The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
The specific collection location data from this map were pulled from the Global Biodiversity Information Facility (GBIF) website under the Creative Commons license. Data there come from a variety of sources, some of which are populated by hobbyists. Both the precision of the location and accuracy of the identification could be low. This map is not an authoritative scientific source, nor an exhaustive list of everwhere this taxon is found, but it should be good enough for anglers. Click each marker on the map for more information about that report, including a link to more details on GBIF.