Last week we collected our first sample of bugs from the Missouri River below the Untouchable’s Bridge. The bugs that we collected were about what you would expect for April. Sows and scuds composed the majority of the biomass, but midges and blue-winged olive nymphs were abundant too. Somewhat surprisingly, PMD nymphs were abundant and almost the same size that they will be in June.
You could fish a sowbug pattern every day of the year and expect to catch fish. They are abundant in every section of the river. Many times, people confuse sowbugs and scuds. Sowbugs look like the common garden bugs known as “potato bugs” or “rolly polies” or “pill bugs.” Their bodies are compressed front-to-back making them look flat. Our favorite patterns for imitating them are the Tailwater Sowbug and Ray Charles patterns in sizes 14-18.
You could fish a scud pattern every day of the year and expect to catch fish. Year after year, the Rainbow Czech nymph is regularly our shop’s #1 selling fly and for good reason. There are many scuds in the river throughout its entire length and scud patterns are incorporated into most two-fly nymphing rigs. Whereas sowbugs are compressed front-to-back, scuds are compressed side-to-side. This is why sowbug patterns look flat and scud patterns look like small, curved shrimp. If you’ve never seen these bugs, you should pull up some aquatic vegetation the next time you are on the river and get to know some trout food.
There are two main types of scuds in the river. Big ones and little ones. The ones pictured here are all little ones (around size 18) but there are also many big ones that can be as large as size 10. Scuds have gray-green coloration that fades once they have died, which is why they look so pale in this picture.
Midges and Blackflies
If you are a dry fly fanatic, your best option right now is fishing a dry midge pattern. Midges produce good spring hatches and are common in the drift this time of year. Midge larvae are commonly black, brown, olive, cream, and red (they also fade when preserved for photos). Our favorite patterns for imitating them are Zebra Midge variations in sizes 16-22. Black zebras with a silver bead are the most popular, but anglers should be willing to experiment with other color combinations as well.
When midge larvae hatch, they generate gas bubbles within their shuck that reflect light. It is likely that trout key in on this characteristic when they are feeding on emerging midges. I really like how the beads in this photo mimic this mercurial, gas-bubble effect.
The spring blue-winged olive (baetis) hatch is right around the corner. These mayflies will begin hatching this month. However, they have been present on the bottom of the river for the past few months and commonly enter the drift. They are small (sizes 18-20) and skinny. The best patterns for imitating them are slender brown/olive Pheasant Tail nymph variations. Skinny patterns seem to work better than overly dressed patterns.
Pale Morning Duns
We were surprised to find so many large Pale Morning Dun (PMD) nymphs in the river this early in the year. They are larger (sizes 16 and 18) than blue-winged olives, generally more brown in appearance, and a little fatter. They occur in a variety of shades and can have many different patterns of striping. It will be a few months before they are hatching, but they still commonly enter the drift and become available to trout. Our favorite patterns for imitating them are similar to what we use for blue-winged olive nymphs – small Pheasant Tail variations. Many anglers will use a size 18 Little Green Machine to imitate any mayfly species at any time of the year.
There are two main types of caddisflies in the river. There are caddisflies that build cases and there are caddisflies that are free living. Both types are available to trout throughout the year when they enter the drift. UV Tan Czech Nymphs and the Purple or Gold Weight Fly from Dave Bloom are good patterns for imitating them.
While John and I were taking the photos for this post, a couple keen observers present brought up the point that the Purple Weight Fly in this photo does not actually look that similar to either of the flies in the photo. We conceded that this is true, but it is undeniable that this fly still works extremely well. This is a good example of how fly pattern selection can be abstract in addition to being strictly imitationist. If a trout wants to eat something purple, we are not going to argue with it.
We will continue posting more bug photos on a monthly basis to keep you informed about what is going on in the river. I’m looking forward to meeting more of these bugs in the atmosphere soon. In the meantime, we will have to visit them vicariously through our nymphs.