Vol. 107,No.3,May&June, 1996 137 OCCURRENCE OF ALDERFLY LARVAE (MEGALOPTERA) IN A WEST VIRGINIA POPULATION OF THE PURPLE PITCHER PLANT, SARRACENIA PURPUREA L. (SARRACENIACEAE)1 J.L. Pittman,2T.S.Turner,2 L.Frederick,2 R.L.Petersen,2 M. E. Poston,2 M. Mackenzie,3 R. M.Duffield2'4 ABSTRACT:Eightalderfly(Sialidae)larvaewereidentifiedinthecontentsof99leavescollected May 14-15, 1994, fromapopulation ofthe purple pitcherplant,Sarraceniapurpurea, from Big RunBog,TuckerCounty,WestVirginia.Fiveofthelarvaeweresurroundedbymyceliamats.The fungus belonged to the water mold genus, Sapmlegnia (Saprolegniaceae). Adult alderflies col- lectedfromthesamelocalityinJuneweredeterminedtobeSialisjoppa.Theoccurrenceofalderfly larvaeinpitcherplantsisunusual,andprobablyrelatedtofloodingofthehabitat. Alderflies(Sialidae)areasmallfamilyofaquaticinsectswithapproximately 23 North American species (Evans, 1984). The predacious aquatic larvae can be abundant in streams, rivers and ponds. Larvae migrate from the water and pupateon dry ground several yards from the water. Adult insects are generally found in the same areas as the immatures. They are usually inactive, resting in thevegetationneartheirlarvalhabitats.InWestVirginia,fourspeciesofalderflies have been reported (Tartaretal., 1973; 1978) . While studying apopulation ofpurplepitcherplants, Sarraceniapurpurea L, in West Virginia, the contents trapped at the base of several leaves were analyzed by transferring the materials into separate petri dishes. One of the leavescontained alarvaapproximately 1.0cmlong, which was lateridentified as belonging to the genus Sialis (Sialidae). Astudy was initiated to determine whethersialid larvae are common to this population ofpitcherplants. This study is significantbecause itaddstoourknowledgeofthe biology of pitcher plants. Although a variety of species of arthropods are known to be regular inhabitants ofthese unusual carnivorous plants, it is not clear whether sialid larvae areprey, occasional associates orregular inhabitants. 1 ReceivedOctober23, 1995;AcceptedNovember28, 1995. 2 DepartmentofBiology,Howard University,Washington,D.C.20059. 3UnitedStatesDepartmWenVtofAgriculture,ForestService,Forest-HealthProtection, 180Canfield Street,Morgantown, 26505. 4Towhomcorrespondenceshouldbesent. ENT.NEWS 107(3): 137-140,May&June, 1996 138 ENTOMOLOGICALNEWS METHODS TheS.purpureaWpopulation is located in BigRun Bog located at39 07'N latitudeand 79 35' longitude, TuckerCounty, WestVirginiaatanelevation of 980 m above sea level. The bog occupies approximately 20-25 ha in the MonongahelaNational Forest (Wiederetal. 1981). Big Run Bog (also known asOlsonBog)isdominatedbySphagnumandPolytrichumwhichtogethercover 85% ofthe surface (Wiederetal. 1981). Sarraceniapurpurea was introduced tothisbogin 1946(StrausbaughandCore, 1970)andiswellestablishedtoday. On May 18, 1994 fourmatureplants werecollected forleafanalysis. Indi- vidual plants were scooped up by hand,placed inplasticpans with water, cov- eredandtransportedbacktothelaboratoryatBlackwaterFallsStatePark.Three additional plants werecollectedJune 14-15, 1994. During thetwo visits to the bog in 1994, adultinsects werecollected using bothasweepnetandabeatingsheet.Inearlyspringofthenextyear(March30, 1995), aquatic specimens were collected using an aquatic insect net from the shallow waterin the same vicinity where thepitcherplants had been collected previously. Specimens werepreserved in 70% ethanol. Individualleaveswereanalyzedafterremovalfromthemainclusterbycut- tingthebasewitharazorblade.Liquidcontentsofeachleafwerepouredintoa watch glass. The leafwas then slitlengthwiseand folded open. The solidcon- tents at the base ofthe leafwere removed with a spatula and placed in a vial containing 70% ethanol. Ninety-nine leaves wereprocessed from theMay 20, 1994 collections and an additional forty-seven leaves from the June 14, 1994 collections. Each sample was examined under low magnification and alderfly larvae wereremovedandplaced in separate vials. RESULTS A total ofeightalderflylarvaewereidentifiedin thecontentsofthe leaves. All larvae wererecoveredfrom theMay collections; none wasrecoveredfrom theJunecollections. Eachoftheplants sampled in May had atleastonelarvae in a leaf sample. Microscopic examination revealed dense mycelial growths attached tothemembranousareasofthe larvae.Thefungus was identified asa species ofSaprolegnia, a true watermold (Saprolegniaceae) (Coker, 1923). Although no adult alderflies were collected in May from the sweep netor beatingsheetsamples, several werecollectedinJuneincludingoneadultmale. The specimen was identified as Sialisjoppa Ross. Four species of alderflies have been recorded inWestVirginiaincludingS.joppa (Tartaretal., 1978). Vol. 107,No.3,May&June, 1996 139 DISCUSSION Pitcher plants are usually associated with bogs or swamps and are rather unusual becausethey exhibitpassivecarnivory.Anumberofreportsdocument that S. purpurea capture a broad spectrum of insect species as well as other arthropods (Rymal and Folkerts, 1982; Bradshaw and Creelman, 1984). Spe- cies found in the pitcher plant may be classified as inhabitants, prey, pitcher plant herbivores or occasional associates. Purplish/red nectar guides lead attracted insects up the brightly colored leaves to the lip where some ofthem fall into the water-filled reservoir below (Joel, 1986). Pitcher plants rely on a diversecommunityofbacteria,protozoaandinsectlarvaefordecompositionof trapped prey and absorption ofnutrients (Addicott, 1974). Alderflylarvaehavepreviouslybeenrecoveredfrompitcherplants. Mather (1981) recovered S. joppa larvae from a population of S. purpurea in New Jersey, one in late April and the other May 30. The collection dates for our material coincide well with the New Jersey collections. No fungal growth on the specimens was reported by Mather. There also was no indication of the numberofplants sampled. The presence ofeight sialid larvae in 99 leafcontent samples shows that sialid larvae are relatively common insects found in this population ofpitcher plants. Since the same species has now been found in two widely dispersed pitcher plant populations, it may be inferred that they are not rare in pitcher plants. Whether sialid larvae are prey is notclear. Five ofthe larvae exhibited dense growths ofSaprolegnia indicating the specimens were dead when col- lected. It is not known whether the other two larvae were alive or dead at the time ofcollection. Alderfliesaregenerallyassociatedwithbothloticandlentichabitats.Mather (1981) suggestedthatthelarvaemayhaveenteredthepitcherplant insearchof pupation sites. We suggest that in early spring the water level in the bog is higherdue to both snow meltandrain. During thattime sialid larvaedistribute throughoutthebog, somemoving intopitcherplant leaves where a rich source ofdead insects and live Diptera larvae can provide nourishment. As the water level recedes, the sialid larvae become stranded in the leaves. In March, 1995, weattemptedtotestthishypothesisbycollectingaquaticinsectsfromtheshallow waterinthevicinityofwherepreviouspitcherplantcollectionshadbeenmade. No sialid larvae wererecovered. Milesetai, (1975)reportedthatarelatedpitcherplantspecies, Sarracenia flava, producesanumberofnaturalproductsincludingtwoamines, an unusual enol diacetal monoterpene, sarracenin, andconiine, oneofthe poisonous alka- loids found in hemlock (Conium maculatum). The two amines are responsible forparalyzing insects afterthey become entrapped in the pitcher. Itispossiblethatconiine, sarracenin,orothertoxicaminesarepresentinS. purpurea. Theseorrelatedcompoundsmay immobilizeorkill sialid larvaethat 140 ENTOMOLOGICALNEWS enter the pitcher plants. The dead insects may subsequently be invaded by a species ofSaprolegnia which decomposes the larvae, providing nutrients for theplant. ACKNOWLEDGMENTS ThisstudywasaresultofasummerForest BiologyandEcology FieldCoursesponsoredby theU.S.D.A.-ForestService(EasternRegion)throughamemorandumofunderstandingwithHoward University.WethankBillWoodland,DistrictRanger,CheatDistrict,MonongahelaNationalForest forthecoordinationandlogisticalsupportofthefieldcourseandMaryBethAdams(ProjectLeader, SustainableForestEcologyInCentralAppalachianForests)forassistingwithteachinginthefield course.EcologicalReport#2. Wewould liketothankOliverS. 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