giant mayflies
... that the nymphs of giant mayflies feed on detritus in their mud burrows, but the adults do not feed at all?
... that the <a href="./Nymph_(biology)" id="mwApQ" rel="mw:WikiLink" title="Nymph (biology)">nymphs</a> of <b id="mwApU"><a href="./Hexagenia_limbata" id="mwApY" rel="mw:WikiLink" title="Hexagenia limbata">giant mayflies</a></b> feed on <a href="./Detritus" id="mwApc" rel="mw:WikiLink" title="Detritus">detritus</a> in their mud burrows, but the adults do not feed at all?