Species Richness of Ferns and Associated Insects from Darjeeling Plains

5 Pages·1994·2.8 MB·English

by  A Mukhopadhyay

SPECIES RICHNESS OFFERNS AND ASSOCIATED INSECTS FROM
DARJEELING PLAINS1
A. Mukhopadhyayand D. Thapa2
Keywords: insectson fems, Darjeelingplains
A survey in the Datjeeling plains revealed someeighteen species offems,ofwhich,five were
common. Insectsfoundassociatedwiththecommonfemsweremostly Hemiptera(20spp.)andColeoptera
(19spp.)followedbytheLepidoptera(12spp.).Twopolyphagousspeciesof Orthopterawererecordedonthe
commonfems,DiplaziumandChristella. Somemicrolepidopteraandthysanopterawerefoundassociated
withthesporophyllsonly. Besidesaphytophagusspeciesofsawfly,threeotherHymenopterarecordedwere
parasitoids. The sole dipteran fly recorded was a laval-pupal parastite of the herbivorous lepidopteran,
Spilarctia scasigneta . Some ofthe fern attacking insects also occur on economically importantplants.
Introduction interspersed with fern vegetation. It is likely that
someofthefernassociatedinsectsmayswitchover
Femsareoneofthemostprimitiveplantsare tosuch economicallyimportantvegetation. Onthe
generallyconsideredasdifficultplantsforherbivores otherhand, thepossibilityoftheadjacentfernflora
to exploit (Eastop 1973, Hendrix 1977, Cooper- harbouring the natural enemies of the crop-pests
Driver 1978). Assuch,arelativepaucityofinsect- alsocannotbeoverlooked. Thereforewithaneyeto
herbivoresassociation with fems hasbeenreported the nature ofcontribution that the fern vegetation
(Schneider1892,Brues1920,Dethier1947,Ehrlich makes through insect-fem-crop interaction and
and Raven 1964). Swezey (1922) reported an alsotoexaminethehithertounknown insectfaunal
extensiveinsectfaunaof44 speciesassociatedwith communityofcommonfemsthepresentinvestigation
the fern floraofHawaiian Islands. However, only was undertaken.
one fourth of the insect species reported were
actually phytophagous (Weiczorek 1973). This Materials and Methods
underutilizationoffemsbyinsectshasbeenattributed
to host-resistant factors (Swain and Cooper-driver Amonthlysurveywasdoneduring 1988-90at
1973, Huffaker 1974, Hendrix 1977, Balick et al different sites, and the fronds were randomly
1978, Daniel and Chandrasekar 1986). However, sampled. The insects associated with the frondsof
the extensively sampled fern Pteridium aquilinum the common fems were either hand picked or
(L) Kuhn, isknown to supporta fair population of collected with the help ofan aspirator. They were
insectfauna(Lawton 1976,strongandLevin 1979). later etherised and oven dried before preservation
FurtherapioneeringquantitativestudybyBalicket for identification. The spotulating fronds were
al. (1978), showed that three Mexican ferns were collectedand broughtto thelaboratory wherethey
alsoextensively exploited by insects. were poisoned and pressed for herbarium
ThephytogeographicareaofDarjeelingplains preparation.
has a heterogenous vegetation. The forest, In caseoftheinsecteggsandlarvae,theferns
agroecosystem, teagardensareeitherflankedbyor on which they werefoundwere suppliedas food to
rearthemtotheadultstage. Thefemsaswellasthe
1AcceptedDecember1991. insect materials were identified by the Botanical
2EntomologyLaboratory,DepartmentofZoology,University SurveyofIndia,Zoological SurveyofIndiaand by
ofNorth Bengal,Dist. Daijeeling734430. othercompetent authorities.
SPECIESRICHNESS OFFERNSANDASSOCIATED INSECTS 87
Observations andResults thelarvalstagesofthespecies usedmaturingfronds
ofDiplazium andChristellaastheirfood.Pupation
The survey of fern flora and the associated tookplacein soil. Thelarvaeofthespeciesofthrips
insects of the common ferns was conducted (mentioned inTable2) were foundassociatedwith
extensively in the Darjeeling plains that was the sporophylls ofDiplazium
delimitedbyriverTeestaintheeastandriverMechi The natural enemies ofthe fern insects were
in the West. The ferns sofar recorded are listed in mainlyparasitoids. Thebrachonidparasitoidswere
Table 1. Ofthesethecommonlyfoundfernsbelong recorded from the larvae, while the chalcids were
to the genera Diplazium, Christella, Lindsea and recorded from theeggsofS. casigneta. The larvae
Microlepia.The insects associated with these ofS. casigneta werefoundtobeattackedbylarval-
common ferns were specially considered and pupalparasitoids. Theseweretheuzi fliespossibly
identifiedtounderstandtheirroleintheinsect-fem- belongingtothegenusExorista.Thelarvaeofthese
crop relationship. Of these groups of ferns, lepidopteranswhenrearedindoorwerealsoaffected
Diplazium had the largest number of insect by a fair infestation of these tachynid flies. The
herbivores,followedbyChristellaand Microlepia heteropteranbug,Eusarcocorisventralis,wasfound
(Table 2). Lindsea was abundant but no insect, toattack the lepidopteran larvaeofP. ustulalis.
attacking this fern, could be recorded. Some
specializedfeederslikesomemicrolepidopterawere Discussions
foundtoexploitthe sporesand sporangiophores of
Christella andDiplazium. Most ofthe lepidoptera Thelistoffern flora and its associatedinsect
larvae,includingtheeconomicallyimportantspecies, faunaisbasedonsurveyworkusingthemethodsof
used maturing fronds as food. Psara ustulalis random samplingatspotsselectedacrosstheentire
,
however, had the peculiarity ofrolling the apex of stretch ofthe Darjeeling plains. Although utmost
the mature fronds to make its own nest, where it carehadbeentakentorecordtheavailablespeciesof
ultimatelypupated. Whilealmostall theimmature ferns and the insects associated mostly with the
stages of the polygphagous species, Spilarctia commonferns,yetthelistmaynotbecomplete. The
casigneta was commonly recorded on Diplazium, chances of finding new fern species and their
naturaloccurrenceofS.obliqua wasmoresporadic associated insect forms can not beruled out in the
on thesame hostplant. elephant infested stretch of Terai woodlands and
Of the commonly occurring beetles, worth amongsttheepiphyticferns. Moreover,someofthe
mentioningwasthegreenweevil,Astycuslateralis, insect species occurring for very shortperiods and
which nibbled the maturing fronds and were also alsothosewhichare facultativefern-feeders,might
known toattacktea. Anotherpolyphagous weevil, havegoneunnoticed.
Myllocerus disolour, was common and had the ExaminationoftheBritishfern-feedinginsects
potentialitytoattach anumberofcrops (Table3). (OttossonandAnderson 1983)andcomparisonwith
Coloniesoftwospeciesofaphidsbelongingto amorecomprehensivelistbyHendrix(1980)revealed
differentgenerawererestrictedtotheventralsideof thatthepresentlistofthefern-associatedinsectsof
theyoungandmaturingfrondsofDiplazium Two Darjeelingplainshadmostoftheordersincommon
.
distinct species of mirids were found to be more excepting for Collembola and the phytophagous
associatedwithChristellathanwithDiplazium,and Diptera. Thefindingofthysanopterafromthe fern
unlike most other insects they attached the young faunaofNilgiriandAnnamalaihillsbyDanieland
coiled fronds. Amongstthe hymenopterans found Chandrasekar(1986)wascorroboratedbythepresent
associated as a true herbivore, a species ofsawfly, observation from this part of India, when the
Stromboceroscongener,needsspecialmention. All association ofthrips werealsorecorded with the
88 JOURNAL,BOMBAYNATURAL HIST. SOCIETY, Vol. 91 (1994)
Table 1 8. Manobiasp. tt
ALISTOFFERNSFROMDARJEELINGPLAINS 9. Monoleptasp. tt
10. Alticasp. tt
1. BlechnumorientateLinn. 1121.. ACfriyspstaodguomneoiulsi(spM.uls.) Coctctinellidae
2. Christellaappendiculate(Pr.)Holt. 13. Nanophyessp. Curculionidae
3. Christellaaridus(Holt).* 14. Alcidessp. tt
4. Christellacrinipes(HK)Holt.* 15. Astycuslateralis(F.) tt
5. Christellaparasiticus(L)Lev. 16. Myllocerusdiscolour(Boh) tt
6. CyatheaspinulosaWallHook.(TreeFern) 17. Phytoscaphussp.
18. Legriasp. Lagridae
7. Diplaziumesculentum(Retg)Sw.*
19. Species(indet) Elateridae
8. Dicranopterislinearis(Brum,f.)underus.*
9. LindseaensifoliaSw.*
10. Lygodiumflexuosum(L)Sw. Hemiptera
11. Macrothelypteristorresiane(Gaud)Ching 1. Macromyzussp. Aphididae
12. Microlepiaspeluncae(L)Moore* 2. Tinocallissp. ”
13. Onichiumsiliculosum(Desv.)C.Chn. 3. Cloviaconifera(Walk) Cercopidae
14. Pityrogrammacalomelanos(Linn.)Linx. 4. Typhlocybasp. Cicadellidae
15. PterissemipinnateLinn. 56.. BPeantthhriomgioanijaunfoerDriusgt.ineaFabr. ””
16. PterislaiauritaLinn. 7. Gargararobusta(Dist.) Membracidae
17. PterisvittataLinn. 8. Homoeocerussp. Coreidae
18. Lypterissp. 9. CletusbipunctatusWestw. tt
10. Leptocorisaacuta(Thunb.) tt
*Commonlyoccurringfernspecies. 11. GraptostethustrisignatusDist. Lygaeidae
12. Spilostethuspandurus(Fabr) tt
Table2
13. AgonoscelisnubilaFabr. Pentatomidae
ASPECIESLISFTROOFMIDNASERCJTESELAISNSGOCPILAAITNESDWITHFERNS 1154.. EErutshaerscioncaorgiusttvaetnatr(aFlaibsr)Westw. tt
16. Dysdercuskoenigii(Fabr) Pyrrhocoridae
InsectnameandOrder Family 17. IphitalimbataStal. ”
Leptdoptera 18. Chrysocorisstollii(Wolff.) Scutellenidae
21.. PCarloldoepniistarliiatuprlaac(Foadbord)oides(Guen) Nottctuidae 2109.. SSppeecciieessAB((Iinnddeett)) Mirttidae
3. Spodopteramauritia (Boisd)
4. Eriopussp. *t Hymenoptera
5. Spilarctiacasigneta(koll.) Arctiidae 1. Stromboceroscongenerknw. Tenthridinidae
6. Spilarctiaobliqua(Walak.) 2. Apantelessp. Braconidae
7. Spilosomasp. 3. SpeciesA(indet) Ichneumonidae
8. Diacrisiapunctata(Moore) 4. SpeciesB(indet) Chalcidae
9. Nacoleiavulgalis(Hampson) Pyralidae
10. Psaraustulalis(Hampson) ft ORTHOPTERA
11. Amatacyssea(Cramer) Qenuchidae 1. Atractomorphacrenulata(Fabr.) Pyrgomorphidae
12. Microlepidopteransp.(indet) 2. Phlaeobapanteli(Bolivar) Acrididae
COLEOPTERA
Thysanaoptera
1. Anthicussp. Anthicidae
2. Aphanipterasp. Buprestidae 1. Heliothripshaemorrhoidalis(Bouche) Thripidae
3. ChrysolinainconstansWied Chrysomelidae 2. Elaphrothripssp. Phlaeothripidae
4. Aspidomorphadorsata(F.) ft
5. Aspidomorphanr.indicaBoh. Diptera
6. Aspidomorphasanctaecrueis(F.) 1. Exorista(?) Tachynidae
7. Hoplasomaunicolour(Iu.)
SPECIESRICHNESS OFFERNSANDASSOCIATED INSECTS 89
Table3 sporophylls of Diplazium. However, most of the
FERN ASSOCIATED INSECT SPECIES ATTACKING CROPS representative species of the insect-fauna of fern
[ListpreparedafterNair(1975),Das(1965), observedinthepresentsurveyseemedtoberestricted
BanerjeeandHaque(1985)andlocalobservations! totheOrientalregion asthey hadlittle incommon
with thecomprehensivelistcomprisingtheelements
OrderandInsectName AlternateHostPlants
from otherparts ofthe world (Hendrix 1980).
Lepidoptera Thestudyoftheinsectfaunaoffernsisalsoof
Spilarctiacasigneta(Koll) Blackgram,sunflower, economic significance, because a number ofthese
Sunhemp.
species being polyphagous have the potentiality to
Spilarctiaobliqua(Walk) Jute,sesamum,castor,ladies switchoverandcausedamagetocropplants.They
finger,groundnut,linseed,
turmeric,sunflower, mayalsocontributeintermsofnaturalinsectenemies,
sunhemp,potato,sweet thatmaykeepthecrop-pestpopulationundercontrol
potato. (Ananthakrishnan etal. 1986). Itis only after the
Spodopteramauritia (Boisd) Rice,wheatfoliage,millets. correctidentificationthattheroleoftheUzifliescan
Hemiptera be understood. Ifthe fliesdo notattack silk-worm
AgonoselisnubilaFabr. Rice,wheat,millets, larvae they may be useful as a natural controlling
pulses,ber,tobacco. agentoflepidopteran pests.
Chrysocorisstollii(Wolff.) Leechi.
EusarcocorisventralisWestw. Sesamum.
Acknowledgements
COLEOPTERA
Astycuslateralis(F.) Tea,millets,jute,cotton, We
sunhemp. aregrateful totheU.G.C. for funding the
projectduring 1988-90. ThanksareduetoZoological
Myllocerusdiscolour(Boh.) Drumstick,rice,wheat,
millet,cotton,groundnut. SurveyofIndia(Calcutta),BotanicalSurveyofIndia
(Calcutta)andIndianAgriculturalResearchInstitute
Orthoptera
(New Delhi) for identifying the survey materials.
Atractomorphacrenulata(Fabr.) Tobacco,sunflower,jute.
WewouldalsoliketothanktheDirector,Centrefor
Thysanoptera
Life Sciences and the Head of the Department of
Heliothripshaemorrhoidalis
(Bouche) Citrus,tea,coffee. Zoology,N.B.U. forprovidingworking facilities.
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