Inanycase,theattemptwasnotimitated;Ineversawanotherinstallationofthekind。Thereisonedefiniteconclusiontobedrawnfrommytwodiscoveries。Despitetheoddityoftheirstructure,whichisunparalleledamongthelocalflora,thetwoAmericanimportationsdidnotcompeltheinsecttogothroughanapprenticeshipofgropingandhesitation。Theonewhichfounditselfinthepresenceofthosenovelgrowths,andwhichwasperhapsthefirstofitsracetodoso,tookpossessionoftheirlobesandstalksjustasitwouldhavedoneofafamiliarsite。Fromthestart,thefleshyplantsfromtheNewWorldsuiteditaswellasthetrunkofanativetree。
TheMason—beeofthePebbles（Chalicodomaparietina）hasnoneofthiselasticityinthechoiceofasite。Inhercase,thesmoothstoneoftheparcheduplandsisthealmostinvariablefoundationofherstructures。Elsewhere,underalessclementsky,sheprefersthesupportofawall,whichprotectsthenestagainsttheprolongedsnows。Lastly,theMason—beeoftheShrubs（Chalicodomarufescens,PEREZ）fixesherballofclaytoatwigofanyligneousplant,fromthethyme,therock—roseandtheheathtotheoak,theelmandthepine。Thelistofthesitesthatsuitherwouldalmostformacompletecatalogueoftheligneousflora。
Thevarietyofplaceswhereintheinsectinstalsitself,soeloquentofthepartplayedbydiscernmentintheirselection,becomesstillmoreremarkablewhenitisaccompaniedbyacorrespondingvarietyinthearchitectureofthecells。ThisismoreparticularlythecasewiththeThree—hornedOsmia,who,assheusesclayeymaterialsveryeasilyaffectedbytherain,requires,likethePelopaeus,adryshelterforhercells,ashelterwhichshefindsready—madeandusesjustasitis,afterafewtouchesbywayofsweepingandcleansing。
ThehomeswhichIseeheradoptareespeciallytheshellsofSnailsthathavediedunderthestone—heapsandinthelow,unmortaredwallswhichsupportthecultivatedearthofthehillsinshelvesorterraces。TheuseofSnail—shellsisaccompaniedbythenolessactiveuseoftheoldcellsofboththeMason—beeoftheShedsandofcertainAnthophorae（A。pilipes,A。parietinaandA。personata）。
Wemustnotforgetthereed,whichishighlyappreciatedwhen——ararefind——itappearsundertherequisiteconditions。Initsnaturalstate,theplantwiththemightyhollowcylindersisofnopossibleusetotheOsmia,whoknowsnothingoftheartofperforatingawoodywall。Thegalleryofaninternodehastobewideopenbeforetheinsectcantakepossessionofit。Also,theclean—cutstumpmustbehorizontal,otherwisetherainwouldsoftenthefragileedificeofclayandsoonlayitlow;also,thestumpmustnotbelyingonthegroundandmustbekeptatsomedistancefromthedampnessofthesoil。Weseethereforethat,withouttheinterventionofman,involuntaryinthevastmajorityofcasesanddeliberateonlyontheexperimenter\'spart,theOsmiawouldhardlyeverfindareed—stumpsuitedtotheinstallationofherfamily。Itistoheracasualacquisition,ahomeunknowntoherracebeforementookitintotheirheadstocutreedsandmakethemintohurdlesfordryingfigsinthesun。