Massive mayfly at my house in seattle


We live about a half a mile from the lower Yakima River and find a couple of these on window screens around this time of the year. I wondered what they were as well. Never thought about Hex’s. Thx for the ID.


Active Member
East side here in Tac. I get them on my window screens and am over 2 miles away from the closest fresh water/ including the city water........


WFF Supporter
Found this outside my house on my way home today. It looks like a gigantic mayfly, but that is as much as I know. Any thoughts?


That's a Hexagenia Limbata spinner. Note the two tails.



Active Member
As you know, Hex Limbata nymphs are burrowers and line in sediment. They form the huge mayfly hatches that show up on weather radar when they emerge from the Mississippi River between Minnesota and Wisconsin.

Snow plows are used to clear the roads.

Incredible pictures illuminating what I mentioned earlier. The closest I ever came to seeing something like this was when, returning from a successful day fishing the Blitzen River, I ran into a midge hatch by Malheur Lake that covered my windshield. As I was driving into a setting sun, I was for all intents and purposes driving blind. When I pulled into a gas station in Burns and the attendant came out, I had to tell him I didn't need gas, just the ability to see the road! After that, I always kept a can of windshield bug removal spray and a roll of paper shop towels in the car.
A week later found me returning to my car to find a supermarket parking lot flock of starlings pecking sun-roasted midges off my front bumper.


Active Member
I’ve fished Hex hatches a few times on trout water in the east. The ones I’ve encountered have been a much lighter cream color, or near white. Cool to see the darker variation.


New Member
Found this outside my house on my way home today. It looks like a gigantic mayfly, but that is as much as I know. Any thoughts?

View attachment 247394

View attachment 247393
New to the forum here and a bit late on this topic but I find it interesting that these bugs show about the same time here on the east coast, I start seeing them around the 4th of July but ours are a bit smaller


  • D56DE874-E73B-456E-A812-25A177FB4FB4.jpeg
    787.1 KB · Views: 15
  • B7CD1C37-EE68-4207-A15B-914F93D52C0A.jpeg
    1.8 MB · Views: 15


WFF Moderator
Hi Drifly-

I believe them to female imago and male imago of either genus Hexagenia limbata or Hexagenia rigida, both of which are know to reside in many eastern costal states, and require microscopic examination of the male imaginal penes in order to distinguish from one another.


New Member
We’ll see these guys show up about a month earlier on the east coast, clearly rivals in size. Stanley


  • 3BC22D93-026C-4401-BC5D-A00436918E18.jpeg
    1 MB · Views: 4

Support WFF | Remove the Ads

Support WFF by upgrading your account. Site supporters benefits include no ads and access to some additional features, few now, more in the works. Info