Complex sentence: Subimago and adult mayflies do not have functioning mouthparts and do not eat; the nymphs are mainly detritivores, feeding on organic particles that are moved into their burrows by the current of water caused by their constantly beating gills.
Split into simpler sentences: Subimago and adult mayflies do not have functioning mouthparts and do not eat. The nymphs are mainly detritivores, feeding on organic particles that are moved into their burrows by the current of water caused by their constantly beating gills.