The Midgezilla Hatch

Recent guide reports indicate that the fishing on our local rivers has been off the charts with the annual “midgezillas” coming off in great numbers. With the best fishing to be midday during the warmest part of the day. The Lower Eagle and Roaring Fork have been the most consistent stretches of water.

What is the “Midgezilla”?

Here in the high country every spring the water temps begin to rise with the warm spring days and the infamous “midgezilla” begins to hatch in the local rivers like the Eagle River, Roaring Fork, and Lower Colorado River. The so called “midgezilla” is a slang term anglers used to generalize for larger sized midges, think of a size 16-18 midge pattern. Most often these bugs color variations are white, black, or olive. The midges are abnormally large and can often be mistaken for a blue winged olive or the nymphs can even be mistaken as caddis.

The midge insect is classified in the order Diptera, the two-winged flies. While a BWO is in the order Ephemeroptera, which have three tails in their winged-insect states. It is easiest to tell them apart by looking at the wings and the midges usually fly a little more clumsy than the Blue Winged Olives.

Fun Fact: The family of dipteran insects typically will make up at least half of the species of aquatic insects in any freshwater ecosystem. Midges might just be a snack for trout, but they are the most common and prevalent food source throughout the year.

How to Fish it?

Like all midge hatches, it is a buffet line for the hungry and eager trout, they consume as many of these low calorie snacks as possible. This means good action and opportunity for anglers. Look for the midges to be coming off the water in numbers and maybe even visible in back eddys or on the bank (on top of snow is a very easy way to identify midges). Once you have identified the hatch to be larger midges, assess the trout’s feeding behavior. Typically, when the hatch is on the trout are “sharking” around eating below the surface (You can see their dorsal fins at times as they eat the midge emergers). Since the fish are mainly eating below the surface the easiest and most effective technique to target these trout is with midge emergers on a shallow nymphing rig.


A nine foot 5x leader with a strike indicator and small split shot is the basic setup. Adjust your depth of the strike indicator after identify where the fish are feeding in the water column. At times a split shot is not necessary. Do your best to identify the color and size of the midge to match your selected fly. Since the hatch is quite prolific, trout key on the specific bug so finding that perfect imitation is key. I recommend having a variety of colors in the size #16 and #18 range, patterns are listed below.

Recommended Flies: Olive/Black Biot Midge #16 and #18, Olive/Black/Gray Sparkle Wing RS2 #16, Black/White/Olive Soft Hackles #16 and #18,  Buckskin Caddis #16 and #18.

Guide Tip: Focus on a slow rod pickup as you begin another cast. Often when trout are keying in on emerging insects they will feed when the midge has the slightest of movement. Using a longer softer action rod can be a lot of fun fishing this hatch.

Where does it happen?

Like most hatches, the “midgezilla” is based around water temperatures. Looking for water temps in the 42 degrees to 48-degree range as it is prime for this hatch. Locally, the bugs can be found on the Lower Roaring Fork River, Carbondale down to Glenwood and onto the Lower Colorado River through Glenwood and into Rifle. Unlike Blue Winged Olives this hatch can occur in sunny conditions as well.

Book a Guided Trip

Vail Valley Anglers offers guided fly fishing trips year round. If you are looking to shorten the learning curve with this hatch, call or stop by the shop to learn more about our guided trips. We offer Half Day Wade Trips on the Eagle River and Full Day Floats on the Roaring Fork and Lower Colorado Rivers.

Check out our updated fishing reports here for latest conditions on our local streams.

Patrick Perry Content Contributor and Former Guide