Chocolate brown Mayflys early

[FishingDaddy]

I used to remember seeing them at upper hall when i first started flyfishing, they were size 8 a chocolate brown with olive bands, chocolate wings, they were the first mayfly hatch to come off . Up north they were normally coming off memorial day weekend, the hatches were very profuse, I was at strafford bog this spring and the hatch was so thick, i should have saved a sample but didnt. I went to several local flyshops and they were rather clueless honestly. Does anyone have any idea what they are? thanks in advance.Oh yes they had three tails. two sets of wings,,,

[Troutaholic]

Those may be the chocolate covered drakes. I haven't experienced them, but did once enjoy a chocolate covered nymph.

[Oncorhynchus]

Isonychia?

[FishingDaddy]

Oncor, they do look like an ionychia except bigger.. they are most generally the first big hatch in may, isos are size 10?

[Oncorhynchus]

Yup...size 8 or 10.

Based on your description, the only mayfly species I can think of.

Bicolor in the spring and Sadleri in late summer. Typically when I see them the fish are taking the fast swimming nymphs or the emergers. Isonychia have a slightly purple or claret hue to them, but could look dark brown to your eye.

"Chocolate dun" is a common name given to a large mayfly more commonly called a "March Brown". But to me, march browns do not have chocolate wings or bodies.

[FishingDaddy]

I was thinking of this, and i remember seeing isos on the ct river below moore dam and they at least in my memory were smaller than the ones i saw early on ponds. Is it because as they hatch later in the season they are smaller, or just a diff subspecies? Thanks ono..