Mayfly I.D

Hey guys, so in the spring every year on a coast range trout stream here in oregon, these larger brown mayflies hatch. the hatch lasts from opening day (end of april) until the end of may. These bugs are a brilliant rusty brown, with VERY long tails. the bugs are a full size 12 and can be seen all flying around in groups above the river. I was thinking march browns but to me they just seem too large, and the hatch lasts later.

here are the best 2 photos i have of the insect
Opening day 2014 033.jpg
Opening day 2014 031.jpg
Opening day 2014 031.jpg


Staff member

At what approximate elevation in the in the Oregon Cascades have you encountered this emergence?


The MBs I've seen on Mac and Willy start out quite large than as the year goes by, the bugs hatching are smaller but still the same critter. I know they're MBs because I frequently fish with an entomologist.

I've seen the larger MBs in the coast range and I'm pretty sure that's what is shown in the photos. At least, they sure look like the ones in The Valley. Dark back, light underbelly.

Roger, the altitude of the coastal rivers where Brandon is fishing is probably 400 feet at the most. I have found MBs later in the year at higher elevations in the Oregon Cascades. It seems the hatch starts at the lower elevation and then moves up over time. At least, that's been my experience.
gene you are spot on, the elevation being only between 2-500 ft depending on the section of river. this time of year i only see them high up in the river system but around opening day they are swarming the middle and lower portion of the river.


Latest posts