screw-worm flies
...that the larvae of primary screw-worm flies feed on living tissue, but secondary screw-worm flies feed only on necrotic tissue?
...that the <a href="./Larva" id="mwBRE" rel="mw:WikiLink" title="Larva">larvae</a> of primary <b id="mwBRI"><a href="./Cochliomyia" id="mwBRM" rel="mw:WikiLink" title="Cochliomyia">screw-worm flies</a></b> feed on living tissue, but secondary screw-worm flies feed only on <a href="./Necrosis" id="mwBRQ" rel="mw:WikiLink" title="Necrosis">necrotic tissue</a>?