Pro Tips: How to Fish Southwest Montana’s Early-Season Midge Hatches

Written By: Brian McGeehan, Montana Angler

Adult midges blanket the water as a fly angler works the far bank.
All photos by Montana Angler

Fishing with midges is great here in southwest Montana during early spring, as trout begin to key in on these tiny yet abundant insects. Midges are often the first–and sometimes the only–aquatic insect emerging at this time, so they tend to draw consistent strikes from hungry trout until mayflies and caddisflies begin to divide their attention later on. The strongest midge hatches run from late February through early May, but there are many different species, and they remain an important food source throughout the year. (In fact, midges account for half of many trout’s total caloric intake over the year). Understanding a few key details of the midge’s lifecycle–from larva to pupa to adult–will help you to better imitate these flies this spring. 

Extreme close-up of an adult midge crawling across a snowbank, showing their delicate anatomy.

1. Larva

Midge larvae are small, wormlike creatures that are poor swimmers, and prefer to attach themselves to rocks, aquatic plants, submerged woody debris, or to just burrow into the mud. They are frequently dislodged from these positions, however, and are then pushed downstream near the bottom, which is where your flies should be too when imitating this stage. I use a typical nymph rig, with a strike indicator set roughly one-and-a-half-times the water depth above my split shot, which is pinched on about a foot above my first fly. Morning is the most productive time to fish with midge larvae, before the day warms up and the hatch begins. As far as fly selection goes, you can keep it simple with a Zebra Midge. Be sure to have black, red, and gray versions handy in sizes 16 to 20.

Sneaking up closer to the fish allows you to make more accurate casts, which are at a premium while fishing small flies on light tippets.

2. Pupa

Midge pupae build up gasses beneath their exoskeletons as they prepare to hatch, which causes them to begin rising upward in the water column. When the pupae reach the surface film, they pause and rest for a brief time before emerging, making them easy meals for trout. If you can see fish feeding in the surface film, a “greased leader” approach works well: remove your indicator and split shot, and apply floatant to the last couple feet of leader and tippet above your flies. This will keep your midge pupae suspended in the surface film. If the trout are feeding deeper, it may be better to return to a traditional nymph rig, so be prepared for some trial-and-error until you find the right depth. I like to use patterns such as the Smokejumper for this stage, and I’ve also found that midge pupa flies incorporating a clear glass bead can be very effective. 

During heavy midge hatches, try drawing attention to your fly by using a cluster pattern such as a Renegade.

3. Adult

Eventually, the pupa sheds its exoskeleton and emerges as an adult midge. But many are not strong enough to break through the water’s surface, and so they remain trapped in the film with their exoskeletons still dangling from their abdomens. Trout key in on these helpless midges, which is why selecting a dry-fly imitation with a trailing shuck, such as the Skittering Midge, can produce such great results. The adults that do break free often tend to cluster together in large groups on the surface, creating a big meal that trout will seek out. When fishing dries, there are often so many midges on the water that fish do not have to move far to get them, so careful observation, stealth, and accurate casting are all vital to your success.

Brian McGeehan is owner and operator of Montana Angler in Bozeman, MT.

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