Definition of onion fly in English:

onion fly

noun

  • A small fly whose larvae are a pest of onions.

    • ‘It is the offspring of the onion fly, which sometimes flits about among the young onions at this season.’
    • ‘Similarly, the leek moth Acrolepiopsis assectella Zeller and the onion fly Delia antiqua Meigen are both attracted to their respective host plants by the flavour volatiles.’