mayflies
... that on this evening a year ago, the swarm of mayflies near La Crosse, Wisconsin was so vast that it could be detected on weather radar?
... that on this evening a year ago, the swarm of <b id="mwAt0"><a href="./Hexagenia_bilineata" id="mwAt4" rel="mw:WikiLink" title="Hexagenia bilineata">mayflies</a></b> near <a href="./La_Crosse,_Wisconsin" id="mwAt8" rel="mw:WikiLink" title="La Crosse, Wisconsin">La Crosse, Wisconsin</a> was so vast that it could be detected on <a href="./Weather_radar" id="mwAuA" rel="mw:WikiLink" title="Weather radar">weather radar</a>?<!--Special occasion request for July 23-->