Hymenopteran Parasitoids of Drosophila Breeding in Decaying Herbage (Diptera, Drosophilidae)

9 Pages·1997·4.1 MB·English

by  Monika Offenberg

NachrBl.bayer. Ent.46(111), 1997 11
Hymenopteran Parasitoids of Drosophila Breeding
in Decaying Herbage
(Diptera: Drosophilidae)
Monika OFFENBERGER and Albert KLARENBERG
J.
Abstract
Drosophilalarvaeandpupaeareusedashostsbymanyspeciesofparasitoidwasps.Duringtwo
Drosophila breeding seasons eight larval and three pupal hymenopteran parasitoid species of
Drosophilabreeding in decaying herbageand fungiwerecollected from plantand fungal baits
in a temperatewoodland in southernGermany. Mean rates ofparasitation in Drosophila were
0-13.1 %. Studies on host-parasite dynamics in Drosophila requires knowledge of exact host-
parasite relationships. For this purpose, we developed a new baiting technique by exposing
plant and fungal baits with larvae and pupae, raised in the laboratory, of a Single Drosophila
species to hymenopteran parasitoids in nature. Six parasitoid species could be assigned une-
quivocally to their host(s). Laboratory experiments showed that Trichopria aequata Jansson
(Diapriidae)coulddevelopinseveralDrosophilaspeciesbutwasmostrapidinD. limbata.Inthe
field,however,thisparasitoidwasrearedonlyfromD.limbatapupaeinplantbaits.AsT.aequata
was not reared from fungal baits containing D. limbata pupae, it is very likely that volatile
Compounds released by decaying plant material attract this pupal parasitoid.
Introduction
Drosophilalarvaeandpupaeareusedashostsbymanyspeciesofparasitoidwasps,22ofwhich
are found in Europe (CARTON et al. 1986, JANSSON et al. 1988). A prerequisite in assigning
these hymenopteran parasitoid species to theirhosts isa detailed knowledgeofthe Drosophila
naturalbreedingSubstrates.Althoughnumerousstudieshavebeenperformedondrosophilids
breeding in fruit, fungiordecaying plant material (JAMESetal. 1988;COURTNEY etal. 1990,
OFFENBERGER & KLARENBERG 1992a,b), knowledge of Drosophila's parasitic wasps in na-
tureisstill limited. Consequently, thehost-parasitoid relationshipsofmany Drosophila species
areobscureand this isoneofthemain constraintson determiningthesignificanceofdifferent
mean parasitation rates in drosophilid communities; these rates ränge between and 100 %
(CARTONetal. 1991,JANSSENetal. 1988,DRIESSENetal. 1990,GRIMALDI&JAENIKE1983,
SEVENSTER 1992). Therefore, it is essential to determine the complete host-spectrum ofeach
speciesofwaspand establishtheirpreferenceswithin this spectrum. Only withsuchInforma-
tion will it be possible to investigate the effect of parasitoids on Drosophila ecology. Recent
studieson theecologyofwild European Drosophila speciesand theirparasitoids (JANSSENet
al. 1988, DRIESSEN etal. 1990, van ALPHEN etal. 1991) have again demonstrated the impor-
tanceand valueofinvestigating naturalbreedingSubstrates. Bothdecayingplantsand macro-
fungi proved tobea rieh sourcefor various Drosophila species (SHORROCKS 1982, BURLA et
al. 1991, DAVIS & JENKINSON 1992, OFFENBERGER& KLARENBERG 1992a,b). Within the
qiiinaria group D.piJialerata MEIGEN appears to be predominantly a fungus breeder while
D. limbata von ROSERseems tobea specialistdecaying-herbagebreeder (HOFSTETTER 1992,
OFFENBERGER
1994).
Inthepresentstudy,theexactrelationshipofparasiticwaspstotheirdrosophilidhostswas
assessed by testing laboratory-raiseti larvae and pupae of either D. limbata or D. phalerata
exposed with theirSubstratetonatural populationsofparasitoids. Wearepresentinga check-
list of23 wasp species netted over or reared from baits, of which 11 parasitise Drosopliila.
12 NachrBl.bayer. Ent.46(1IT),1997
Material and Methods
FieldObservations: Hymenopteran parasitoids and drosophilids were collected in 1990 and
1991 inIsarauen,a flood piainforestnorthofMunichinsouthernGermany(48°N, 11°E;515m
above sea level; see OFFENBERGER 1994). Collecting was doneby netting overbaits offungi
orofdecayingherbage(OFFENBERGER& KLARENBERGER1992a,b). Fungusand decaying-
herbagebaitswereexposedforseveraldaysinthefieldandwerethenbroughttothelaboratory.
They were kept there for two months to sample all eclosing drosophilids and hymenopteran
parasitoids. The insects were killed and preserved in 70 % ethanol, dried and pinned. The
Hymenoptera were identified to family using van ACHTERBERG (1990) and SCHMIEDE-
KNECHT (1930), while the genus Lcptopilina (Eucoilidae) and its constituent species were
identifiedusingNORDLANDER(1980).OtherHymenopteraweresenttoexperienced taxono-
mistsforIdentification(seeacknowledgements).ThedrosophilidswereidentifiedafterBÄCH-
LI & BURLA (1985) immediately after collection.
Experimentalanalysis: PlantbaitsoiAngelicasylvestrisL.orHemdeummantegazzia)iwnSOMM.
etLEV.,and baitsofcommercialmushrooms,Agaricusbisporus (LANGE) PILAT,wereoffered
to 20 gravid females, either D. Iwihata or D.phalerata. These strains, which originated from
Isarauen, had been maintained in the laboratory for 5 to 14 months. The female flies were
removed from the baits after sufficient larvae and pupae had developed. The baits-infected
with larvaeand pupae from a Single Drosophila species-were then exposed to hymenopteran
parasitoidsontheforestfloorinIsarauenforoneday.Thebaitsweresubsequentlymaintained
inthelaboratoryandeclosinghymenopteranparasitoidsanddrosophilidswerecollected. The
sex ratio and the parasitoid developmental time, were recorded. Laboratory cultures of 13
DrosophilaspeciesweretestedforhostacceptanceoiLeptopilinaheterotoma(THOMSON)(reared
fromwild D.pJinlerata)and Trichoprianeqiiata (THOMSON) (from D. liinbata). Drosophila larvae
andpupaewereexposed inmalt-foodvials (LAKOVAARA 1969)and theparasitoidswereleft
in the vials until they died. Each vial contained at least 50 larvae and/or pupae. "Maximal
developinentaltime"andbodysizewereinvestigatedinT.neqiiata,asnobiologicalInformation
was available on this pupal hymenopteran Drosop^hila parasitoid (GRAHAM 1969). "Maximal
developmentaltime"oftheparasitoidwasdefinedasthetimebetweenthefirstcontactwiththe
hostand theparasitoid'seclosion. Thenumberofeclosingparasitoidswascounted. Bodysize
(lengthfromthehead tothetipoftheabdomen)ofbothfliesandwaspswasmeasured witha
graticule in binocularmicroscope toan accuracyof ±0.01 mm.
Statistics: Itwasnotdetermined whichwasphad emerged fromwhich host fly and therefore
Kendalls-TauBcorrelationcoefficientwascalculatedfromrandomlychosenpaircombinations
ofthebody sizeofDrosophila adults and eclosed T.aeqiiata. This procedure was repeated four
times on different paircombinations foreach Drosophila species. The Statistical program SPSS
(4.0) was used fortheKendalls-Tau B correlation.
Results
Hymenopteran Parasitoids from Decaying Plants: A total of23 wasp species in the families
Braconidae, Eulophidae, Eucoilidae, Diapriidae, Pteromalidae and Serphidae was caught or
reared from seven different bait types. Table 1 lists 189 wasps of those European parasitoid
speciesknowntouseDrosophilalarvaeorpupaeasahost.Inadditionthetableincludesspecies
of Drosophila species likely to be the hosts of particular wasp species because both host and
parasitoid emerged from the same type ofbait. On average, three wasp species eclosed from
plantbaits.MostparasitoidspeciesweremembersofthegeneraLeptopilina(Eucoilidae),Aphae-
rataandAsobara(bothBraconidae).MashedbananaattractedAsobaratabida(Nees)inparticular.
Pupal parasitoids were only collected in low numbers. The Drosophila parasitism rate inbaits
NachrBI.bayer. Ent.46(1IT), 1997 13
Table1. AcompilationofparasitoidhymenopterainGermanycollectedbynetting (n)orreared (r)
from different baits in 1990 and 1991. Potential host drosophilid species of the larval and pupal
parasitoidsinEurope,ifknown(datafromCARTONetal.,1986;JANSSENetal.,1988;DRIESSENet
al., 1990;vanALPHENetal., 1991; HARDYetal, 1992;OFFENBERGER, 1994;J.J.M. vanALPHEN
andM.FISCHER,pers. comm.),aregiven. Bold faced Drosophilaspeciesareknownhosts. Drosophila
species which were found in all samples of a given kind of bait in this study are underlined. In
addition,thedistributionoftheparasitoidsinEuropeisshown.Thenumberofsamplesaregivenin
parentheses.
HymenopteranSpecies N Bait PotentialDrosophilid Distribution
(Family) HostSpecies (Country)
LARVALPARASITOIDS
Leptopilinaheterotoma (THS.) 12- AS (5) BUS, FEN, FUN, IMM, KUN, MEL, CH, D, E, F,
(Eucoilidae) LIM.OBS, PAL,PHA,SUB, TES GB, I, NL, S
Leptopilinaaiistralis(BELIZIN) 12'^ AS (2) FEN, IMM,KUN, LIM, PAL, PHA, D, NL
(Eucoilidae) SUB, lES,TRA
Leptopilinafiinbriata(KIEFFER) T AP* (2) FEN, LIM, PAL, SUB D, NL,S
(Eucoihdae)
Tanycarpabicolor(NEES) 5-
(Braconidae)
Tanycarpagraciliformis(NEES)
(Braconidae)
AphaeratascaptomyzaeFISCHER
(Braconidae)
Asobara tabida (NEES)
(Braconidae)
Asobararufescens(FORSTER)
(Braconidae)
Pentapleurapiuuilio(NEES)
(Braconidae)
14 NachrBl.bayer.Ent.46(1/2),1997
composed of rotting AiigeUcnsi/lvestris was considerably lower in 1991 (2.8 %) than in 1990
(13.1 %). In 1991,noparasitoidswerecollectedfrombaitsmadeupofAcgopodiiimpodagrariaL.
or commercial mushrooms (Agarkusbisporiis). In addition the following ten hymenopteran
specieswereattractedtobaits(notlistedinTable1),butarenotknowntouseDrosophilaastheir
host: Diapriidae-Idioiypa nigriccps KIEFFER, Spilonücriis flavipes THOMSON; Eulophidae-
Chrysocharisviridis (NEES),Pcdobiiisaca)üha (WALKER);Pteromalidae-CorunaclavataWALK-
ER,DiapiarapetiolataWALKER;Platygerrlnis unicolorGRAHAM;Serphidae-Brachyserphuspar-
vulus NEESand Exallomjxwnsmanni KIEFFER.
HymenopteranParasitoidsofD. limbata andD.phalerata: Table2givestheresultsforthose
decaying-herbagebaitswhichproducedparasitoids.Sixhymenopteranparasitoidspecieswere
identified: Taiiycarpin bicolor (NEES) (Braconidae) and L. heterotoiua, both larval parasitoids,
developed in D. limbata and D.plialerata; the larval parasitoid Apiliaeretascaptomyza FISCHER
and the pupal parasitoid Trichopria aequata (Diapriidae) eclosed from D. limbata. Two pupal
parasitoids, Vrestoviafidenas (WALKER) and Spalangia erythromera Förster (Pteromalidae), uti-
lized D.phalerata as their host. No hymenopteran wasps emerged from non-infected control
baits of either decaying A. sylvestris (n=5) or mushrooms, A. bisporiis (n=10) nor from baits
infectedwithD.phalerata,whichwerecomposedofeitherA. bisporiis(n=10),H.mantegazzianinn
(n=5), or Impatiensglaiidtilifera ROYLE (n=2).
HostSpecificityofTrichopria aequata: BothL. heterotoma and Trichopriaaequatadeveloped in
allDrosopihilaspeciesoffered (Table3).Withsomeexceptions,e.g.D.fimebris,femalebiasedsex
ratioswereobserved forthewasps. Inall the Drosophila speciestested, T.aequata malesdevel-
oped more quickly than females. The difference in maximal developmental timebetween the
sexes ranged from 2.5 days in D. limbata to 7 days in D.fimebris FABRICIUS. Developmental
time of T.aequata in D. limbata was significantly shorter than in D. immigrans STURTEVANT
(U-Test; p<0.001) and also shorter than in the three other quiuaria species (D. kuntzei DUDA,
D.phalerata and D. transversa FALLEN: U-Test, p<0.05). T.aequata had a significantly shorter
development in hostspecies which produced more than 20 females than in those hostspecies
whichproducedfewerthan20females(U-Test,p<0.05).T.aequatabodysizeshowedaweak,but
significantlypositivecorrelationW\\.\\Drosophilabodysize(Fig.l.;KendalLsTauB=0.35,p<0.01).
Table2. Parasitoid hymenoptera thateclosed from differentbaits, exposed in Isarauen, with larvae
and pupaefromaSingleDrosophilaspecies. Maximaldevelopmentaltimes (mean±s.e.;days) ofthe
parasitoidsinthedifferent Drosophilaspeciesareshown. Forabbreviations,seeTable 1.Thenumber
ofsamplesofa givenbait isshown in parentheses.
Bait Hymenopteran Males Females
Species n Max.Dev.Time n Max.Dev.Time
D. limlnüa + AB (5)
D. limbata + AU (4) Trichopriaaequata 22 39.2±0.1 26
HM
D. limbata + (10) Aphaeretascaptomyza
LcptopiUnaheterotoma 1 27
Tauycarpabicolor 1 18
D. plmlernta + AB (5)
D, phalerata + AU (10)
HM
D. phalerata + (10) LcptopiUnaheterotoma 2 23
Spalangiaerythromera
Tanycarpabicolor -
Vrestoviafidenas 6 19.3±0.3
NachrBl.bayer. Ent.46(1/2), 1997 15
Discussion
Twenty-three hymenopteran species were recorded in Isarauen, southern Germany, ofwhich
eleven species are Drosophila parasitoids, eight ofthem attacking larvae and three pupae. The
numberofhymenopteranspeciesisofthesameorderofmagnitudeasinsouthernEnglandand
Holland respectively, where, nine and twelve species have been recovered (BAKER 1979,
JANSSENetal. 1988). However,morerecentlyvanALPHEN (1992)estimatedatleastnineteen
larvalandsevenpupalparasitoidHymenopterafordrosophilidsintheNetherlands.Incontrast,
hymenopteranparasitoidsofDrosophilnarerareinthenorthofEngland,ScotlandandSweden
(A.J.DAVISandG.NORDLANDER,pers.comm.).TheInterpretationofthesedataishampered
bydifferences in the intensities ofparasitoid sampling and the methods used. Therefore such
comparisons need rigid standardization.
Assigninghymenopteranparasitoidspeciestotheirhostscanbeapproachedusingdifferent
techniques.Astraightforwardtechniqueistonetthemover,orrearthemoutof,baitsornatural
SubstratesinfectedwithDrosophilalarvaeorpupae(CARTONetal. 1986,DRIESSENetal. 1990,
OFFENBERGER1994).Thismethod,however,niaynotalwaysbeveryefficientwhenthehosts,
thewaspsorbotharepresentatlowdensities.Butitcouldbeveryproductiveatlocationswith
high parasitism rates (see JANSSEN etal. 1988). The disadvantage ofcollecting parasitoids in
thiswayisthatitgivesnoInformationonparasite-hostrelationships;itonlygivesanindication
as to the number of Drosophila species that can potentially be parasitized (HARDYetal. 1992,
Table3. BreedingsuccessofLeptopilinaheterotoma and Trichopriaaequata indifferent Drosophila spe-
cies.Thenumberoffemaleparasitoidsgiventoacultureofeachflyspeciesisshowninparentheses.
ForTrichopriaaequata,themaximaldevelopmentaltime(mean±s.e.;days)afterthefirstcontactwith
theirhost isshown.
Leptopilinaheterotoma
Species Males Females Total Sex Ratio
D, kuiitzei(3)
16 NachrBl.bayer. Ent.46(1IT),1997
Body Size Drosophila (mm)
Fig.1. Bodysizes(mean±s.d.)ofTrichoprianequnta,apupalparasitoid,whicheclosedinthelabora-
toryfromfivedifferentDrosophilaspecies(meanofN-7individuals).ThenumberofeclosedT.aeqiiata
isgivenin parentheses.
OFFENBERGER1994).Parasitizedspeciesmaybeidentifiedbytheirpupae(Baker 1979,HOFF-
MEISTER 1992). However, not all drosophilid species have yet been described in this way.
Assessingparasite-hostrelationshipsinthelaboratorybymeasuringthesurvivalofparasitoid
speciesinaseriesofpotentialdrosophilid hosts(Table3)maybeindicative. However,thereis
still the Chance forartefacts. Only field observations give certainty.
We have shown that with a new technique, i.e. baiting with decaying-herbage or mush-
roomsVk^hich were infected with a Single Drosophila species, thedisadvantagesofthe methods
describedabovecanbeovercome.Theparasitoid waspscouldonlyuselarvaeand pupaefrom
the Drosophihi species in thebaitwhich had beeninoculated in thelaboratoryand thensetout
fornotlongerthanonedayinnature.Otherinsectspecieswhichareattractedtothebaitsinthe
fieldmay,however,layeggsonit;theycanbeexcludedashosts,sincethewaspsparasitizeonly
larvaeorpupae,(whichdonoteclosefromeggsbeforeonedaytime).Usingthisprocedure,two
parasitoidhymenopteranspecies, V.fidenasand T.aeqiiata,couldbeassigned unequivocallyto
their host(s) (Table 2). Four additional species, L. heterotomn, T. bicolor, A.scaptoim/zae and
S. erythromera, have been recorded earlier using Drosophila as host (CARTON et al. 1986, van
ALPHEN etal. 1991, HARDY et al. 1992). T. hicolor and A.scaptoim/zae were previously un-
known as D. limhata parasitoids. T. aeqiiata was only reared from Alliiim iirsimim L./D. liiubata
baits that were set out in Isarauen. In spring, Alliiim ursiniim is found in large patches in
woodlands and is a naturalbreeding Substratefor D. liiubata, which concentrates ondecaying
plants (OFFENBERGER& KLARENBERG 1992a, OFFENBERGER 1994). T.aequatawas reared
NachrBl.bayer. Ent.46(1/2), 1997 17
in the laboratory from a total of twelve Drosophila species. Maximal developmental time of
T.aeqiiatain D. limbata wasshorterthaninanyotherpotentialhostspeciesincludingtheother
European qiiinaria group species D. kuntzei, D.phalerata and D. transversa. Moreover, thebody
sizeofT.aeqiiatarearedinD. liiubatawaslargerthaninD. littoralisMEIGEN(Fig. 1).Thesedata
alsosuggestthatD. limbataistheprincipalhostotT.aeqiiata.L. heterotomaandT.aeqiiatashowed
female biased sex ratios in most drosophilid hosts (Table 3), which is the rule for many
hymenopteranparasitoids(HARDY1994).Howevertherewasoneexception,D./;/nd7ns,where
L.heterotomabreaks therulebyproducinganexcessofmales. Testswith L.heterotomashowed
thatall fourEuropean quinaria species weresuited fordevelopment. This is in contrasttovan
ALPHENetal. (1991)whoreportedthatL.heterotomadidnotsuccessfullyreproduceinD. limbata.
The causes for this discrepancy are unknown. However, our results agree with those of van
ALPHEN etal. (1991) and HARDY etal. (1992) that L.aiistralis (BELIZIN), L.fimbriata (KIEF-
FER) and L.heterotoma attack hosts in decaying plants.
Agariciisbisporus attracted only two individuals of Asobara tabida, whereas not a Single
individual was reared. Further tests will have to be performed to determine whether this
Substrateattractsparasitoid Hymenoptera. In theNetherlands fungus-breeding Drosophila are
parasitizedby L. clavipes (HARTIG) (DRIESSENetal. 1990). Thisparasitoidwas, however,not
attracted to commercial mushrooms but to stinkhorns {Phallus impudiciis PERSOON). The
absenceofstinkhorns in Isarauen maybethecause forthemissingofthis parasitoid fromour
collections. VETetal. (1984) havedemonstrated thatfemaleAsobaraand Leptopiliiiaspeciesare
attracted by substances released from the host breeding Substrate. WISKERKE etal. (1993)
showed that L. heterotoma uses the Drosophila adult aggregation pheromone. The experiments
withthefungusand decayingplantbaitsinoculated withDrosophilalarvaeand pupaeindicate
thatthetypeofSubstratemaybemoreimportantinattractingparasitoidsthan thehostlarvae
and pupae themselves. This suggests that volatile Compounds released by the Substrate are
involved inattracting theparasitoids.
Webelievethatthebaitingmethod withfixednumbersofDrosophilalarvaeorpupaecould
beused tomonitorparasitationratesofgivenhost-parasitoidcombinationsand toestimatethe
relative population density ofparasitoidsindifferent habitats. Moreover,differentstrainsofa
Single Drosophila speciesormixturesofdifferent Drosophila speciescould betested underfield
conditionswithrespecttotheirsuitabilityashostsforhymenopteranparasitoids.However,for
testingtherelationshipbetweenhostdistributionsandparasitoiddistributions(MAY&SOUTH-
WOOD 1990, PACALA & HASSEL 1991, GODFRAY 1994), our data are not suited. Such an
analysis could be very successful when large numbers of baits containing small amounts of
Substrate,whichmimicthesizeofthenaturalpatchesusedbyDrosophila,aresetoutinthefield.
These data shovild be compared with collections ofnatural patches used by the hosts.
Thedatafortheknownversuspotentialdrosophilidhostspecies(Table1)demonstratehow
scantyourknowledgeofhost-parasitoid relationships in temperatewoodlands ofEuropestill
is. It Stresses onceagain the need for morefield observations, inparticularwith respectto the
pupal hymenopteran Drosophila parasitoids.
Acknowledgements
WewouldliketothankC.vanACHTERBERG(RijksmuseumvoorNatuurlijkeHistorie,Leiden,The
Netherlands), I. WALL (Mühlingen,Germany),G.NORDLANDER(Swedish UniversityofAgricul-
turalSciences,Uppsala,Sweden)andM. DOGANLAR,(CumhuriyetÜniversitesi,Tokat,Turkey)for
theirkindsupportinidentifyinghymenopteranparasitoidspecies.WearegratefultoJ.vanALPHEN
(Dept.ofPopulationBiology,RijksuniversiteitLeiden,TheNetherlands)forhospitalitytoM.OFFEN-
BERGER, to E. DILLER (ZoologischeStaatssammkmgMünchen) formediationand to L. KERBTEN
for baiting Trichopria aeqiiata. Mrs. A.CLARK-OTT kindly corrected the English. For commenting
earlierversionsofthemanuscriptwethankA.DAVIS(Leeds),J.JACOBS(München),I.HARDYand
J. van ALPHEN (Leiden). Most of the identified wasps are given to Zoologische Staatssammlung
München.
18 NachrBl.bayer. Ent.46(1IT), 1997
Zusammenfassung
LarvenundPuppenvonDrosophilidenwerdenvoneinerVielzahlvonHymenopteren-Artenparasi-
tiert. Das Artenspektrum parasitischer Wespen wurde in zwei aufeinanderfolgendenJahren durch
regelmäßige Netzfänge über Ködern aus verrottenden Früchten, Kräutern und Pilzen bestimmt. In
den Isarauen bei München exponierte Köder und natürliche Brutsubstrate wurden im Labor nach
ausschlüpfendenTaufliegenundWespenabgesucht;diedarausermitteltenParasitierungsratenlagen
bei bis 13,1 %. Über den Einfluß parasitoider Hymenopteren auf die Populationsstruktur und
-entwicklungeinzelnerDrosof'/n7rt-SpeziessagensolcheDatenallerdingswenigaus.Vielmehrmüssen
dieexaktenZuordnungenvonWirts-undParasitenspeziesgeklärtwerden.DaherwurdeeineMetho-
deentwickelt,dieeindeutigeBrutnachweiseimFreilandermöglicht.MitderneuenTechnikgelangen
bei sechs Wespenarten Brutnachweise aus D. Uiubntn bzw. aus der nah verwandten D. pbalerata.
AnschließendeLaborversuchebestätigtendieTauglichkeitdieserundweitererArtenalsWirtefürvier
Wespenarten. Vrestoviafidenas (Pteromalidae), deren Biologie bisher unbekannt war, schlüpfte aus
Puppenvon D. phalerata; Trichopriaaequata (Diapriidae) konntesichin zahlreichen Drosophila-Arierx,
amschnellstenaberinD.Uiubafnentwickeln.ImFreilandlocktennurmitD.IbnbatabesetzteKöderaus
verrottenden Pflanzen, nichtjedoch solche aus Pilzen T. aequata an. Daraus läßt sich schließen, daß
Duftstoffeder Droso^)/7;7rt-BrutsubstratebeiderWirtsfindungmaßgeblichbeteiligtsind.
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AnschriftderVerfasser:
* MonikaOFFENBERGER
Isartalstraße24
D-80469München
Albert KLARENBERG
J.
ZoologischesInstitut
Karlstr.23
D-80333München