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Diversity and Commonality in Animals

Brain Evolution by Design

From Neural Origin to Cognitive Architecture

DiversityandCommonalityinAnimals

Serieseditors

TakahiroAsami Matsumoto,Japan

HiroshiKajihara Sapporo,Japan

KazuyaKobayashi Hirosaki,Japan

OsamuKoizumi Fukuoka,Japan

MasaharuMotokawa Kyoto,Japan

KiyoshiNaruse Okazaki,Japan

AkikoSatoh Hiroshima,Japan

KazufumiTakamune Kumamoto,Japan

HideakiTakeuchi Okayama,Japan

MichiyasuYoshikuni Fukuoka,Japan

ThebookseriesDiversityandCommonality inAnimalspublishesrefereedvolumes onallaspectsofzoology,withaspecialfocusonbothcommonanduniquefeatures ofbiologicalsystemsforbetterunderstandingofanimalbiology.Originatingfrom acommonancestor,animalsshareuniversalmechanisms,butduringtheprocessof evolution,alargevarietyofanimalshaveacquiredtheiruniquemorphologiesand functionstoadapttotheenvironmentinthestruggleforexistence.Topicscovered includetaxonomy,behavior,developmentalbiology,endocrinology,neuroscience, andevolution.Theseriesisanofficial publicationofTheZoologicalSocietyof Japan.

Moreinformationaboutthisseriesat http://www.springer.com/series/13528

Editors

BrainEvolutionbyDesign

FromNeuralOrigintoCognitiveArchitecture

Editors

Naples,Italy

TadashiNomura KyotoPrefecturalUniversityofMedicine Kyoto,Japan

ISSN2509-5536ISSN2509-5544(electronic) DiversityandCommonalityinAnimals

ISBN978-4-431-56467-6ISBN978-4-431-56469-0(eBook) DOI10.1007/978-4-431-56469-0

LibraryofCongressControlNumber:2016962454

©SpringerJapanKK2017

Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof thematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation, broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionorinformation storageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilarmethodology nowknownorhereafterdeveloped.

Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse.

Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthisbook arebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsor theeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinorforany errorsoromissionsthatmayhavebeenmade.

Printedonacid-freepaper

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TheregisteredcompanyisSpringerJapanKK

Theregisteredcompanyaddressis:ChiyodaFirstBldg.East,3-8-1Nishi-Kanda,Chiyoda-ku,Tokyo 101-0065,Japan

Preface

Thepresentbookisanew,detailedexaminationtoexplainhowelegantbrains havebeenshapedbysimpleprinciplesinevolution.Classiccomparativestudies haverevealedgreatdiversityofneuralnetworksandcomplexbehaviorsinmany animalgroups.Therecentintegrativemolecular,developmental,physiological,and psychologicalapproaches,however,haverevealedunexpectedcommonalityinthe basicstructuresandfunctionsacrossanimalphylogeny.Thestructuralframeworks ofthenervoussystemsandbrainsareoftenreplicatedinartificialintelligenceor machinesconstructedbyhumanactivities, suggestingthatfunctionalsimilarities provideacommondesignforinformationprocessingsystemsthroughbiophysical constraints.

Thebookintroducestheoriginofneuronswiththesingle-cellcreatureswithout neuronsandthengoesontoprimordialtypesininvertebratessuchascnidarians, flatworms,molluscs,insects,andchordates,withagreatabundanceofthebrains ofvertebrates:fish,reptiles,birds,andmammals,includingwhalesandhumans. Recently,anumberofresearchinvestigationsofdiverseandminororganismshave beenconducted,andweneedtokeepuptodate.Eachchapterprovidesprofessional anddetailedtopicsaboutbrainevolution;however,thisbookasawholeisarranged alongasimpleconcepttofindsomethingofcommondesign.Also,non-organisms suchasmodelsandmaterialsarecoveredtoexplorethedesignsintheoriginand evolutionaryprocesses,buttheyarenotcomprehensive.Thetopicsareprovidedin atimelymannerbecausenoveltechniquesemergedrapidly,forexample,asseenin next-generationsequencersandomics(e.g.,genomics,proteomics,metabolomics, andconnectomics)approaches.Withtheexplosionofbigdata,theneural-related genesandmoleculesarenowontheradar.

Importantly,nowtheneuralnetworkshavebeentakennoticeof.Forinstance, Europe’s A C1billionscienceandtechnologyprojects,suchastheHumanBrain Project,werelaunchedin2013toanalyzebrainconnectomics.Thebiginterdisciplinaryplan,theBlueBrainProject,alsoaimstounderstandthesmallmammalian brain.Furthermore,withtheriseofrecentlyadvancedartificialneuralnetworks, thereisenthusiasmforthedevelopmentofneuralnetworkmodels.Theviewsof brainevolutionprovideanessentialopportunitytogenerateideasfornovelneuron-

andbrain-inspiredcomputation.Forthatreason,thisbookwillshowthereaderhow toextractmeaningfulneuralstructuresinnature.

Forundergraduates,graduatestudents,andprofessionalscientistswhoseeka deeperunderstanding,thisvolumedemonstrateshowtofindthebasicprinciples shapingbrainsthatprovidedhighercognitivefunctionsinthecourseofevolution. Ourambitionisthatthebookwillstimulatestudents,particularlyyoungscientists, todelveintoproblemsremaininginthis discipline.Manyauthorswereselected fromyoungJapanesescientists,andthisworkispartofaseriesofpublicationsof theZoologicalSocietyofJapan.

Naples,ItalyShuichiShigeno Matsuyama,JapanYasunoriMurakami Kyoto,JapanTadashiNomura

Contents

PartITheOriginsofNeuronsandNetworks

1PhysicalEthologyofUnicellularOrganisms ............................3 ShigeruKuroda,SeijiTakagi,TetsuSaigusa, andToshiyukiNakagaki

2MolecularCharacteristicsofNeuron-likeFunctions inSingle-CellOrganisms ..................................................25 ShingoMaegawa

3BackThroughTime:HowCnidariansandBasal MetazoansShedLightonAncientNervousSystems ...................45 HiroshiWatanabe

PartIITheRiseofDiverseBrainTypes

4FunctionalSpecificationofaPrimitiveBilaterianBrain inPlanarians ................................................................79 TakeshiInoue

5TheComputationandRobustnessoftheMini-Cognitive CentersofTerrestrialMollusks:AnExquisiteOutcome ofBrainEvolution ..........................................................101 RyotaMatsuo

6InsectBrains:MinuteStructuresControllingComplexBehaviors ...123 MichiyoKinoshitaandUweHomberg

7IdentifyingVertebrateBrainPrototypesinDeuterostomes ............153 TakehiroG.Kusakabe

8GenomeandTranscriptome-WideResearchofBrainEvolution .....187 AtsushiOgura vii

PartIIICognitiveSystems

9TheOriginofVertebrateBrainCenters .................................215 YasunoriMurakami

10AdaptiveRadiationandVertebrateBrainDiversity:Cases ofTeleosts ....................................................................253 NaoyukiYamamoto

11MolecularProfilingRevealsInsightintoAvianBrain OrganizationandFunctionalColumnarCommonalities withMammals ..............................................................273 KazuhiroWada,Chun-ChunChen,andErichD.Jarvis

12TheNeocortexandDorsalVentricularRidge:Functional ConvergenceandUnderlyingDevelopmentalMechanisms ............291 WataruYamashitaandTadashiNomura

13MolecularInvestigationsoftheStructure andDevelopmentoftheBrainofCarnivores ............................311 YoheiShinmyo,TomohisaToda,KosukeMasuda, YoshioHoshiba,HarukaEbisu,NaoyukiMatsumoto, andHiroshiKawasaki

14EvolutionoftheMammalianBrainwithaFocus ontheWhaleOlfactoryBulb ..............................................329 TakushiKishida

15TheEvolutionandFunctionofSleep .....................................343 YuHayashiandChih-YaoLiu

16PrefrontalAnatomicalArchitectureandTop-Down BehavioralControlinHumanandNonhumanPrimates ..............367 YosukeMorishima

PartIVModelsandDesigns

17OrganisationalPrinciplesofConnectomes:Changes DuringEvolutionandDevelopment ......................................387 RomanBauerandMarcusKaiser

18Muscular-HydrostatComputers:PhysicalReservoir ComputingforOctopus-InspiredSoftRobots ...........................403 KoheiNakajima

19BrainEvolutionasanInformationFlowDesigner:The GroundArchitectureforBiologicalandArtificialGeneral Intelligence ..................................................................415 ShuichiShigeno

Chapter1

PhysicalEthologyofUnicellularOrganisms

ShigeruKuroda,SeijiTakagi,TetsuSaigusa,andToshiyukiNakagaki

Abstract Inthischapter,somebehavioursofunicellularorganismsthatappear tobesmartorintelligentarereported.Twotopicsarethefocusfromtwomajor groupsofeukaryoticunicellularorganisms,amoebaeandciliates: (1)anticipatory capacityofperiodicenvironmentaleventsinanamoebaand(2)environmentinduceddevelopmentofanewtypeofbehaviourinaciliate.Amechanismofthese behavioursisdiscussed,basedonamechanicalequationofmotion.Ethology(the scienceofanimalbehaviour)ofunicellularorganismsisrecentlybeingstudiedfrom aphysicalpointofview.Weproposetocallthiskindofstudy fphysicalethologyg. Physicalethologymaygiveussomehintsabouttheoriginofprimitiveintelligence.

Keywords Ciliate•Learning•Adaptability•Primitiveintelligence• Membraneexcitability•Ethology•Nonlineardynamics

1.1Introduction

Thecellisthebuildingblockofallorganisms,whichcanbetheminimumsetof life,becausethecellisnotaliveifitisdividedintosubsystems:thisimpliesthatall essencetobecommonthroughouttheentirerangeoforganismsmustbefoundin acell.So,thecellistheinterfacebetweenanassemblyofmerelymaterialsandthe functionalstatesoflivingsystems.

Infact,manykindsofsmartbehaviourthatlooklikeaprimitiveformofintelligenceinsomesensehavebeenreportedandcomparedwithso-calledintelligent behavioursinhigheranimals(Jennings 1906;Bray 2009;Eisenstein 1975;Corning andVonBurg 1973;Trewavas 2003, 2005).

S.Kuroda( )•T.Nakagaki

PhysicalEthologyLaboratory,ResearchInstituteforElectronicScience,HokkaidoUniversity, Sapporo001-0020,Japan

e-mail: nakagaki@es.hokudai.ac.jp

S.Takagi

FacultyofComplexandIntelligentSystems,FutureUniversityHakodate,Hakodate,Japan

T.Saigusa

DepartmentofCellularPhysiology,InstituteofNephrology,NiigataUniversity,Niigata,Japan

©SpringerJapanKK2017

S.Shigenoetal.(eds.), BrainEvolutionbyDesign,DiversityandCommonality inAnimals,DOI10.1007/978-4-431-56469-0_1

Althoughthelistofsuchbehavioursisgettinglongerandlonger,themechanism ofthesmartnessisbeingstudiedfromamechanicalpointofview.Thisisanattempt tounderstandanoriginoforganismicsmartnessinnatureandisanexcitingproblem tobetackledbytrulyinterdisciplinaryscienceinthiscentury.Here,wewishtoshed lightontheattempt.

Twooftheimpressiveexamplesaremazesolving(Nakagakietal. 2000, 2001; Teroetal. 2006, 2007)andanticipatingperiodicevents(Saigusaetal. 2008)by amoebae. Physarum,whichrecentlyhasbecomeafocusasaninterestingmodel organism,isahugeamoebathatconstructsatransportnetworkofinformation andmaterialsandmimicsananthropogenicnetworkofpublictransportation.This descriptionimpliesthattheremaybeacommonnatureofnetworkformationshared bymanand Physarum (Teroetal. 2010).

Theotherexampleofsmartbehaviouristheenvironment-induceddevelopment ofnewtypesofbehaviourinaciliate(Kunitaetal. 2014).Inthebehaviourofa ciliate,swimmingactivityisregulatedbymembranepotential(Naitoh 1990),and anequationofmotionforthemembrane potentialisdescribedbythereaction–diffusionequationoftheHodgkin–Huxleytype,whichwasoriginallyproposedfor thesquidneuron.Becauseofthesimilarityofexcitabilityofmembranepotential, theciliateisoftenstudiedasamodelsystemofneuronalactivity(Eisenstein 1975; Naitoh 1990).

Sofar,theattemptstoseekforaphysicaloriginofsmartbehavioursarejustat thebeginning,butthislineofstudy,whichweproposetonamephysicalethology, isexcitingandpromisingforthefuture.

Inthischapter,asanintroductiontothephysicalethologyofacell,wedescribe inmoredetailoneofthesymbolictopicsratherthantheoriginalreportalready studied:“Physarum anticipatesperiodicevents”(Saigusaetal. 2008).Althougha mathematicalmodelforanticipatorybehaviourwasproposedanddiscussed,wedo notrepeatithere.[Pleaseseethereference(Saigusaetal. 2008)forexplanationof themodel,whichsuppliesthemainbodyofthischapter.]

Afterthat,webrieflymentiononemoretopicoftheswimmingbehaviourof ciliatesbecausetheciliaaretheothermaincharacterofProtozoaaswellasthe amoebas.Anewkindofsmartbehaviourinciliates,reportedrecentlyin2014 (Kunitaetal. 2014),isdescribedinshortasasummary.Themechanismisreduced tothedynamicsofmembranepotentialthatcontrolsthebeatingactivityofthecilia. So,thisisanothertypicalexampleofphysicalethology.

Attheendofthischapter,someconcludingremarksaregivenonthepossible originofintelligentbehaviourthathasemergedatthelevelofasinglecell.

1.2AnticipatoryandRecallBehaviourinResponse toPeriodicStimulationinthePlasmodiaof Physarum polycephalum

1.2.1OverviewandBackground

Wereportonadaptiveresponsestoperiodicstimulationin Physarumpolycephalum (Mycetozoa),whichexhibitsprimitive anticipatoryandrecallbehaviour.The behaviourstudiedhereinvolvedthespontaneousperiodicslowdownofmigration justafteraseriesofperiodicstimulationshadbeenexperienced(anticipatory behaviour).Thisslowdownsubsequentlydisappearedbutthenreappearedaftera singlestimulation(recallbehaviour).Thebehaviourdisplayedwascharacterized bythefollowingfeatures.(1)Theanticipatoryslowdowndependedonthesize ofthebody.(2)Theresponsevariedacrossdifferentpartsofthebody.(3)Recall behaviourappearedeveninorganismsthathadfailedtodisplayanticipationearlier. (4)Thecellularrhythmofthecontractionmovementwasmuchslowerduring boththespontaneousslowdown(anticipation)andrecallbehaviourthanduringfree locomotion;thesameresponsewasshownduringtheslowdowndirectlyinduced byexternalstimulation.Theresultsobtainedheregivenewinsightabouthowthis abilityofanticipationandrecallemergesatthecelllevel.

Therepetitionofaparticulareventoftenleadstotheformationofmemoryand learninginorganisms.Forexample,aftermicewerefedseveraltimesatregular intervals,theylearnedtoanticipatethenextfeedingtime(RobertsandChurch 1978; Church 1978;Mecketal. 1984).Whenbeesweregivennectarat9:00a.m.every day,theygatheredatthescheduledtimeevenifnectarwasnotgiven(Gouldand Gold 1988).Theseareelegantexamplesofanticipatorybehaviourtowardsperiodic events.

In2008wereportedthatsuchbehaviourcanbeobservedeveninasinglecell, despitetheabsenceofanybrainornervoussystem(Saigusaetal. 2008).Similar behaviourscouldbeobservedinotherprotozoa(Brepharisma)andaplant(Chara) (Kunitaetal. 2013),buttheanticipatorybehavioursinthesespecieswerenot soclearasstatisticalfluctuationswerelargeandtheorganismsoftenfailedthe anticipation.Thus,furthercharacterizationisneededasthisfindingisinteresting fromanevolutionarypointofviewandgivesahintastothecellularoriginof primitiveintelligence(Ball 2008).

Theanticipatorybehaviourreportedinthepaperby(Saigusaetal. 2008)isas follows.Theplasmodiumofthetrueslimemould Physarumpolycephalum moves rapidlyunderfavourableconditions,but stopsmovingwhenexperiencingless favourableconditions.Plasmodiaexposed tounfavourableconditions(lowtemperatureandlowhumidity),presentedinthreeconsecutivepulsesatconstantintervals, werefoundtoreducetheirlocomotivespeedinresponsetoeachepisode.When subsequentlysubjectedtofavourableconditions,theplasmodiaspontaneously reducedtheirlocomotivespeedatthepointintimewhenthenextunfavourable episodewouldhaveoccurred.Thisfindingimpliesthattheplasmodiacananticipate impendingenvironmentalchange.Afterthisbehaviourhadbeenevokedseveral

timesinthecourseoffavourableconditions,thelocomotionoftheplasmodia returnedtonormal;however,theanticipatoryresponsecouldsubsequentlybe inducedagainbyasingleunfavourable pulse,implyingrecallofthememorized periodicity.

Tofocusondeviationandfluctuationofresponse,weaddednewexperiments andanalysedthedeviationbyreexaminingalargesetofdatathatincludednotonly thenewdatabutalsothepreviousdata(Saigusaetal. 2008);thisisthefirstpointto beconsideredhere.

Thesecondpointisdependencyontheinternalconditionsofthecell.In general,behaviouralresponsestoenvironmentalconditionsdependontheinternal conditionsofthecell,but littleisknownaboutit.So,wewilltestthepossiblefactors ofcellularconditions:sizeofbody,spatialinhomogeneityinpartsofalargebody, andeffectsonrhythmiccontractionofthecell.

Westudyfurtherdetailsoftheanticipatorybehaviourandreportseveralnew findingsandinsights.

1.2.2MaterialsandMethods

OrganismsandCulture Theplasmodiumof Physarumpolycephalum (wildtype) wasculturedusingoatflakesonanagarplateinarectangularplasticdish (25 35cm2 )at26 ı Candhumidityof90%accordingtoconventionalmethods.

ObservationofLocomotionVelocityUnderPeriodicChangesinAtmospheric TemperatureandHumidity Thetipportionofthelargeculturedorganismwas cutoutandplacedattheendofanarrowrectangulararea(0.5 28cm)onthe agarplate,hereafterreferredasanarena,asshowninFig. 1.1a.Thewetweightof theplasmodialmassthatwasinitiallyplacedinthearenavariedfrom5to40mg, dependingontheparticularexperiment.Thearenacontainingthespecimenwaskept inthedarkinanincubator(KCL-10000;Eyela)inwhichtheatmospherichumidity andtemperaturewerecontrollable.Themigratingorganismwasilluminatedfrom belowbyamatrixofinfraredLEDsandviewedbyaCCDcamera.Underthe cultureconditionsused,theplasmodiumstartedtomovetowardstheotherendof thearenaapproximatelyhalfanhourlaterandwasallowedtomovefreelyfor4h. Theatmospherictemperatureandhumiditywerethenchangedto23 ı Cand60% for10min,conditionsthatrepresentthestimulation.Thisstimulationwasrepeated threetimesatintervalsof £ (£ D 30,40,50,60,70,80,90min).Thepositionofthe extendingfrontofthemigratingplasmodiumwasmeasuredevery10min;typical timecoursesofthetippositionareshowninFig. 1.1b.

TypicalResponseAnalysedinThisStudy,OriginallyReportedin2008(Saigusa etal. 2008) Atypicaltimecourseofspeedandaccelerationofmigrationaswell asthetimecourseoftemperatureandhumidityareshowninFig. 1.1c,asreported inthepreviouspapers.Accordingtotheterminologyusedinthepreviouspaper,the periodicstimulationswerenumberedfromS1toS2andS3(indicatedbygraybars),

Number of lane (d) 1 2 3 4 5 6 ...

Fig.1.1 Schematicillustrationofexperimentalsetupsusedtostudy Physarum.(a)Illustrationof migrationalonganarrowlanefrombottomtotop. Arrow indicatesthefrontaltipoftheorganism, thepositionofwhichwasusedtocalculatelocomotionspeed.Arenasizewas0.5 28cm2 . (b)Typicalplotoftippositionwithrespecttotime.Theplothasbeencutintosectionsof 60minthatarestackedvertically;eachsectionincludesthepreceding60min(plottedasnegative time)tohelprecognizeperiodicresponses.Forinstance,theline a–b isidenticalto a0 –b0 .The columncolored grey indicatesthetimesatwhichstimulationoccurred.(c)Typicaltimecourse forlocomotionspeedinresponsetoperiodicstimulation. Blackarrows indicatespontaneous slowdown(SPS)attimeswhenthenextstimulationwouldhaveoccurredifcontinuedperiodically. Thewetweightoftheinitiallyinoculatedorganismwas15mg.Speedand accelerationwere averagedevery10min.SnandCnweretimingofactualstimulationandthefollowingperiodic timing(nostimulation).Thisresponsewasoriginallyreportedinthepreviouspaper(Saigusaetal. 2008).(d)Setupforthe‘comb’experimentinwhichthearenawasshapedlikeacombwith12 teethintowhichtheplasmodiumcouldextendapseudopod-likeprotrusion.Themigrationspeed wasmeasuredalongeverytooth.Toothsizewas0.5 25cm2

andthefollowingperiodicpointsintime(nostimulationwasapplied)wereC1,C2, C3,andsoon(indicatedbydashedrectangles).InC1andC2only,thelocomotion speedoftendecreasedspontaneously,sothisresponsewascalledspontaneousinphaseslowdown(SPS)hereafter.

AnArenawithComb-likeShapeDesignedforTestingInhomogeneity ofResponseOvertheWholeBody Anotherarenaintheformofacombthat consistedofmanyparallelslendercorridorswithacommonbasewasprepared (Fig. 1.1d).Thelargeplasmodiumwasplacedinthebaseandstartedtoextend alongthemanycorridorswhileremainingasasingleentity.

SpatiotemporalObservationforRhythmicContraction Accordingtotheconventionalmethod(TakagiandUeda 2008),wemeasuredcontractileactivityinthe plasmodium.Theplasmodiumwasilluminatedbythe20 20matrixofinfrared lightemissiondiode(wavelength,920nm)frombelow,andwasviewedfrom abovebytheblack-and-whiteCCDcamera(spatialresolution,480 640;time resolution,1/30s).Asthegraylevelofthevideoimagereflectedthethickness oftheplasmodiumthatchangedperiodicallywithaccompanyingtoactiverhythmic contraction,adarkerpixelindicatedathickerpartofplasmodium.Therelationship betweenopticaldensityontheimageandtherealthicknessoforganismwas standardizedbythecalibration.Weusedthestandardfreesoftwareforimage analysisImageJthatwaspreparedbytheNationalInstitutesofHealth(USA).A spatiotemporalpatternofoscillationperiodswasvisualizedasshowninFig. 1.6.

1.2.3Results

EffectofBodySizeonAnticipatoryBehaviour Figure 1.2 showsaveragedtime coursesofthemigrationspeed.Theplasmodiathatwereinitiallyinoculatedvaried inwetweight,andthedifferenceinbodysizewasclassifiedintothreegroups: 5–9mg(n D 27),10–19mg(n D 68),and20–40mg(n D 21).Theinitialspeed beforestimulationwassimilarforallthreegroupsbutdifferedafterstimulation. Althoughthegroupwithlargebodysizerecovereditspreviousmigrationactivity afterstimulation,thegroupsofmediumandsmallbodysizedidnotmoveasfast asbeforestimulation.Thisfindingimpliesthatstimulationcausedseriousdamage tothesmallerorganisms.Inthegroupwithbodysizefrom5to9mgwetweight,

Fig.1.2 Confirmationofanticipatorybehaviourin Physarum obtainedbymeasuringaveraged speedoflocomotion.Differentbodymasseswereinitiallyinoculatedforthethreetimecourses shown:small(5–9mg, n D 27, lowerline with rectangular symbols),medium(10–9mg, n D 68, middleline with circularsymbols),andlarge(20–56mg, n D 21, upperline with triangular symbols).AnticipatorybehaviourisobservedatC1andC2.Mean ˙ standarderrorofmean. Statisticalsignificanceofdifferencewastestedbypairwise t testwithBonferronicorrection(a methodofmultiplecomparison).The p valuewaslessthan0.001betweenthesmallandthelarge, andbetweenthemediumandthelarge,atthetimepointsofC1andC2,andbetweenallpairsatC3

someplasmodiadidnotmigrateatallafterthefirststimulation(datanotshown). SuchcaseswereexcludedfromtheresultsshowninFig. 1.2 and21experiments whenfinallyaveraged.Whenstrongerstimulationwasapplied(forexample,18 ı C and50%humidity),evenlargerplasmodiaweredamagedbyasinglestimulation.

Thespontaneousslowdownresponsethatwasobserveddependedonabalancebetweenbodysizeandthemagnitudeoftheenvironmentalperturbations. Anticipatorybehaviourwasshowninallthreegroupsatthetimesofthefourth (C1)andfifth(C2)virtualstimulations.Theanticipatoryresponsewasclearerfor smallerplasmodiabecausetheratioofthemigrationspeedsinthetwophases ofslowdownandrecoverywashigherthanforlargerplasmodia.Thesmaller organismsdemonstratedcleareranticipationbutsufferedmoreseriousdamage.The anticipationcapacitythusdependsonbothinternalandexternalconditions.

ResponseinLocalPartsoftheBody

Figure 1.3 showstimecoursesofthemigrationaccelerationforthecomb-shapedplasmodium(seeMaterialsandMethodsfor details).Thelanenumbersindicatedifferentpartsofthebodycorrespondingto different‘teeth’ofthecomb-shapedarena.Afterstimulationhadbeenappliedat timesS1,S2,andS3,anticipatorybehaviourwasexpectedattimesC1,C2,andC3. Anticipatorybehaviourwasindeedobservedastheoveralltendency(blacksquares indicatedeceleration).However,theexpectedresponsewasnotalwaysobservedin individuallanes.Forexample,itwasabsentinlanes1–3,7,and10atC1,andpresent inlanes,6,8,9,and11.Thevaryingbehaviourbetweendifferentlocalpartsofthe bodyimpliesthattheanticipatoryresponseissubjecttofluctuationsanduncertainty. Thiscomb-typeexperimentwasrepeatedthreetimes,andsimilarinhomogeneityof responsewasobservedinlocalpartsofthebody.

ResponsetoDifferentPeriodsofStimulation

Figure 1.4 showstheoccurrenceof spontaneousslowdowninresponsetovariousperiodsofstimulationintherange30–90min.Inallcases,theperiodicstimulationwasappliedthreetimes(S1,S2,andS3) andthetimeaxiswassettozerowherethelaststimulation(S3)wasgiven.Thefirst, second,andthirdoccasionsofvirtualstimulationareindicatedbyC1,C2,andC3, respectively.AtC1,thestatisticaloccurrenceofslowdownwashigh(10%–50%) forallperiodsofstimulation.Thebaselineoccurrenceofslowdownintheabsence ofstimulationwasapproximately10%.AtC2,ahighoccurrenceofslowdown

Fig.1.3 Accelerationasafunctionoftimefordifferentlanesofthecomb-shapedarena.The grey squares indicatepositiveaccelerationandthe darksquares indicatebraking

Fig.1.4 Anticipatoryresponseforstimulationperiodsrangingfrom30minto90min.The grey scale indicatesthestatisticaloccurrenceofspontaneousslowdown.Zerotimewasdefinedas thetimewhenthelaststimulationS3wasapplied.Spontaneousslowdownwasdefinedtooccur whenacceleration 0.2mm/(10min).Thenumbersofrepeatedexperimentsforeachstimulation periodwere36(30min),46(40min),34(50min),121(60min),40(70min),67(80min),and 39(90min).Thewetweightoftheorganismwas10–19mg.Datathatwerealreadyusedinthe previouspaper(Saigusaetal. 2008)wereincludedinthisanalysiswhilewesupplementednew dataof97repeatstomakethisnewanalysisoffluctuationsufficientlyreliable.Weanalyzedallthe data,notonlythepreviousonesbutalsothenewdata

wasstillobservedalthoughthetimingoftheresponsewassometimesshifteda littleearlierorlater.AtC3,theanticipatoryresponsewasnolongersignificantas thetiminggreatlyfluctuated.Ineachexperimentforagivenstimulationperiod, therewasadegreeofdeviationinthetimeatwhichspontaneousslowdownwas observed.Theanticipatoryresponseswereoftenadvancedordelayedbyasmuchas aquarterofaperiod,whichcanbeseenasacharacteristicofthistypeofbehaviour. Nevertheless,thereisacleartendencytowardsahighprobabilityofoccurrence alonglineC1inFig. 1.4.Weconcludethatanticipatoryspontaneousslowdown occurredforawiderangeofperiodsfrom30minto90min.

RecallBehaviourWithandWithoutAnticipatoryBehaviour

Figure 1.5 shows timecoursesofslowdownoccurrenceandaveragedspeedinresponsetoasingle stimulationthatwasapplied5haftertheseriesofthreeperiodicstimulations. AftertheanticipatoryresponseatC1,thelocomotionspeedquicklyreturnedtothe valuethatithadbeforethesequenceofstimulations.Afurthersinglestimulation wasthengivenatS4.Inresponse,spontaneousslowdownwasdisplayedatC6, whichcorrespondstotheperiodofstimulationpreviouslyappliedforS1–S3(1h). Thisresponseimpliesthattheorganism hadstoredamemoryoftheperiodicity somewhereinitsbodythatwaslaterretrieved.Thistypeofbehaviourcanbe seenasaprimitiveformofrecall. ThewhitebarsandcirclesinFig. 1.5 indicate theresponsesofagroupoforganismsthatshowedanticipatorybehaviouratC1, whereastheblackbarsandcirclesrepresentthegroupthatfailedtodisplaythis behaviour.Recallbehaviourwasobservedevenforthegroupthatfailedanticipatory behaviour,althoughtheresponsewasslightlyweakerthanthatofthesuccessful group.Thus,recallwasnotrestrictedto individualsthatsucceededinshowing anticipatorybehaviour,whichimpliesthatstoringamemoryisaprocessthatoccurs

Fig.1.5 RecallbehaviourinresponsetostimulationS4appliedaftertheanticipatoryresponsehas disappeared,studiedbymeasuringthestatisticaloccurrenceofslowdown(a)andaveragedspeed (b)over40repeats.Thecriterionforspontaneousslowdownwasacceleration 0.2mm/(10min). Thewetweightoftheorganismwas15mg.ThedataofthesuccessofSPSshowninFig. 1.5b werethesameasthosepreviouslypublished(Saigusaetal. 2008).Thenumberofrepeatswas40, andthisnumberofrepeatswasthesumofthenewdataandthepreviousexperiments(Saigusaet al. 2008).Mean ˙ standarderrorofmean.Statisticalsignificanceofdifferencewastestedby t test. The p valuewasnotobservedtobelessthan0.01betweenthesuccessandthefailuregroupsatthe timepointsofC1,C2–C5,andC6

inthebodyofbothgroups.Despitefluctuationsinthetimesatwhichanticipation andrecalltookplace,itisclearthat Physarum isabletostoremeaningful informationintheformoftimememory.

ModulationofRhythmicContractionDuringSpontaneousSlowdown Figure 1.6 showsatypicaltimecourseoftherhythmiccontractionthatoccurredwhen theorganismshowedanticipatorybehaviour.Theplasmodiumusuallydisplays periodiccyclesofcontractionandrelaxationovertheentirebodywithanaverage period £ ofapproximately1min,asshownbythespatiotemporalplotofthe oscillationperiodinFig. 1.6a.Theoscillationperiodoftheentirebodybecame 70slongerwhenstimulationwasappliedatS1,S2,andS3.Duringthespontaneous slowdownoflocomotionspeedatC1,sloweroscillationswereobserved(£ 90s), butthisincreaseinperiodwassmallerthanthatatS1,S2,andS3.Figure 1.6b,c showsthetimecoursesoftheoscillationperiod,averagedovertheentirebody,and ofthelocomotionspeed,respectively.Anincreaseintheperiodofthecontraction rhythmwasclearlyobservedatC1inFig. 1.6b.Aminimuminthetimecourseof thespeedwasalsoobservedatC1(Fig. 1.6c),asoccurredatS1,S2,andS3.Thatis,

Fig.1.6 Modulationofcellularrhythminresponsetoperiodicstimulation.(a)Periodofrhythmic contractionasafunctionoftime.(b)Timecourseofcontractionperiod,averagedoverfrontalpart oforganism(1cmfromextendingtip).(c)Speedoflocomotionwithrespecttotime:atypical responseinallthreerepeats.Bodyweightinitiallyinoculatedwas10–19mg

therhythmiccontractionsloweddownwheneverthelocomotionspeeddecreased, whetherinducedbyexternalstimulationorasaresultofspontaneousanticipatory behaviour.Thisresultimpliesthattheelementaryprocessofanticipatoryresponse involvesnotonlytheoverallbehaviouroflocomotionbutalsothelocalkineticsof biochemicaloscillatoryreactions.Figure 1.7 showsthechangesinoscillationperiod (Fig. 1.7a)andlocomotionspeed(Fig. 1.7b)associatedwiththerecallbehaviourat C6(theexperimentalconditionswerethesameasinFig. 1.5.).Inthetimecourse ofthecontractionperiod,amaximumsimilartothatobservedfortheanticipatory responsewasdisplayedatC6.Thetimecourseofthelocomotionspeedshowed amaximumbetweenS4andC6andaminimumatthebeginningofC6.That is,aslowdowninbothcontractionrhythm(maximumofperiod)andlocomotion (minimumofspeed)occurredduringtherecallbehaviouraroundC6.Inthissense, therecallbehaviourwassimilartoboththe anticipatorybehaviourandtheslowdown inducedbyexternalstimulation.

C5 S4

Fig.1.7 Modulationofcontractionrhythmduringrecallresponse.(a)Timecourseofcontraction periodafterstimulationS4.(b)Timecourseoflocomotionspeed:atypicalresponseinallthree repeats.Bodyweightinitiallyinoculatedwas10–19mg

1.2.4Discussion

FurtherExaminationofDataandConfirmationofDependencyofApplied frequency Althoughthepreviouspapershowsjustthefindingsoftheanticipatory behaviourand,inparticular,informationondependencyofappliedperiodicityis verylimited,thecurrentpapershowsamoreconsistentanalysisofdata,inwhich notonlythenewdatabutalsothepreviousdataoftheexperimentareincluded.

Figure 1.4 givesanoverallpictureofanticipatoryresponseintheparameterspace thatwasspannedbytheappliedperiodicityandtime.Theanticipatoryresponse wasobservedtoshowadeviationoftimetospontaneousslowdownaroundthe correcttimepointsC1andC2,buttheanticipatoryresponsewasclearlyobserved aroundC1whenwelookedthroughaseriesofperiodicity.Thetimedeviationof SPSincreasedasthetimeprogressedfromC1toC3.AroundC3,theanticipatory responsewasnolongerobserved.Whenweconsiderjustificationforthephysical mechanismproposedfortheanticipatorybehaviour,statisticaldistributionofthe deviationmaygiveushelpfulinformation.

AsshowninFig. 1.5a,theplasmodiathatfailedthefirstanticipation(0%atC1) wereabletosucceedinthesecondandthirdanticipation(approximately30–40% atC2andC3).Thisisremarkable.Itisinterestingtocheckwhetherthisresponseis reproducedbythepreviouslyproposedmathematicalmodel.

SizeEffect Ingeneral,itisknownthatthelargerplasmodiumismoreresistive againstsuddenchangesinenvironmentalconditionssuchastemperatureand humidity.Forinstance,althoughonelargeorganismcansurviveagainstadrop inhumidityalthoughsomepartofthelargebodyisnecrotic,amuchsmaller onecannotsurviveagainstthesamedropinhumidity.Thisdifferencemaybe becauselossofwatervapourfromthesurfaceofthebodyisrelativelyhigherin smallerorganisms:thesurface–volumeratioincreasesasthebodysizedecreases, inprinciple.So,weexpectthatsmallerorganismstendtobemoresensitivetothe periodicenvironmentalchange.Ifbodysize,however,issmallerthanthecritical size,theorganismcandieortrytotransformtoarestingstagesuchasthespore andsclerotium.Theanticipatorybehavioursobservedhereobeyabalancebetween maintenanceofvegetativestage(plasmodium)andmorphologicaltransformationto restingstage(sporeandsclerotium).Itisreasonablethatasmallerplasmodiumis sensitivetotheperiodicchangesinhumidityandtemperatureasfacingtohigher riskofsurvival.

InhomogeneityofResponseinaWholeBody Wediscusstheresultthatthe anticipatoryresponsewasnothomogeneousinthewholebodybutdifferedfrom parttopart:onepartmightbesuccessfulwhileanotherpartisnot.Accordingto theimplicationofthepreviouslypublishedmodelfortheanticipatoryresponsein Physarum (Saigusaetal. 2008),thecapacityisbasedonthechemicalkineticsof acomplicatednetworkofbiochemicalreactions.Itisreasonablethatbiochemical reactionsareverysimilaroverthebodybutstatesofreactiondonotalways synchronizebecausechemicaldiffusionandprotoplasmicstreamingmaynotbe alwayssufficientformaintainingperfectsynchronizationthroughoutthebody.In fact,somechemicalssuchasATP,Ca2C ,andNAD(P)Hshowinhomogeneous distributioninthebodyandmoreoversuchinhomogeneityisactivelyrelatedtothe developmentofamoeboidbehaviourin Physarum (NakamuraandKamiya 1985; Uedaetal. 1990;Ueda 1993;Yoshiyamaetal. 2010).So,spatialdifferencesof anticipatoryresponsemayresultfromtheinhomogeneityofdynamicstatesof reactionkinetics.

RecallwithNoAnticipation Intheresultsshowninthispaper,theplasmodium thatfailedtheanticipatoryresponsesometimessucceededintherecallbehaviour. Accordingtothemathematicalmodelpreviouslyproposed(Saigusaetal. 2008), thecoreprocessinkineticmotionofbiochemicalreactionsintheplasmodiumis thattwokindsofphasesynchronizationtakeplace:synchronization(orformation ofphasecluster,inotherwords)betweenbiochemicaloscillatorsthathavethesame naturalfrequency(thesamebiochemicalspecies,forinstance),andsynchronization betweenthethesephaseclustersthathaveaslightlydifferentnaturalfrequency.The secondsynchronizationisrelatedtorecallbehaviourwhereasthefirstoneisrelated tostoringthememoryofperiodicity.Asthesetwosynchronizationphenomena canbeseparable,wemayexpectthatrecallispossiblewithoutanticipation.Itis interestingthatthispossibilitycouldbeexaminedintheconventionalmathematical modelforanticipatoryandrecallbehavioursinthefuture.

Theplasmodiathatfailedthefirstanticipation(0%atC1;Fig. 1.5a)wereableto succeedthesecondandthirdanticipation(approximately30–40%atC2andC3). Thisisremarkable.Itisinterestingtocheckwhetherthisresponseisreproducedby thepreviouslyproposedmathematicalmodel.

EffectsonContractionRhythms Inthispaper,informationonintracellularstates wasshownforthefirsttime:modulationofintracellularrhythm.Thecontraction rhythm(thetypicalperiodis1–2min)wasmodulatedinresponsetotheenvironmentalchangesandthesamemodulationwasconfirmedinthespontaneous slowdownofanticipatoryandrecallbehaviours.Becausethisrhythmicitywasmuch fasterthanwehadconsideredinthemathematicalmodelling(appliedperiods were30–90min)inthepreviouspaper(Saigusaetal. 2008),theinformation fromthisresultdoesnothelptoexaminethemodeljustificationdirectly.At least,wecanextractthemessagethatoscillatoryactivityintheplasmodiumwas modulatedinrelationshiptodevelopmentofanticipatoryandrecallbehaviours. Furtherobservationandexaminationoffrequencymodulationataslowertimescale isinterestinginfuturestudiestoclarifythephysicalmechanismoftheanticipatory andrecallbehaviouratcellularlevel.

PossibleApproachtoPhysicalMechanism

Wehaveconfirmedtheprevious finding(Saigusaetal. 2008)byreexaminingnotonlynewdatabutalsotheprevious datatogether. Physarum exhibitsanticipatoryandrecallbehaviourinresponseto periodicchangesinenvironmentalconditions.Humanshaveasimilarcapacity. Ourstudyimpliesthatthistypeofcapacityisnotspecifictoasinglespecies butrathermaybefoundinmultiplespecies distributedoverawiderangeofthe phylogenetictree.Therefore,theunderlyingmechanismshouldbeconsideredas acommonprocess.Oneapproachtostudyingsuchamechanismistosearchfor specificgenesandproteinsthatareinvolved,butanalternativeapproachisthe modellingofphysicaldynamics.Accordingtothelatter,asimpleandgeneralmodel canbeproposed:anticipatoryandrecallbehaviourisreproducedbythecollective motionofindependentoscillatorswithawiderangeofnaturalfrequencies.Thisisa possiblemodelfortheanticipatorybehaviour,butanothersetofmodelequations isalsoproposed(Tachikawa 2010).Althoughthediscussionsonthepossible physicalmechanismarestillongoing,itisremarkablethathighercapacitiessuch asanticipationandrecallarecreatedbythesimpleandgeneralmodelofdifferential equations.Thestudyofhowprotozoaanticipateperiodiceventshintsattheorigin oftimememoryfromanevolutionarypointofview.

EvaluationMethodforMemoryCapacityforComplexityofTimeSequence

Inthisreport,thestimulationwasappliedinregularlyperiodicfashion.Thetime sequenceofthestimulationcouldbemademorecomplex.Forinstance,possible sequencesare(1)alternativechangesinthestimulationmagnitude,strongandweak, overaregularperiod;(2)double-frequencystimulationssuchasalternatinglongand shortstimulationperiods;and(3)achaoticsequenceofstimulations.Accordingto theideaspresentedhere,wemaybeabletodesignastandardtesttoassessthe capacityoftimememorythroughoutthephylogenetictreethatwillbeperformedin thefuture.

1.3ElectricControlofBehaviourin Paramecium

Paramecium isagenusofpopularunicellularciliatedprotozoathatyoucanfind easilyinthepondnearyouroffice.Theiraveragelengthandwidthareabout200 m and60 m,respectively.Althoughtheyhaveasimplerbodyplanthanours,their behavioursaresorichthatwecanbegluedtothemicroscopeforlongmoments. Theyhavemanycilia(about10,000)ontheirbodysurfaces,andtheyswimby ciliarybeatingthatisspatiotemporally coordinatedthroughtheentirebodysothat theyformametachronalwave.

Theycanchangetheirswimmingdirectionsbychangingthedirectionsofthe effectivestrokeofciliarybeating.Ordinarily,inauniformenvironment,theyswim forwards.However,whentheyencounteranobstacle,theyswimbackwardsfora whilebyreversingthedirectionoftheeffectivestrokeofciliarybeating(reversalof ciliarybeating),andafterswingingtheiranteriorend,theybegintoswimforward inanewdirection.Thisbehaviouriscalledavoidingreaction(Jennings 1906).

Therelationshipsbetweenthebehaviourandelectrophysiologicalpropertyof Paramecium hasbeenintensivelystudiedformorethan50years.Duringnormal forwardswimming,theyhaveaninternallynegativerestingpotentialthatisprovidedbytheintracellularhighKC andlowCa2C concentrations.Itwasknownthat theincreaseinintraciliaryconcentrationoffreecalciumion([Ca2C ]i )isnecessary forthereversalofciliarybeating,anditisproducedbydepolarizationofthecellular membrane(NaitohandEckert 1969;NaitohandKaneko 1972).

Theappearanceoftheavoidingreactionbehaviourisexplainedasfollows:When theorganismcollidesaobstacleatthefrontend,themechanosensitiveCa2C channel opens.Theresultingdepolarizationthatoccurredaroundthereceptorsspreads immediatelytotheentire bodyincludingcilia.Thedepolarizationoftheciliary membraneopensthevoltage-sensitiveCa2C channelsonthemembranesothatCa2C flowsintotheciliafromtheoutsideofthebody.Theincreaseof[Ca2C ]i provides thereversalofciliarybeatingsothattheorganismbeginstoswimbackwards.The ciliaryreversaliscontinuedduring[Ca2C ]i overacertaincritical concentration (NaitohandKaneko 1972).Therelaxationofthe[Ca2C ]i leadsittoresumethe forwardswimming.Thesedatashowsthat anexcitablecellularmembraneinthe protozoanactsasareceptoroftheexternalstimulusandatransmitterbetween thereceptorandtheeffector,whereasthoseareenactedbyneuralsystemsin eumetazoans,includinghumanbeings(Fig. 1.8).

Whatkindsofadaptabilitycanbeshownby Paramecium?Iftheyexist,we canexpecttounderstandthemfromthepointofviewofthemembranepotential phenomenaandtheirsucceedingbiochemicalreaction.Actually,variousbehaviours inProtozoahavebeenreportedsince100yearsago(Jennings 1906;Smith 1908; Bramstedt 1935;Applewhilte 1979).Smith(Smith 1908)foundanovelbehaviour of Paramecium inadead-endedcapillarytube.Inthisexperiment,theorganismwas putintoanarrowtubeofwhichthewidthwassmallerthanitslength,enoughnot tobeabletoturnbytheavoidingreaction.Inthebeginning,theorganismswims forwardtowardstheclosedend.Aftercollidingwiththetubeendatitsfrontpart,

Fig.1.8 Signaltransmissionbyelectrogenesisin(1)Eumetazoaand(2)Protozoa

itswimsbackwardaboutitsownlengthandresumesswimmingforwardly;thisis apartoftheordinaryavoidancereactionandwasrepeatedatleastadozentimes. Finally,aftersomestruggling,theorganismsucceededtochangeitsbodydirection bybendingthebodyintoaU-shape.

Howdotheybehavewhentheyencounteramoredifficultsituation?Recently wereportedanothernovelbehaviorof Paramecium inadead-endedcapillarytube (Kunitaetal. 2014).Weusedanarrowertubesothat Paramecium cannotchange itsbodydirectionbybendingitsbody.Thetypicalbehaviourisasfollows:After theorganismwasputintothetube,asinSmith’sexperiment,theordinaryavoiding reactionappearedattheclosedend.Thatis,theorganismapproachedaforwardend andrepeatedback-and-forthswimmingwith ashortdistance(<0.5mm).Afterthat, forabout1min,thedistanceofbackwardswimminggraduallyincreasedandfinally reachedamaximumdistance(3–4mm).Itcontinuedthelong-distancebackward swimmingforafewminutes.Wecalledtheemergentlong-distancebackward swimming‘long-termbackwardswimming(LBS),’whereasthatintheordinary avoidingreactionisshort-termbackwardswimming(SBS).

1.3.1ParameciumModel

WhatisaunderlyingmechanismoftheemergenceofLBS?Naitoh(Naitoh 1990) hasreportedthatalong-termapplicationofoutwardcurrenttotheparamecium providedlong-lastingbackwardbeatingofciliaevenaftertheearlyinwardCa2C currentdisappeared.Naitohsuggestedthelong-lastingbackwardswimmingis

causedbyasmall-amplitudelong-lastinginwardCa2C currentthatflowsintothe sameCa2C channelfortheearlyinwardCa2C current.Basedonsuchprevious studies,weexploiteda Paramecium modelusingaconductance-basedmodeland attempttodemonstratetheLBS.

CiliaryMembrane Letusbeginwithmodellingoftheciliarymembranebasedon aconductance-basedmodel.Thetotalciliarymembranecurrent(IM )isthesumof thecapacitive(Ic )andtheioniccurrents(Ii ),andso:

where E isthepotentialdifferencebetweenthebetweentheoutsideandtheinside ofthemembraneandtheoutwardcurrentisdefinedaspositivecurrent.The restingequilibriumpotential(Er )isrealizedduringordinaryforwardswimming. Forsimplicityofnotation,weuseV D E Er insteadof E inthefollowing.Itis knownthatthevoltage-sensitiveCa2C channelandalsothevoltage-sensitiveKC channelarelocatedprimarilyintheciliarymembranewhereastheyarenotfound inthesomaticmembrane(Dunlap 1977;MachemerandOgura 1979;Eckertand Brehm 1979).Then,theioniccurrentIi isgivenby

where ICa and IK areCa2C andKC currents,respectively; IL isarelativelysmall voltage-independentconductanceofundeterminedions;and VCa , VK ,and VL are theequilibriumpotentialfortherespectiveions.Weusethefollowingconductance formula,whichwasproposedbyNaitoh(Naitoh 1979;NaitohandSugino 1984).

Here,eachgatevariable m, h,or n 2 [0,1]developsby dz=dt D ˛z .V /.1 z/ ˇz .V /z,where ˛ z (V ), ˇ z (V )arethepairofvoltage-dependentreactionrates(z D m, h,n)thatweredeterminedbyreferenceto themeasurementdataavailablefrom (Hiranoetal. 2005).1 Inthefollowing,time,potential,currentdensity,conductance,

1 Theexpressionofthefunctionsforthevoltage-dependentreactionrates(˛ , ˇ ) weredeterminedbyreferencetothemeasurementdataavailablefrom(Hiranoetal. 2005)asfollows: ’m (V ) D 0.39(46.40 V )/(exp(0.039(46.40 V )) 1), ˇ m (V ) D 0.65 exp( V /15), ˛ h (V ) D 0.05exp( V /50), ˇ h (V ) D 1.0(exp(0.032(V 39.29)) C 1), ˛ n (V ) D 0.038(58.58 V )/(exp((58.58 V )/8.17) 1), ˇ n (V ) D 0.10exp( V /68).However the ˛ h wasdeterminedadhoc,becauseitsdatawerenotavailable.Theconstantvaluesinthis paperweresetasfollows(Naitoh 1990;Hiranoetal. 2005). Er D 30, ECa DC116, EK D 41,

capacityandconcentrationaregiveninms,mV, A/cm2 ,mS/cm2 , F/cm2 ,and M,respectively.

MechanicalStimulationattheDead-EndandDepolarization Amechanical stimulationatthecapillarydeadendinducesadepolarizingreceptorpotential fromthemechano-sensitivechannelsdistributedontheanteriorpartofthesomatic membrane.Thispotentialchangeinthelocalmembraneareaspreadstotheentire membranealmostinstantaneously(Dunlap 1977)asaresultofthesuccessive inductionoftheoutwardcapacitivecurrentpassingthroughthenon-depolarized adjacentmembrane.Inourmodel,theresultantcurrentontheciliarymembraneis implementedas IM D Imech (>0)in(1)whentheorganismisatthecapillarydeadend (x D 0);otherwise, IM D 0.

RelationshipBetweenIntraciliaryCa2C ConcentrationandSwimmingVelocity Theswimmingvelocity(v)againsttheintraciliaryfreeCa2C concentration ([Ca2C ]i )hasbeenobtainedinchemicallyskinnedcells(NaitohandKaneko 1972), where[Ca2C ]i duringnormalforwardswimmingis10 2 Mandthesignofthe swimmingvelocityswitchisnear1 M.Figure 1.9b showsthe[Ca2C ]i versus v graphthatisusedinthesimulationand wasdeterminedbyreferencetothe experimentaldatain(NaitohandKaneko 1972),butthevelocity(v)wasrescaled byafactoroftenbecausethevelocityofthenormalforward-swimmingspecimen isexpectedtobe1–2mm/s(Kunitaetal. 2014).

EstimationofIntraciliaryCa2C Concentration Incontrasttothemembrane potential,calciumionscannottraverse betweencellularbodyandciliabecause ofcytoplasmbufferaction(Naitoh 1990).ExtraciliaryCa2C passesonlythrough theciliarymembrane.Ontheotherhand,theCa2C areexportedtotheoutside bycalciumpumpsontheciliarymembrane.So,weassumedthat[Ca2C ]i is approximatelydeterminedbythecontributionsofCa2C channelsandCa2C pumps ontheciliarymembraneandissimplyestimatedbythefollowingequation:

whereFisFaradayconstant[C/mol], sv isaconstantproportionaltothesurface-tovolumeratioofthecilium,and p [ms 1 ]isarateconstantdependingontheCa2C pumpperformance. Km [ M]istheconcentrationatwhichthepumpoperatesat halfitsmaximumrate,and I 0 Ca and Ca2C 0 i arethesmallconstantsofCai Ca2C currentand[Ca2C ]i duringtheordinaryforwardswimming,respectively.

Fig.1.9 Ademonstrationoftheemergentbehaviour(LBS)bythe Paramecium modelinthe narrowdead-endcapillarytube.(a)Experimentalsetting.The Paramecium isconfinedinthe glasscapillarytube(0.08mmdiameter,40–50mmlength)ofwhichtheendwasclosedwith mineraloil(Kunitaetal. 2014).(b)IntraciliaryCa2C concentrationversusswimmingvelocity. v D v 1 C (v1 v 1 )/(1 C b[Ca] a )(mm/s)where v 1 D 1.40, v1 D i 0.60, a D 2.0, b D 2.91 10 7 .(c)Timecoursesofthepositionof Paramecium (upperpanel),membranepotential(middlepanel),andintraciliaryCa2C consecration.The verticallines throughthethreepanels indicatethetimingswhentheorganismreachedthedeadend(x D 0)withforwardswimming. Imech D 5, Km D 1 102 , pu D 1.0 10 2 ,and sv D 10 area/vol,wherearea/vol D 2.0 108 (cm2 /l)isthesurface:volumeratioofacilium(Machemer 1974).(d)Abifurcationdiagramof thebackwarddistance(dLBS )duringtheLBSperioddependingonthesensitivitytomechanical stimulation(Imech ).(e)Timecoursesofthepositionofthe Paramecium modelwith Imech D 6.6 (upperpanel)and7.7(lowerpanel).Inallsimulations,thetimeconstantoftheslow-inactivated Ca2C channelwassettobe2000timesthatoftheordinarychannel

SlowCa2C CurrentInducedbyRepetitiveStimulation Thesmall-amplitude, long-lastinginwardCa2C currentsmentionedbyNaitoh(1990)areassumedtobe recruitedbyrepetitivecollisionsattheforwardendofthecapillarytube.Thisis implementedinourmodelinthatanordinaryCa2C channelontheciliarymembrane ismodifiedtoaslowinactivatedonewithaprobability ı peverytimeanaction potentialhappens,althoughitbecomesnormalagainexponentiallyovertime.2

SimulationResults Figure 1.9c showsanexampleofthetimecourseofthe positionandtheciliaryelectrophysiologicalstatesofthe Paramecium model.The organismshowedLBSafterSBS(t <50s)viaagradualincreaseofthebackward swimmingdistance(upperpanelofFig. 1.9c).TheshiftfromSBStoLBSwas causedbytheinteractionbetweentheorganismandenvironmentviathecollisioninducedrecruitmentoftheslow-inactivatedciliaryCa2C channel.Becausethe temporalpositionandtheelectrochemicalstatesoftheorganismaredetermined byboththeinternaldynamics(Eqs. 1.1–1.6)andthehistoryofthecollisionwith thetubeend,themodelbehaviourcanbemorediversethanthatderivedfrom onlytheinternaldynamics.Ourmodelincludesseveralparametersofwhichvalues mayvarythroughthespecimenorenvironmentaluncertainfactors.Imech isone ofsuchparametersanditrelatestothesensitivitytomechanicalstimulations.

Figure 1.9d showsdependenceofbackwarddistancesafteremergenceofLBS on Imech .Asanincreaseof Imech ,variousqualitativechangesoccurred,including doublingofthebackwarddistances,suddenoccurrenceofanewlongbackward distance,interveningofSBS-likebehaviour,andsoon.Suchabifurcationdiagram suggeststhebehaviourduringLBScanvaryfromsimpletocomplexandviceversa dependentonspecimensandenvironmentaldetails.Actually,severalvariantsof theLBSbehaviourwereobservedinourexperiments.However,thequantitative analysisofsuchaspectsarestillnotdeveloped.Furtherinvestigationisleftforfuture studies.

1.4ComparativeRemarksin Single-CelledOrganisms andHigherOrganisms

Althoughthecapacityofmemoryandlearningisgenerallyassumedtobelimited tohigherorganisms,anumberofstudieshavesuggestedthattheseattributescan alsobedisplayedbyunicellularorganisms(Bray 2009;Eisenstein 1975;Corning andVonBurg 1973;Reidetal. 2012, 2013;HinkleandWood 1994)aswellasby nonlivingsystemssuchasspinechoandelectroniccircuits(Pershinetal. 2009;

2 Inthesimulation,the ı passumedtobeproportionaltons (n ns )/n2 sothatns growsandsaturates inasigmoidalmanner,wherenisthetotalnumberoftheCa2C channelsandns isthenumberofthe modifiedchannels.Theupdateequationforp D ns /nisgivenasp(t) D (p(ti ) C kp p(ti )(1 p(ti ))) exp( (t ti )/ p ) C p" ,whereti isthemostrecentcollisiontime,0<kp 1isagrowthrate, p is arelaxationtimeconstant,andp" isasufficientlysmallpositiveconstant.

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Title: The butterfly guide

A pocket manual for the ready identification of the commoner species found in the United States and Canada

Author: W. J. Holland

Release date: May 3, 2024 [eBook #73524]

Language: English

Original publication: United States: Doubleday, Page & Company, 1915

Credits: Lisa Corcoran, Stephen Hutcheson, Chris Curnow, A Marshall and the Online Distributed Proofreading Team at https://www.pgdp.net *** START OF THE PROJECT GUTENBERG EBOOK THE BUTTERFLY GUIDE ***

TRANSCRIBER’S NOTE

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Some minor changes to the text are noted at the end of the book.

THE BUTTERFLY GUIDE

THE BUTTERFLY GUIDE

A POCKET MANUAL FOR THE READY IDENTIFICATION OF THE COMMONER SPECIES FOUND IN THE UNITED STATES AND CANADA

Director of the Carnegie Museum Author of “The Butterfly Book,” “The Moth Book,” etc. With 295 Colored Figures Representing 255 Species and Varieties

Copyright, 1915, by

D, P C

All rights reserved, including that of translation into foreign languages, including the Scandinavian

To the BOY SCOUTS OF AMERICA

I dedicate this Book

The Author

PREFACE

Recent advances in the arts make it possible to illustrate books at much less cost than formerly. An important invention is the process of printing in three colors from half-tone plates. The author of this manual was one of the first to use this process in illustrating a work upon the lepidoptera. When “The Butterfly Book” appeared he received letters from many scientific friends expressing their wonder Among those who wrote to him was Dr. Samuel Hubbard Scudder, the Nestor among American lepidopterists, who has since passed away. He said: “I am simply astonished at the fidelity to nature displayed by the plates in your book, and at the low price at which the new process permits it to be sold.”

That “The Butterfly Book” met a real need is shown by the fact that more than thirty thousand copies have already found purchasers. It is, however, a biggish book. The publishers, Messrs. Doubleday, Page & Co., have asked me to get up a little pocket manual of the butterflies, similar in form to the “Flower Guide,” which has been most cordially received by the public. I have therefore prepared the following pages, to which in the gracious phrase of our forefathers I now “invite the attention of the gentle reader.”

There are more than six hundred species of butterflies found in North America, north of the Gulf of Mexico and the Rio Grande. Most of these are figured in “The Butterfly Book.” In this manual two hundred and fifty-five species and varieties are depicted in their natural colors. They are mainly the commoner forms, which occur in the more densely inhabited parts of the United States and Canada. I have, however, included numerous forms from the Southern States, and not a few of the more showy species from the Pacific Coast.

In some cases only half of the insect is shown. “Half a loaf is better than no bread.” In some cases only one side of the wings is delineated. Usually this is sufficient for identification. The inhabitants

of this earth have never seen but one side of the moon, but they know it when they see it, unless they be like the tipsy pair, one of whom said to the other, who was leaning against a lamp post, “Friend, is that the moon, or a lamp?” and who received the reply: “Don’t ask me, I’m a stranger myself in these parts.” By showing only one half, or one side, of a species I have been able to illustrate many more than I could otherwise have done.

The figures of some of the larger species have been slightly reduced to accommodate them to the page, but as the natural size is always given in the description the student need not be perplexed.

The author hopes that his readers will have as much pleasure in studying the winged fairies of the woods and the fields as he has had in preparing this small pocket guide for their assistance.

INTRODUCTORY

THE PLACE OF BUTTERFLIES IN THE ANIMAL KINGDOM

The Animal Kingdom is divided into various subkingdoms. One of these is the subkingdom of the Arthropoda. This word is derived from the Greek nouns ἄρθρον (arthron) meaning joint, and πούς (pous) meaning foot. The Arthropoda are animals the bodies of which are made up of a series of rings or segments jointed together, and the other organs of which are likewise composed of tubular bodies similarly united. All arthropods are invertebrates; that is to say, they do not have backbones and internal skeletons, such as are possessed by fishes, reptiles, birds, and mammals, including man. Vertebrate animals have endoskeletons, “inside skeletons.” In a ham, for instance, the bone is internal to the muscular parts, or meat, and lies near the middle. The muscles of a man clothe his bones. In the arthropods, on the contrary, the hard parts clothe the muscles. Arthropods are therefore said to have exoskeletons, “outside skeletons.” The body, the legs, and other organs of an insect or a crab consist of a series of hollow tubes held together by flexible skin at the points of union, and controlled in their movements by muscles which pull from the inside. The meat of a lobster is inside of the shell, or exoskeleton, as everybody who has eaten a lobster knows. The arrangement is exactly the reverse of that which we find in the vertebrates.

EXPLANATION OF PLATE A

Fig. a. Magnified scales of butterflies. 1, ordinary scale of Papilio; 2, do. of Colias; 3 androconium, or scale from wing of male Neonympha eurytus; 4, do. of male Pieris oleracea; 5, do. of male Lycæna pseudargiolus (Figs. 1-2 after Verity; Figs. 3-5 after Scudder).

Fig. b. Patch of scales on wing of Pieris napi (after Verity).

Fig. c. Body of Anosia plexippus.

I. Head. 1, antenna; 2, eye; 3, proboscis; 4, palpus; cl. clypeus; o, occiput.

II. Thorax. 5, prothoracic leg; 6, mesothoracic leg; 7, metathoracic leg; e, e, e, episterna; c, c, c, coxæ; tr., tr., trochanters of last two legs; f, f, femora of do.; s, s, s, scuta of first, second, and third segments of thorax.

III. Abdomen. 1-9 segments; sp., sp., spiracles (after Burgess).

Fig. d. Head and legs of Œneis semidea, showing aborted front leg.

Fig. e. Palpus of Argynnis aphrodite.

Fig. f. Leg of Argynnis idalia. 1, coxa; 2, trochanter; 3, femur; 4, tibia; 5, tarsus.

Fig. g. Knobbed antenna of Argynnis idalia.

Fig. h. Clubbed antenna of Basilarchia astyanax.

Fig. i. Hooked antenna of Amblyscirtes vialis.

P A

The subkingdom of the Arthropoda is divided into six classes, one of which consists of the Insecta (insects). It is estimated that there are three and a half millions of species of insects upon the globe, not

to speak of the vast number of species which are now extinct, and known only by their fossil remains.

The Class Insecta is subdivided into many Orders To attempt even to briefly speak of all these orders would take more space than the publisher has allotted to the author, and it is enough to say that butterflies belong to the order Lepidoptera. The lepidoptera are divided into two Suborders: the Rhopalocera, or Butterflies, and the Heterocera, or Moths. Both are characterized by having scaly wings, hence the name, which is derived from the Greek words λεπὶς (lepis) meaning scale, and πτερὸν (pteron) meaning wing. Lepidoptera are “scale-winged insects.” Any one who has ever handled a butterfly or moth, must have noticed upon his fingers a dust-like substance, rubbed off from the wings of the captured insect. Upon examining this substance under a microscope it is seen to be composed of minute scales (see Plate A, Fig. a), and upon looking at the wing of a butterfly under a magnifying glass it is seen to be covered with such scales, arranged somewhat as the scales upon the sides of a fish, or as the shingles upon the roof of a house (see Plate A, Fig. b).

Butterflies are mainly diurnal in their habits, preferring the sunshine. Moths on the other hand are nocturnal, and fly in the dusk, or after dark. Butterflies are therefore often called diurnal lepidoptera, and moths are spoken of as nocturnal lepidoptera. There are, however, a few butterflies which fly at dusk, and there are many moths which are diurnal in their habits. Such moths are generally gay in color, and for the most part inhabit tropical countries, although we have a few such species in the United States. Ordinarily the best way to distinguish between butterflies and moths is by examining their antennæ, or “feelers,” as they are sometimes incorrectly called. In the case of butterflies the antennæ are threadlike, terminating in a small knob-like, or club-like enlargement. It is this fact which has led naturalists to call them Rhopalocera. The word is derived from the Greek nouns ῥώπαλον (rhopalon) meaning a club, and κέρας (keras) a horn. Butterflies are lepidoptera having at the end of their antennæ clubs, which are sometimes short, long, or hooked (see Plate A, Figs. g, h, i.) The forms assumed by the antennæ of moths are very various. The moths are therefore known

as Heterocera, the word being compounded from the Greek adjective ἕτερος ( all sorts) and the noun κέρας (keras) a horn. Moths are lepidoptera having all sorts of antennæ, except such as are club-shaped at their ends. However there is no rule without its exceptions, and there are a few rare moths in tropical lands which have club-shaped antennæ like butterflies, but none of these occur in the region with which this book deals.

THE ANATOMY OF BUTTERFLIES

The body of a butterfly consists of the head, the thorax, and the abdomen (see Plate A, Fig. c).

The head carries two relatively large eyes, one on either side. The eyes of insects are compound, and if examined under a microscope are seen to have a multitude of minute facets, which serve to gather the light from all directions, so that butterflies can look forward and backward, upward and downward, as well as outward, all at one time. Between the eyes on the upper part of the head arise the antennæ, of which we have already spoken. The precise function of these organs in insects has been the subject of much discussion. Supposed by some to be ears, by others to be the seat of the sense of smell, by others to combine within themselves these two senses, and by still others to represent a sense which is not possessed by vertebrate animals, their use in the life of insects is not yet clearly understood. The weight of evidence seems to be in favor of the view that they are organs of smell, and it is now quite firmly established by experiment that the organs of hearing in insects are represented by certain pores and openings on their legs. In front between the eyes and below the antennæ are two little organs, each composed of three joints, which are known as the labial palpi (see Plate A, Fig. e). Between these, coiled up like a watch-spring, is the proboscis, with which the butterfly sucks up the nectar from flowers or drinks water from moist places (see Plate A, Figs. c and d). We have not the space in this little manual to go more deeply into the anatomy of these organs, but enough has been said to enable the beginner to recognize the various parts. The student realizes that the head in

general supports the principal organs of sense and the proboscis, or mouth.

The thorax carries the organs of locomotion, which consist of four wings and six feet. The thorax is made up of three segments, or rings, the foremost of which is called the prothorax, the next the mesothorax, and the hindmost the metathorax. The subdivisions of the thorax are not easily distinguishable by examining the body of a butterfly even under a microscope, because the bodies of butterflies are generally heavily clothed with hairs and scales. In order to clearly make out the subdivisions, which we are considering, it is necessary to take a specimen and denude it of its scales and hairs, and even dissect it under a glass. The correctness of the foregoing statements then becomes apparent.

The legs of butterflies are arranged in three pairs, the foremost of which are known as prothoracic, being attached to the prothorax; the second pair are called mesothoracic, springing, as they do, from the middle segment of the thorax; and the last are styled metathoracic legs, rising from the hindmost segment of the chest (see Plate A, Fig. c). It should be noted here that in the great family of the Nymphalidæ, or “Brush-footed Butterflies,” in both sexes the anterior, or prothoracic pair of legs, are not fully developed, being aborted (see Plate A, Fig. d) and therefore do not serve for walking; and that in the families of the Erycinidæ, or “Metal-marks,” and the Lycænidæ, or “Blues and Coppers,” the females have six legs adapted to walking, while the males possess only four ambulatory legs, the front pair being in the latter sex aborted in these families, as in the Nymphalidæ. The legs of butterflies, like those of all other insects, consist of five parts (see Plate A, Fig. f) the first of which, nearest the body, is called the coxa, with which articulates a small ring-like piece, known as the trochanter. To the trochanter is attached the femur, and united with the latter, forming an angle with it, is the tibia. The last division of the leg is the tarsus, or foot, composed of a series of joints, to the last of which is attached a pair of claws, which in butterflies are generally rather minute, though in other orders of insects these claws are sometimes long and powerful, this being especially true of some beetles. The prothoracic

legs of the Nymphalidæ and of the males of the Erycinidæ and Lycænidæ have lost the use of the tarsus, only retaining it in feeble form, and the tibia has undergone modification. In many of the Nymphalidæ the tibia is densely clothed with long hairs, giving this part of the leg the appearance of a brush, whence the name “Brushfooted Butterflies” (see Plate A, Fig. d). The tibiæ are often armed with more or less strongly developed spines.

The most striking parts of butterflies are their wings, which in proportion to the size of their bodies are usually very large, and which are remarkable for the beauty of the colors and the markings which they display both on the upper and on the under side.

The wings consist of a framework of horny tubes which are in reality double, the inner tube being filled with air, the outer tube with blood. The blood of insects is not, like that of vertebrates, red in color. It is almost colorless, or at most slightly stained with yellow. The circulation of the blood in the outer wall of the wing-tubes takes place most freely during the brief period in which the insect is expanding its wings after emergence from the chrysalis, concerning which we shall have more to say elsewhere. After the wings of the butterfly have become fully expanded, the circulation of the blood in the wings ceases almost entirely. The horny tubes, which compose the framework of the wings of butterflies, support between them a delicate membrane, to which upon both the upper and lower sides are attached the scales. The two fore wings are more or less triangular in outline; the hind wings are also subtriangular, but are generally more or less rounded on the outer margin, and in numerous forms are provided with tails or tail-like prolongations.

Inasmuch as in describing butterflies authors generally devote a good deal of attention to the markings of the wings, it is important for the student to become acquainted with the terms employed in designating the different parts of the wings (see Plate B, Fig. 10). That part of the wing which is nearest to the thorax, is called the base; the middle third of the wing is known as the median or discal area; the outer third as the external or limbal area. The anterior margin of the wing is called the costal margin; the outer edge is styled the external margin; the inner edge is known as the inner

margin The tip of the front wing is called the apex, which may be rounded, acute, falcate (sickle-shaped), or square (see Plate B, Figs. 1-4). The angle formed by the outer margin of the front wing with the inner margin is commonly known as the outer angle. The corresponding angle on the hind wing is known as the anal angle, and the point of the hind wing, which corresponds with the tip or apex of the fore wing, is designated as the external angle. The margins of wings may have different styles of outline, and are spoken of as entire, crenulate, scalloped, waved, lobed, or tailed (see Plate B, Figs. 5-8).

A knowledge of the veins which form the framework of the wings is important, because authors have frequently established genera upon the basis of the wing structure. It is desirable on this account to understand the nomenclature which has been applied to the veins. This nomenclature is somewhat variant, different writers having employed different terms to designate the same vein. In what follows the writer has adopted the designations which are most current, and which are generally accepted by authors. The best understanding of this matter is to be derived from the attentive study of the diagrams given on Plate B, Figs. 9 and 10. The veins in both the fore and hind wings of butterflies may be divided into simple and compound veins. In the fore wing the simple veins are the costal, the radials, the submedian, and the internal; in the hind wing they are the costal, the subcostal, the radials, the submedian, and the internal. The costal vein in the hind wing is, however, generally provided near the base with a short ascending branch, which is known as the precostal vein. In addition to the simple veins there are in the fore wing two branching veins, one immediately following the costal, known as the subcostal, and the other preceding the submedian, known as the median. The branches of these compound veins are known as nervules. The median vein always has three nervules. The nervules of the subcostal veins branch upwardly and outwardly toward the costal margin and the apex of the fore wing. There are always from four to five subcostal nervules, variously arranged. In the hind wing the subcostal is simple. The median vein in the hind wing has three nervules, as in the fore wing. In both wings between the subcostal and the median veins toward the base is enclosed the cell, which

may be either closed or wholly or partially open at its outer extremity The veinlets which close the cell are known as the discocellular veins, of which there are normally three. From the point of union of these discocellular veins go forth the radials, known respectively as upper and lower, though the upper radial in many genera is emitted from the lower margin of the subcostal vein.

EXPLANATION OF PLATE B

Fig. 1. Angulated or acuminate apex of fore wing ( Grapta).

Fig. 2. Falcate apex of fore wing ( Pyrrhanæa).

Fig. 3. Square apex of fore wing ( Smyrna).

Fig. 4. Rounded apex of fore wing ( Euptoieta).

Fig. 5. Hind wing rounded at outer angle, twice-tailed ( Thecla).

Fig. 6. Hind wing crenulate, tailed, lobed at anal angle ( Papilio).

Fig. 7. Hind wing with outer margin entire ( Parnassius).

Fig. 8. Hind wing with outer margin waved ( Argynnis).

Fig. 9. Neuration of wings of Anosia plexippus.

Veins: C, costal; SC, subcostal; M, median; SM, submedian; I, internal; PC, precostal; UDC, upper discocellular; MDC, middle discocellular; LDC, lower discocellular; UR, upper radial; LR, lower radial.

Nervules:SC 1, 2, 3, 4, 5, first to fifth subcostal nervules; M 1, 2, 3, first to third median nervules.

Fig. 10. Wing of Papilio turnus, showing the names given to the different parts of the wings of butterflies.

P B

Butterflies generally hold their wings erect when they are at rest, with their upper surfaces facing each other, and only the under surfaces displaying their colors to the eye. In the genus Ageronia the insect prefers, like some moths, to settle upon the bark of trees, with the wings spread flat, and the head pointing downward. Many of the Hesperiidæ, or “Skippers,” have the habit when they are at rest of holding the fore wings folded together, while the hind wings are expanded horizontally. Many of the butterflies known as “Hairstreaks,” belonging to the genus Thecla and its allies, have the curious habit, when at rest upon the end of a twig or leaf, of moving their folded wings backward and forward, first on one side and then on the other, thus partially displaying with each movement the splendid blue surfaces of the upper side of the wings.

The abdomen of butterflies consists normally of nine segments (see Plate A, Fig. c). In most butterflies except the Ithomiids, the end of the abdomen does not extend beyond the anal angle of the hind wings. In the moths, on the other hand, there are multitudes of genera in which the extremity of the abdomen extends far beyond the hind margin of the posterior wings. This is particularly true of the hawk-moths. A minute examination of the abdomen of a butterfly

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