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15Volume62February2003TheBeginner'sGuidetoCaddis(OrderTrichoptera)byIanWallaceKeeperofInvertebrateZoology,NationalMuseumsandGalleriesonMerseyside,WilliamBrownStreet,Liverpool,L38EN.
IllustratedbyPhilWilkins(7607)PeregrineProductions,TheSummerhouse,OrfordRoad,Tunstall,SuffolkIP122JA.
AdultRhyacophilaseptentrionisAgapetusfuscipeslarvaincaseCaddislarvae,livinginacasetheyhavemade,aresomeofthemostfamiliarfreshwaterinsects.
TheyarethoughttoderivetheirnamefromElizabethanstreethawkerscalledcaddicemenwhosoldbraidandhadsamplesstitchedtotheircoats.
Whilethecommonnameforthegroupisderivedfromthelarva,thescientificnamefortheorder,Trichoptera,alludestothehairycoveringoftheadult'swings.
AfewspeciesrelyonthehairstoformthewingpatterninthesamewaythattherelatedLepidopterarelyonscales.
However,inthemajorityofcaddisthebrownorgreypatternofthewingsisinthemembraneandcannotberemovedbyrubbing,unliketheLepidoptera.
Thereare198BritishandIrishspeciesin18families.
EncounteringadultcaddisAsexpectedforaninsectwithanaquaticlarvalstage,youwillencounterthelargestnumberandvarietyofcaddisnearwater.
Manyspeciesflyintheearlynightandpassthedayrestingonbank-sidevegetationfromwheretheycanbedislodgedontoabeatingtray.
Howeveryouwillfindthat,byenergeticleaping,theywillsoonescapefromthetray,eveniftheydonotflyoff.
Beatingintoasweepingnetismoresuccessful.
Manydoformday-flyingswarmsoverthewaterandthemostfamiliararethelong-hornedcaddisofthefamilyLeptoceridae,whose16BulletinoftheAmateurEntomologists'Societyantennaefarexceedthebodylength.
Theyformzig-zaggingswarmsclosetothewatersurfaceafewfeetfromtheshore.
Theymaylookeasytocatchbuthavepositionedthemselvesacertaindistancefromthebank.
Asyoucarefullywadeouttowardsthemyoubecomethebankandtheyobliginglymoveawayfromyou.
Speed,luckandwetnetsandclothesaretheorderoftheday!
AdultMystacideslongicornisTriaenodesbicolorcaseandlarvaLeptoceruscineiformislarvaandcase.
Adultsalsocometolighttrap,evenatadistancefromwater.
Particularlycommonintrapsawayfromwaterarethecaddisthatbreedinsitesthatdryupoversummer,whichseasonispassedasanadult.
Theselong-livedinsectsdiapauseinvariousplacesofwhichbunchesofgreenashkeysareespeciallyfavoured–afactdrawntomyattentionbyDrJimO'ConnoroftheNationalMuseumofIreland,Dublin.
Adultcaddisareimitatedbyfly-fishermenandseveralhavebeengivenangler'snames.
IdentifyingadultcaddisAdultcaddiscanbepinned,orpreservedinisopropylalcohol,availablefromchemists.
However,theiridentificationistroublesome.
Despitehavingpatternedwings,onlyaboutathirdofspeciescanbeidentifiedusingwingpatternsANDtherearecurrentlynobooksshowingthepatternsanyway.
Examinationofthegenitaliaisnecessarytogettospecieslevelinmostcases,andtheonlyin-printguidecostsabout150.
Enlistingtheassistanceofanexpertistheonlypracticalsolutionformostbeginners.
EncounteringthelarvalcaddisAnywaterbody(exceptthosethataredryformorethansixmonthsayear,oraremoderatelypolluted,orworse)islikelytohavecaddislarvae.
Caddislarvaefallintotwocategories.
However,likethesplitbetweenmicro-andmacro-moths,itisnotentirelybasedontheirtaxonomy.
Thegroupsarethe"cased"caddis,whichmakeatransportablecase,andtheso-called"case-less"caddis.
Thelattertermisveryconfusingasmostliveinafixedshelter,withonlyfourBritishspeciesinonegenusbeingtrulyfree-living.
Caddislarvaeshouldbepreservedinalcoholsuchasisopropylalcohol.
MethylatedorSurgicalSpiritarepossiblebutnotidealastheygocloudyondilutionandhaveotherchemicalsthatcouldaffectthecolourpatterning.
IdentifyingthecaddislarvaWhereastherearenoeasycharacterstoidentifygroupsofcaddisadults,severalgroupsofcaddislarvaeareeasytorecognise.
However,eventhenidentificationtothespeciesrequiresamicroscopeandidentificationkeys,butfortunately,thelatterarecomparativelyinexpensive.
The"caseless"larvaeRhyacophilalarvaeareunmistakable.
Thesefree-livingpredatorsofrunningwaterhavegreenbodies,yellowandblackheadsandbunchesofreddishgillsalongthesidesofthebody.
Therearefourspecies.
17Volume62February200318BulletinoftheAmateurEntomologists'SocietyThreefamiliesliveinsheltersbasedaroundnets.
Hydropsychids,withtheirstrongthoracicplatesandbunchesofwhiteventralgills,createarathercoarsemeshedsievetocatchpiecesofplantorverysmallanimalsfloatinginthecurrentofstreamsandrivers.
Thereareninespecies.
Philopotamidshavewhitebodiesandorangeheadsandliveinasocklikenetinfastflowingwater.
Themeshisveryfineandcatchessinglecelledplants.
Therearefivespecies.
ThelastgroupofnetmakersarethePolycentropodidswholiveinbothstillandslowlyflowingwater.
Thenetsof12ofthe13speciesaretangletraps,andactlikeunderwaterspider'swebstoensnareotheranimals;theenigmaticEcnomustenellus,ouronlyrepresentativeofthefamilyEcnomidaealsofeedsthisway.
TheexceptioninPolycentropodidaeisNeureclipsisbimaculata,whosefrenchhornshapednetsactassievesforfloatingmaterial.
ThesecanbeconspicuousRhyacophiladorsalislarvaHydropsydesp.
larvaandnetWormalldiasp.
larvaandnetHolocentropuspicicornislarvaandnetNeureclipsisbimaculatanetThefinalgroupofsheltermakingcaddis,thePsychomyiids,areverysmallandgrazealgaefromthesurfaceofrocksinstillandflowingwater.
Theycreateatubetocovertheiractivitiesandthisendsup19Volume62February2003meanderingoverthesurface.
Tenspeciesliveinthiswayandafurthertwo,inthegenusLype,buildtheirtubesonsubmergedrottingwood,onwhichtheyfeed.
Lypesp.
larvaandtunnelThe"cased"larvaeThemajorityofcaddishavelarvaethatbuildtransportablecases,andwithexperience,manycanbeidentifiedtospecieslevel.
However,forthebeginner,adepressinglylargenumberarenotparticularlycharacteristichavingcasesthatcouldbebestdescribedasbeingmadeofsandgrains,orhaphazardlyconnectedplantmaterial,oramixtureofsandgrainsandincorporatedplantfragments,dependingonwhatisavailable.
Forthatreasonitisnotpossibletoprovidefeaturestoenableidentificationofmostcasedcaddislarvae.
However,afewareverydistinctive.
Themicro-caddisofthefamilyHydroptilidaehavecasesonlyafewmillimetreslongbutmostofthegeneramakedistinctivecasesandallarelaterallyflattened.
Mostspeciescannotbeidentifiedbeyondgenuslevel.
SelectionofHydroptilidaecasesLtoR:Hydrophilasp.
,Ithytrichiasp.
,Oxyethirasp.
,Tricholeicohitonfagesii20BulletinoftheAmateurEntomologists'SocietyAnotherverydistinctivegroup,andverycommononrocksinrunningwater,andoccasionallakeshores,arethesixspeciesofGlossosomatidae.
Theymaketheirroundedhumpedcasesofcoarsesandgrains.
Iftheventralsideisexamineditwillbeseenthatthetwocaseopeningsareidenticali.
e.
thereisnofrontandback,andthelarvausesbothalternatelyasfront.
ForsomeunknownreasononlytwospeciesarefoundinsouthernBritain.
Theygrazealgaeandfinesettledorganicmatterfromthesurfaceofrocks.
Severalothercaddismakehumpedcasesi.
e.
iflookedatfromtheside,thetopedgeoverhangsthebottomedge,evenafternormalcasecurvatureistakenintoaccount.
HumpedcasesofcoarsesandgrainsinsmallspringstreamsaremadebyApataniamuliebrisaspecieswithoutmales.
Thefemaleslayfertileeggswithoutneedofmating.
SimilaronesonstonylakeshoresareofApataniawallengreniwhichdoeshavethenormalarrangementofmaleandfemale.
CaseslikethisfromariverwillprobablybeCeracleaannulicornisor,ifsmoothduetobeingmadeofsmallsandgrains–Ceracleadissimilis.
Beingdislodgedthenwashedaway,isalwaysaproblemforcaddis.
ThisistackledbythethreespeciesofGoeridaewhichincorporatelargeballastgrainsintothesidesoftheircases.
BaresandybottomsmayappeartobeanexposedpositionforacaddislarvabutMolannahascaseextensionsthatcompletelyobscuretheheadfromabove.
ApataniamuliebriscaseAgapitusfuscipeslarvaincaseGoerasp.
caseMolannaaugustatalarvaandcasefrombelowandcrosssection21Volume62February2003TriaenodesbicolorcaseandlarvaInrivers,adistinctivesquaresectioncasewillbeofLepidostomahirtum.
IfitisfixedfirmlytoapieceofvegetationwiththelarvasittingwithoutstretchedlegstocatchpassingparticlesthenitwillbefromonePhrygaenasp.
caseSamplingaweedypondorlakeanytimefromautumntolatespringwillcollectchunkycasesthathavethepiecesofcutplantmaterialattachedtransversely,ratherthanlengthways.
AgroupoffiveLimnephilusspeciesmakethis"log-cabin"typeofcaseandoneofthem,L.
stigma,whichusesgrassblades,producesoneofthebulkiestofallcaddiscasesintheformofashaggybarrelshapeditem.
Someofthefinestcraft-skilledcaddislarvaeusecarefullycutpiecesofplantmaterialtomaketheircases.
Joiningpiecesinaspiralfashionispopular.
Ifthecaseislargeandthelarvahasapropensitytoleaveit,theinvestigatorwillhavefoundoneofthefivespeciesofthefamilyPhryganeidae.
IfthecaseissmallandslenderandthelarvawithinrowsitselfandthecasethroughthewaterbyvigorousbeatingofthefringedbacklegsthenthelarvawillbeTriaenodesbicoloriffromstillwater,orthegenusYlodesiffromrunningorbrackishwater.
Limnephilisstigmacaseoftheangler'sgreatearlyspringfliestheGrannomBrachycentrussubnubilus.
OlderGrannomlarvaehavecasesthatareroundedinsection.
Lepidostomaalsoconstructsacasewiththeposteriorendofsandgainsandcircularincross-section,andthatisalsothesituationforCrunoeciairroratathatinhabitstinytrickles.
LepidostomahirtumlarvaandcaseCrunoeciairroratalarvaandcaseBrachycentrussubnubilisyoungcaseAcaddiscaseismadeofatubeofsilkenthreadstowhichotheritemsareattached,andsomecaddisdispensewiththeexternalmaterial.
Leptocerustineiformismakesaslendercaseandrowsthroughthewaterofpondsandlakesusingitsfringedlegs.
AgroupofthreespeciesinthegenusCeracleathathavecasesmadeonlyofsilkfeedonfreshwaterspongeandoftenattachdisguisingpiecesofspongetotheircases.
Somecaddischangetoasilkcaselateringrowth.
ArelativeofLeptocerustineiformisstartswithsandgrainsthenabruptlychangestoonlysilk,andtheGrannomstartswithplantpiecesandendswithmainlyacaseofsilk.
Ceracleaalbimaculacase,withspongeattachedBrachycentrussubnubilisoldercaseandlarva22BulletinoftheAmateurEntomologists'SocietyAlthoughcasesmadeofatubeofsandgrainstowhichlongsticksareattachedaremadebyseveralspecies,twodeservesinglingout.
Bothhaveblackmarkedyellowheads.
IfthecaseissmallandthehindlegsofthelarvaareconsiderablylongerthantheotherlegsitwillbeofthegenusMystacides.
IfthehindandmiddlelegsareofasimilarlengthandtheheadisparticularlyblotchyitwillbeAnabolianervosa.
Itissaidthatthesticksassistthelarvatoholdstationagainststrongcurrentbutitwillprobablyalsomakeitharderforafishtoapproachcloseenoughtohooverupthelarva.
Mystocidesunigralarva,caseandfaceAnabolianervosalarvalcaseandfaceItisunfortunatethatBritain'scommonestlargecaddisLimnephiluslunatusdoesnothaveadistinctivecase,orheadpattern.
However,acaddisfromflowingwater,inastraightcaseofplantmaterialwithorwithoutsandgrainsatthefrontendandwithabandedhead,islikelytobeLimnephiluslunatus.
Limnephiluslunatuslarva,caseandface23Volume62February2003EncounteringcaddispupaeWhenfullgrown,allfree-livingandshelterdwellingcaddismakeacaseofstonesorplantdebris,attachedtoastoneorlargeplant,inwhichtopupate;casedcaddislarvaealsoattachtheircasesandthensealupbothends,apartfromsmallgrillestoallowpassageofoxygenatingwater.
Toemerge,theadult,stillinitspupalskin,cutsoutofthecaseorshelterusingspecialmandibles.
Itthenrapidlyswimstothesurfaceofthewaterorthebank,usingfringedlegs.
Itisassistedinreachingthesurfacebyabubbleofgassecretedbetweentheadultandtheskin.
Thishowevermakesthemappearasasilverybubblethatisveryconspicuoustofish.
Largenumbersofcaddisarepredatedatthistime.
Manyspeciesemergeatnightwhenthefishcannotseethem–butwaitingDaubenton'sbatscandetectthesejuicymouthfuls.
Asuccessfulindividualsplitsthepupalskin,theadultrapidlyemergesexpandingitswingsinafewsecondsasitwrigglesoutoftheskin,thenfliestoanearbybushtodryitswingsforafewminutes.
Thepupalshuckfloatsaway,anemptyhusk.
RearingcaddisItmaybedifficulttoidentifycaddisbuttheycanbeinterestingtokeep.
Donottrytorearanyofthefree-livingorsheltermakersunlessyouhavetheabilitytocreateastronguni-directionalcurrent.
Casedcaddiscanbekeptwithvaryingdegreesofsuccess.
Agoodgrouptostartwitharethosethatliveinponds,suchasthe"log-cabin"limnephilids.
Theywillusuallyeatdeadleavesoftreeslikesycamore–butdonotoverfeed,andalittleaerationmightbehelpful.
AnotherintriguingcaddistorearisGlyphotaeliuspellucidus.
Lookoutforjellyeggsonleavesoftreesthatoverhangpondsandditchesorinplaceswherepondsandditcheswillbewhenthewaterlevelrises.
OnlyoneotherBritishcaddislayslikethis–thelargeandsuperbNemotauliuspunctatolineatusofPupaofGoerasp.
Glyphotaeliuspelluciduslarvaandcase24BulletinoftheAmateurEntomologists'SocietyHighlandblanketbogs.
Keeptheeggmassmoistbutnotwetuntiltinydarklarvaecanbeseenmovingwithinthejelly.
Submergingitwillletthemescape.
Theyfeedondeadtreeleavesanditisusefultohavebothsycamore(forfood)andoak(forcasemaking);thecaseisaflataffair.
Collectleavesfromthepondratherthanfromthegroundastheywillhavebothlosttherathertoxictanninsanddevelopedthemicro-fungiandbacteriawhicharewhatthelarvaearereallyafterasfoodwhentheyeatleaves.
Thoughitiseasytorearmanycasedcaddislarvae,itissurprisinglydifficulttogetsuccessfulemergenceofanadultfromthepupalskin.
Itisbesttoplacethesealedupcasesintoashallowandnotverticaledgedbowlfilledwithwater,butalsolinedwithnettingupwhichthecaddispupacanclimb.
Eventhen,manyrefusetoemergeandbecomeeventuallywater-loggedanddieseveraldayslater.
Incidentally,Britain'sonlyterrestrialcaddis,EnoicylapusillaoftheWyreForestwoodlands,isalsodifficulttoreartotheadult,usuallydyingduringpupation.
EnorcylapusillalarvaandcaseAssistancewithidentificationDuetotheabsenceofcheapbooks,Iampreparedtoidentifyvoucherexamplesofcaddisadultsbutnotbulksamplesandonlyifaskedinadvanceofsendingmaterialplease.
Ineedtoscheduleworkcarefully!
Iamalsoabletoconfirmtheidentityofcaddislarvae.
AgainIwouldwanttodovoucherspecimensonly.
Iwouldpreferablywantthecollectortohavetriedtousetheavailablekeysfirst.
Afteralittlefamiliaritymanycaddisadultsandlarvaecanbeidentifiedinthefield.
Myaimistoincreasethepoolofpeopleinterestedin,andrecordingcaddis,ratherthanjustaddtothesumtotalofrecords,valuablethoughthatis.
CaddisRecordingSchemeThereisanationalcaddisdistributionrecordingschemeoperatedundertheauspicesoftheBiologicalRecordsCentre,CEHMonksWood,25Volume62February2003AbbotsRipton,Huntingdon,CambridgeshirePE282LS.
Detailsofhowtocontributerecords,theaimsoftheschemeandsomeofitscurrentprojects,canbeobtainedfromtheBiologicalRecordsCentre,orfromitsweb-siteorfrommepersonally.
FurtherreadingHickin,N.
E.
(1967)CaddisLarvaepublishedbyHutchinson,London(agoodintroductiontocaddislarvae,withsomelovelyillustrationsbutout-ofdateforidentificationoflarvae;thekeytopupaehoweverremainsserviceable)Macan,T.
T.
(1973)AkeytotheadultsoftheBritishTrichopteraScientificPublicationsoftheFreshwaterBiologicalAssociation,Number43.
(longout-of-print,andwithafewerrors,butworthobtainingifyoucan.
AlistofproblemsthatmightbeencounteredwhenusingMacanisavailablefromIanWallaceatLiverpoolMuseum)Malicky,H.
(1983)AtlasoftheEuropeanTrichopteraJunk,TheHague.
(veryexpensive,andasitcoversalltheEuropeanspeciesitisnotabookforthebeginner)Edington,J.
M.
&Hildrew,A.
G.
(1995)ArevisedkeytotheCaselessCaddisLarvaeoftheBritishIslesScientificPublicationoftheFreshwaterBiologicalAssociation,Number53(thedefinitivekeytoidentifycaselesscaddislarvae)Wallace,I.
D.
,Wallace,B.
&Philipson,G.
N.
(2003)ArevisedkeytotheCasedCaddisLarvaeoftheBritishIslesScientificPublicationoftheFreshwaterBiologicalAssociation,inpress.
(thedefinitivekeytoidentifycasedcaddislarvae)Wallace,I.
D.
(1991)AreviewoftheTrichopteraofGreatBritainResearchandsurveyinnatureconservationNo.
32,publishedbytheNatureConservancyCouncil,NorthminsterHouse,Peterborough,UK(adistributionsummaryforeveryBritishspecies;afewareoutofdatebutanupdateisavailablefromIanWallaceatLiverpoolMuseum.
)26BulletinoftheAmateurEntomologists'SocietyVisittheAESWebsitetoday!
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