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Introducing Tricorythodes The Trico Mayfly

By Jon Easdon, Director of Services


Ah, it’s that time of the year that all fly fishermen and women look forward to, the time when we squint our eyes and frantically throw size 26 dry flies to rising trout.  Trico’s (pronounced TREE-co, often mis pronounced TRY-co) are a small mayfly prevalent from about mid July to late September. Tricos are small, ranging from 3-7 millimeters in length. They become a staple on most every cold river in the west. On the South Platte they turn into the preferred meal of trout. These hatches can be so intense that their swarms look like smoke above the river. Because of the density of these hatches, they tend to lure all of the trout to feed on the top column of the river.

Tricos prefer cold water and silty, weedy areas in deeper pools on the river. The hatches are fairly predictable, with water and air temperature being the key to the hatch. The morning to mid-morning is typically the best time to witness these hatches. This is followed by the “spinner fall” and when most of the feeding occurs. The Tricos fall mercilessly to the surface of the river kicking off a massive feeding frenzy.


Fishing this hatch can be notoriously tough. The fish really seem to key in on certain sizes and life stages of the se mayflies. Over the years, on occasion I have personally thrown a bunch of different patterns trying to fool the fish to no avail. Studying the fish and their behavior is important in fishing this hatch. You can time the rises and time your presentation. Take the time to watch the fish before you go hucking flies at them.  A little patience can pay huge dividends.  I would also suggest having a second rod already rigged with a dry fly/ dry-dropper system. These hatches can turn on and off like the flick of a light switch.


Here are a few techniques and patterns I like to use during the Trico hatch.


Before the hatch really begins, a standard nymph rig with a black RS2 (size 22-24) will produce success. Green RS2s can also be electric as they signify the female trico. In my opinion, the RS2 should always be a staple in your fly box.  I also

like to fish small zebra midges during this stage. Black RS2 emergers or a black baetis emerger will signify the emergence stage. The density of these mayflies keeps these nymph patterns valid all day long as well.


During the spinner fall, I like to throw a combination of adult trico dry flies with a spent wing dropper. A very important thing to look for during the spinner fall are refusals to your flies. If you get a couple of refusals, change your flies!  It’s worth the time because when you do discover the hot pattern you can hook up on almost every cast.


I hope you can get out and enjoy one of the most fun dry events of the year; this hatch can be extremely rewarding when you take the time to figure it out.  Please stop by the shop and we would be happy to show you these patterns or just talk



Here are some of my go-to patterns for the Tricos:



* Black RS2 (size 22-24)

* RS2 emerger-whitleys sparkle wing (22-24)



juan's trickAdult dries

* Kleis’s lightswitch trico (24)

* Juan’s 180 degree trico (24)

* Spent wings-

* Engle’s drowned trico (22-24)

* Poly spinner (22-both male and female)

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