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Mike's Iowa 'Hatch Chart'

by Mike M

Here in Iowa, we’re fortunate to have several insect species that produce sizeable hatches at different times of the year. While not quite as predictable as the hatches in some other parts of the country, these hatches can still be anticipated if one knows what to look for.

What follows is an Iowa version of a “hatch chart” – a list of insects one would be likely to encounter at a given time of year and the patterns best suited to imitate them. This information has been drawn from the collected wisdom, experience and observation of the many posters on the Stream Fishing in Iowa website and so a huge thanks is owed to each of them!


While stream trout fishing closes in our neighboring states through some or even most of the winter, it is alive and well in Iowa. Indeed, some trout fishermen claim winter as their favorite time to be on stream as they are almost certain to have said stream entirely to themselves. If you’re brave enough to head out to a stream in the middle of an Iowa winter, here’s what to look for.

Insect wise, midges will be your quarry this time of year. Midges hatch nearly every day, all year long. While midges are quite tiny, trout (sometimes large ones) will rise to midges especially if they are the only fly hatching. If fish are rising to midges on the surface, it’s hard to beat the standard Griffith’s Gnat in a size 20-24.

On a warm winter day, especially early and late in the season, we can, at times, be treated to decent hatches of Blue Wing Olives (a species of mayfly). These bugs will be very small and I’ve often found the smaller the fly the pickier the trout become for a precise imitation. So, while at some times during the year, a fly like a Parachute Adams will consistently pick up fish during a Blue Wing Olive hatch, this is the time to have a Blue Wing Olive dry fly. Again, sizes will be small (20-22).

Most winter fishing will happen subsurface. Nymphs dead drifted will pick up fish throughout the winter. A beadhead Pheasant Tail, Hares Ear or Copper John nymph in a size 18 or 20 will likely produce fish on any Iowa stream in the winter. Fish will typically not move a great distance for a fly in winter, so this is the time to get your fly deep and right in a fish’s face. Added weight through split shots or double nymph rigs are well suited to getting flies where they need to be. It’s often said: “If you’re not hanging up on the bottom from time to time, you’re probably not deep enough.”

Winter can also be a good time to hunt for larger trout by dead drifting or very slowly stripping a streamer through longer runs and deeper pools.


Depending on the ferocity of the preceding winter, spring fishing in Iowa is better thought of as two, or perhaps even three, distinct seasons. Early spring will, at times, be an extension of winter. Sparse hatches, small flies and cold hands can often run into the month of March. At other times, however, the snow has melted and the temperatures have warmed and the bugs are beginning to get active by this time of year.

Mid-March brings the first non-midge hatches of the year. As you venture out to the streams, look for small Blue Wing Olives (which will increase in size as the temperature warms) as well as small black stoneflies.

Late-March to early April will typically offer the first caddis hatches of the year as well as bigger Blue Wing Olives and some continued stonefly hatches. This can be a great time to fish a heavy beadhead caddis pupa or mayfly nymph pattern followed by a smaller Pheasant Tail, Hare’s Ear or Copper John. One of my favorite set ups for spring fishing is a size 12 beadhead nymph followed by another beadhead nymph in size 18. The size 12 fly will not only serve to get the flies deeper, but I have a hunch it also serves as an attractor which draws fish to the smaller, more realistic size 18 pattern. I will continue to fish this set up all the way through the fall slowly increasing then decreasing the size of the second fly.

In a normal year, Dark Hendricksons will begin to appear in early to mid-April and can be prolific on some northeast Iowa streams. It’s been my experience that Hendrickson imitations need to be rather exacting in their coloration, so make sure you carry several dark brown bodied dry flies this time of year. The Hendrickson mayflies tend to be larger and can usually be imitated by a size 14 or 16 fly. A fishing buddy and I have found it hard to beat the old Red Quill Dry in these sizes.

As the temperatures continue to warm into May, the bugs only get bigger and more active. Mid-May will bring the first Sulphur mayflies. While this hatch isn’t always big or predictable like some others, there are years when it can be sizeable and frequent. A size 16 Light Cahill or Sulphur Dun will fish quite well during these hatches.

Late May and early June bring the biggest of northeast Iowa’s mayflies: the March Browns and the Gray Foxes. These two mayflies are closely related, but still differ in their coloration. While March Browns display a darker body, the Gray Foxes tend to have a brownish-yellow hue. In either case, the flies are big (around size 12) and trout will rise readily to them. If you have the chance to fish a March Brown or Gray Fox hatch, which typically occur in the late afternoon or early evening, it’s not to be missed! A Parachute Adams in a size 12 can provide one of those evenings on the water that leaves you wondering if it could get any better!

As fish become more active after a long winter and water levels remain high with runoff, spring can also be a good time to fish streamer patterns.


Summer provides a bit of a lull in insect activity. Nymphs will continue to be active and hatches, when they occur, will typically take place later in the day. Yet, while many aquatic insect hatches die down during the summer, land dwelling (terrestrial) insects are just beginning to become their most active. As streamside grasses and weeds flourish and trees grow full of leaves, grasshoppers and crickets, beetles and ants often play dangerously close to the water’s edge, while trout lurk below waiting for one of them to lose their footing and become an instant meal.

When one thinks of terrestrial fishing, grasshopper patterns usually come to mind. And while a warm, drier summer will often mean good hopper fishing in northeast Iowa, don’t overlook the other terrestrial insects. On tree lined streams, ants and beetles can bring many surprisingly fine fish to hand. While a typical “dry fly dead drift” works, don’t hesitate to let your fly sink below the surface film and fish it as you would a nymph. I’ve had days of fishing where 3 of every 4 fish take a terrestrial below rather than on the surface. Another productive way to fish a terrestrial is to drop a nymph via an 18” piece of tippet knotted to a hopper, cricket or beetle pattern. The terrestrial will float and serve as a strike indicator, while also being capable of hooking a fish should they prefer it. Don’t be surprised to see a fish rise to the terrestrial only to take the nymph.

Think about terrestrials the same way you think about mayflies in the spring: fish smaller patterns early and bigger patterns as the summer rolls on. With the right conditions, terrestrial fishing can continue well into September. One September day a few years back, a friend and I were fishing his favorite Iowa stream. Neither of us could buy a fish until, just as we were about to leave, he tied on a large foam hopper and on his first cast took one of the finest browns I’ve seen caught in northeast Iowa. We headed to another stream and proceeded to catch a few scattered fish on hoppers. I then switched to a small black ant pattern and began taking fish on almost every cast. It may lack the subtlety of fishing a small Blue Wing Olive hatch, but I find terrestrial fishing hard to beat.

Summer evenings can often bring decent to prolific caddis hatches. In flight, caddis look like small moths. Their wings are tan to gray in color and the flies typically have either an olive, gray or cream colored body. Unlike mayflies, caddis hatch in faster water, which means two things. One, you can get away with fishing a larger pattern making your fly easier to track. Two, rising fish will hit your fly very hard. At times, caddis will hatch alongside mayflies. When this happens, it’s sometimes necessary to determine which bug the fish are feeding on. To test this, simply determine the type of water where fish are most active and the type of rise you see fish making. If the rises are of the splashy sort and are occurring in faster water, it’s a safe bet the fish are feeding on caddis. An Elk Hair Caddis in size 12 or 16 has covered just about any caddis hatch I’ve encountered in Iowa.

If you have a good pair of polarized glasses, start watching in faster sections of water around 5pm on a summer evening. Often you’ll see fish slashing through the water column as they feed on caddis on their way from the nymphal stage to winged adults. I’m not much of a wet fly fisherman, but I’ve watched other members of this forum take fine fish while swinging an appropriately colored wet fly through these types of runs while I dead drifted weighted nymphs unsuccessfully. A wet fly with an olive or tan colored body fished somewhere between the surface film and the streambed will almost certainly take fish.

One big tip as you fish caddis emergers or dries: Impart action. Caddis are very active insects, literally rocketing out of the water as they hatch. Trout, in turn, seem to enjoy chasing them! Likewise, caddis returning to the water to lay eggs rarely float downstream in a stationary manner as their mayfly counterparts so often do. They flutter and skitter all over the water’s surface and often a fly “skated” across the water’s surface will take fish more successfully than a dead drifted one.

Summer will be the time to pull out your largest nymph patterns. I’ve often done double takes when I see March Brown nymphal shucks floating through the water as they look more like a drowned fully grown cricket than something that once housed a mayfly. This is also the time where you’ll find the most Rhyachophilia or “Green Rockworm” caddis pupae crawling on the bottoms of rocks. A size 12 caddis nymph trailed by a smaller size 14 or 16 mayfly nymph should produce many fish during the summer months. In recent years, I’ve grown especially fond of fishing Czech style nymphs to imitate these Green Rockworms. Czech nymphs are tied with more weight than the standard beadhead nymph pattern. They are also tied on scud (curved) style hooks, which perfectly imitate the curly, segmented, wormlike caddis pupae. An olive Czech Mate pattern in size 12 serves as a great “point fly” to get my flies deep, but also picks up many fish itself.


Like spring, fall fishing in Iowa is best thought of as two distinct seasons. Early fall – through mid-October or so – is really an extension of late summer fishing. Terrestrial fishing is still a possibility, especially with ant patterns. Caddis hatches will slowly die off, but Blue Wing Olive hatches will tend to pick up again. On a cloudy, drizzly fall afternoon, don’t be surprised to run into a goodly sized hatch. Blue Wing Olives in early fall will be larger than in early spring, running in the size 14 to 18 range and exact imitations likely won’t be as necessary as they were earlier in the year. I often prefer a Parachute Adams if I can get away with it as I find it easier to see on the water.

Late fall – late-October through Thanksgiving – will bring the last Blue Wing Olive hatches of the year. Flies will be small – size 18s all the way down to 22s – and hands can grow cold quickly, but good dry fly fishing can still be had this time of year.

However, successful fall fishing will usually mean nymph fishing and successful nymph fishing will mean mayfly nymphs. Again, it’s hard to beat a Pheasant Tail, Hare’s Ear or Copper John or some combination of the three. Start downsizing your flies as the water cools and the days get shorter. By Thanksgiving, size 18 to 20 nymphs will be the rule.

As brown trout prepare for the spawn (be on the lookout and try to avoid their spawning redds), fall can also be a great time to aggressively fish large, brightly colored streamer patterns. One of my favorite streamers for this time of year has bright yellow marabou and bright yellow rubber legs. I have absolutely no idea what the fish think it is, but they love it!

Summing it Up: A Basic Fly Box

Here’s a question we’ve discussed many times on this forum, but it’s a good question. What would a very basic Iowa fly box look like? If you were to open the boxes of several anglers, you’d almost certainly find differences. Yet, you’d likely also find some very key foundational flies that cover all aspects of the life cycle of the most important aquatic insects in Iowa. And so a very basic Iowa fly box might look something like this:
1. Beadhead Pheasant Tail, Hare’s Ear and/or Copper John in size 12, 16, 18 and 20.
2. Parachute Adams in sizes 12-18
3. Blue Wing Olive dry pattern in sizes 14-22
4. Elk Hair Caddis in sizes 12-18
5. Griffith’s Gnat in size 20
6. Wet fly of choice in sizes 14-18
7. Terrestrial(s) of choice in sizes of choice
8. Streamer(s) of choice in sizes of choice

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