▁' elm - feed ing ▁group ' ▁( i . e . ▁moth s ▁whose ▁c ater p ill ars ▁only ▁feed ▁on ▁el m , ▁as ▁opposed ▁to ▁species ▁which ▁include ▁el m ▁in ▁their ▁di et ▁alongside ▁other ▁trees ) ▁are ▁the ▁cloud ed ▁mag pie , ▁the ▁dus ky - lem on ▁s allow , ▁and ▁the ▁less er - sp otted ▁and ▁white - sp otted ▁pin ions ▁– ▁but ▁whereas ▁all ▁of ▁these ▁species ▁can ▁feed ▁on ▁other ▁species ▁of ▁el m ▁( and ▁some ▁prefer ▁other ▁el ms ▁in ▁fact ), ▁Bl omer ' s ▁riv u let ▁appears ▁to ▁feed ▁on ▁w ych ▁el m ▁only . ▁ ▁The ▁distribution ▁of ▁Bl omer ' s ▁riv u let ▁matches ▁that ▁of ▁cal care ous ▁rocks , ▁mainly ▁in ▁wet ter ▁parts ▁of ▁the ▁country . ▁The ▁species ' ▁British ▁distribution ▁covers ▁two ▁main ▁areas ▁– ▁it ▁occurs ▁from ▁Dev on ▁through ▁Som erset , ▁W ilt shire ▁and ▁Br istol ▁to ▁South ▁Wales ▁and ▁the ▁south - west ▁Mid lands , ▁and ▁then ▁again ▁from ▁Derby shire ▁and ▁Not ting ham shire ▁through ▁York shire ▁to ▁County ▁Dur ham . ▁The ▁species ▁is ▁also ▁found ▁in ▁the ▁Ch il tern s , ▁North ▁Wales , ▁Lincoln shire ▁and ▁C umb ria . ▁However , ▁despite ▁having ▁quite ▁a ▁wide ▁ge ographical ▁spread , ▁the ▁moth ▁is ▁afford ed ▁a ▁status ▁of ▁Nation ally ▁Sc ar ce ▁( found ▁in ▁between ▁ 1 6 ▁and ▁ 1