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spent gnat

British  

noun

  1. an angler's name for the spinner of various mayflies, esp Ephemeris danica and E. vulgata, particularly when lying spent on the water surface after mating and egg-laying

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012