Henry's Elfin
... that populations of the butterfly Henry's Elfin are growing in New England due to the introduction of buckthorn, which the butterflies now use as a host plant?
... that <a href="./Population" id="mwCCY" rel="mw:WikiLink" title="Population">populations</a> of the <a href="./Butterfly" id="mwCCc" rel="mw:WikiLink" title="Butterfly">butterfly</a> <b id="mwCCg"><a href="./Callophrys_henrici" id="mwCCk" rel="mw:WikiLink" title="Callophrys henrici">Henry's Elfin</a></b> are growing in <a href="./New_England" id="mwCCo" rel="mw:WikiLink" title="New England">New England</a> due to the introduction of <a href="./Rhamnus_cathartica" id="mwCCs" rel="mw:WikiLink" title="Rhamnus cathartica">buckthorn</a>, which the butterflies now use as a <a href="./Host_(biology)" id="mwCCw" rel="mw:WikiLink" title="Host (biology)">host</a> plant?