Answer: EARTHWORM

AnswerCrossword Clue
EARTHWORMCreature that Darwin identified as a benefit to agriculture
EARTHWORMBait shop critter
EARTHWORMNight crawler
EARTHWORMSoil aerator
EARTHWORMTreat for a trout
EARTHWORMFish food.
EARTHWORMBait.
EARTHWORMLive bait
EARTHWORMMole's prey
EARTHWORMAngler's bait, perhaps
earthwormthe common worm