,Pseudostigmatidae).Bull. Am. Odonatol. 3(2):43-47. Larva ofMegaloprepuscaerulatus 81 SANTOS,N.D., 1966, Contribugaoconhecimento dafauna doEstadodaGuanabara, 56.Notas sobre coenagriideos(Odonata)quesecriam enbromelias. AlasSoc.Biol. Riode J. 10:83-85. SANTOS, N.D.,J.M. COSTA&J.R.P.LUZ, 1987. Descri9ao daninfadeGynacanthamembranalis Karsch, 1891 (Odonata: Gynacanthini)e notas sobre oimago.Anais Soc. ent. Brasil. 16(2): 437-443.