What is a Midge? Know your Fly fishing Bugs

If a trout were filling a fly box, he’d probably grab a whole lot more midges than most of us are carrying these days. Which is a mistake, because midges are the most prolific and diverse of all the aquatic insects that trout like to snack on. Think of them like a bag of chips- they don’t make a meal on their own, but if you’ve got a bag and a couch to post up on, you’re gonna put a whole lot of ’em away. This might be a little lowbrow as far as analogies go, but for trout midges are the same way. A trout sitting in a comfortable hold will stuff themselves on midges as long as the supply is there.

Midges are like the ladies, they love a man in neoprene and khaki.
Photo by Lees Ferry Anglers.

The fact is, there isn’t much water that midges don’t live in, and their biomass can be in the tens of thousands per square meter if conditions are ideal. Like chips, midges come in endless flavors and they’re everywhere. For tailwaters like the Missouri and the Colorado, midges are the lifeblood of the river, and casting tiny bugs to wary fish is as addictive as fly fishing comes. Fly fishermen that focus on lakes also place a high priority on fishing all stages of the midge life cycle.

Perhaps because of their importance on tailwaters and lakes, many of us forget the role they play in other fishing situations. This is a mistake. Midges are a reliable option throughout the year, and knowing when to tie one on will increase your fish numbers.

But let’s not gloss over the real reason most midge patterns don’t see a lot of play: midges are small. 6x and 7x tippets are no fun to work with, and though catching fish on a size 24 is a blast. If going small is something you avoid in your fly selection, make it a point to give it a shot on the river more often. For many of us, stepping out of the pattern rut takes a marked effort. With packs and boxes full of other tasty options it sometimes can be too easy to have good intentions of trying something new, and somehow that row of Royal Wulffs keeps calling us back. A quick tip that can help you avoid this scenario: go minimal and leave everything but the midge box in the truck next time you’re at the river. You might be uncomfortable doing it, but you’ll force yourself to become comfortable with the micros.

Most flyfishermen use the blanket common name “midge” to cover the thousands of sub-species of midges that abound in trout water, though it’s not uncommon to use “chironomid” as a blanket term as well, which is technically the taxon of the insect family in nerdspeak. You can get all graduate student if you want to, but its much more crucial to know what it is we’re trying to imitate than it is to spout greek names. The life cycle of the midge is much more essential knowledge for anglers, as it dictates fly selection.

What is a Midge?
Midge are small aquatic insects that closely resemble mosquitos without the proboscis. Midges begin their lives as quick-hatching eggs in the water that develop into larva roughly averaging in size from a millimeter to a centimeter. These larva vary in color with most prominent being brown, green and red and are like thin, segmented worms. The term “bloodworm” is often used to describe the midge larval stage.
Midges spend most of their lives as larvae in burrows in the river bottom, eating muck, venturing out for a look see around the neighborhood from time to time. Because midge larvae burrow into the silty river bottoms and eat muck, slow moving sections and debris-filled pools are great midge larval habitat. These waters are often oxygen-deficient, which gives midge larva their most prominent feature: bright red hemoglobin throughout their bodies. The larval stage is a viable fly option, and there are scads of simple patterns that copy the thin red bodies.

The S.S. Midge Larvae by Outsmarting Fish is a great option for deep, slow moving pools.
Pattern available at http://outsmartingfish.com/2010/12/midge-larvae/

But when a brief metamorphosis from larva to pupa occurs underground and propels the midge upward in the water column, it also takes a starring role for fly fishing. Midge pupa fill their skins with gas, and wiggle their way to the surface. This portion of the midge’s life is filled with peril, and trout take advantage of their slow journey with abandon. Patterns that imitate this pupal stage pick up on the shine of the bug underwater, and the gas bubble that forms at the pupa’s head. This journey is marked by the pupa’s attempt to break free from the surface, where the gas bubble becomes a trap they must overcome. These surface film struggles are most often a trout’s smorgasbord. Fish can eat in a leisurely fashion, returning to the surface film like a fat elderly woman on a rascal at the Golden Corral. Oftentimes, this is where we will see fish in a holding pattern, working feeding lanes and filling their guts.

A midge pupa pattern is usually a simple proposition.
This size 20 foam emerger is a favorite.

The winged adult must emerge from it’s shuck in the surface film if the midge is going to survive, and this process is daunting. Often, water temperature will halt the pupas ascent, and the midge will hand in the water column at a certain depth as they wait for conditions to change. Trout like it easy, and these snacks are drive though access. 

The Griffith’s Gnat does the trick for surface-riding midges.
Photo via roundrocks.com

But for those that make it to adulthood, once their wings are dry they are off and running in the dash to find a mate and reproduce. This stage kinda looks like a bar at closing time- bunches of males swarming around females that move from group to group, selecting mates. Once mating has occurred at the male’s streamside bungalow, the female returns to the water to lay her eggs, and the cycle begins anew. Which for fly fishermen, is a good thing. Classic midge patterns like the griffiths gnat do a great job of imitating this “buzz ball” midge surface mess, and if you’re not carrying a few in your box you’re doing it wrong.

Knowing a bit about the lifecycle of the midge can help you make the move to those small sizes in your flybox, and there are plenty of resources out there to help you along the way. Get clicking and get to know midges, or better yet- head to the river and tie one on. It’s that time of year.


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