Becoming Familiar With Hatches

It’s a complicated world out there, the first time you dive in.Pteranarcys californica, Drunella grandis. It’s enough to send you back to the Royal Wulff and a Prince nymph. Which makes sense, because why does the Prince work? It’s the nymphal form of the Royal Wulff! That’s a fly joke. You’ll get it before you finish reading this, promise!

Insect identification is much easier than you think. Look at it this way. A guy walks down the street with a Chihuahua on a leash, and you think, nice dog. Right after comes a woman walking a Great Dane, and you think, nice dog. Now what on earth made you think those two animals were related to each other? Well, it starts with familiarity. 4 legs. Elongated snout, wet nose, fur, canine teeth. Despite the size and color disparity, you know they’re both dogs. Because you’ve grown up around dogs, seen them all your life. It’s familiar.

As you spend time on the water, the sight of the insects will also become familiar. They’re smaller than a Great Dane, and no one will have them on a string, so you need to pay a bit more attention and look for them! Noticing the different way various aquatic insects fly, or the way they emerge. Once you start looking for insects, the differences and similarities all becomes second nature, just as recognizing a dog did. And here’s another very positive thought about insect ID. You don’t need to know the Latin name, or even the common name, of every bug that flies by. If a pale olive bug 11mm long flies by on July 5, find a fly in your box that’s pale olive and 11mm long, and tie it on. Simple as that. If the Missoulian Angler Fly Shop has done its job, you have that 11mm pale olive fly, and what they are and represent is less important.

But there comes a time when you do want to know, and we get it. Mayfly or House fly. Stonefly or Fruit fly. The MAngler has created a large online resource page called Hatches, which if we do say so ourselves, is pretty spiffy! Look at it, and the images will give you a good idea of what a caddis fly, mayfly and stonefly will look like. You’ll also find images later in this section as well. Those are the big three. Sure, there a lot of other insects present in water, including Midges, Crane Flies and a myriad of others. But the food forms most trout (and therefore most anglers) focus on a lot of the time are caddis, mayflies and stoneflies. 

When you’re on the water, if you carry a net, looking at the real thing is a very simple task. Get a stocking and stretch it over your landing net. Instant bug net, suitable for subsurface or in-flight grabbing. It’s easy to carry and store, and you don’t have an extra piece of tackle with you. There are also commercially available bug seines for this purpose as well. Start by kicking a few rocks directly upstream of the net, which is touching the bottom directly downstream of where you’re moving rocks. Look at what precipitates into the stocking. It will take a minute to get the hang of keeping the seined materials on the face of the stocking, but you will. You’re going to find more in the seine than just bugs! You’re going to have to move some stuff around to find the insects. Look and see what you’ve found. Are they big? Small? What color are they? How many of each are you finding?

Once you’ve done that a couple of times, you’ll have a feeling for the prevalent insect. If its brown, and 11mm long, tie on a nymph that’s brown and 11 mm long. Trout are looking for the easiest meal they can find, the least difficulty in feeding. When you’ve determined what the most prevalent insect is on the water, you can be pretty sure the trout are focusing on that food source as well. Its plentiful, and requires less work to locate. That’s the reason you seine, to find what the trout are going to be most likely to be feeding upon. Think of it this way. If you were in a room stacked to the ceiling with apples, with about 60 oranges in amongst all those apples, what’s the easiest thing for you to eat? Apples. The same applies to trout looking for food.

You’re going to look like a foolish fish, running down the river in waders, waving a landing net in the air and cursing as your swipe completely misses the mark. A foolish fish is defined as a Dumb Bass. (Say it three times fast, out loud. You’ll understand.) Get over it! We’ve all been there, we just don’t talk about it anymore!!

Every time you head to the water, think about this. You’re a predator. An average hunter knows his quarry. A good hunter knows what his quarry needs for survival, including what it will be feeding on at any given time of the year. We’re not on the plains of Africa, where predators congregate around water holes. Our prey lives in the water, so that doesn’t work! We have to learn about what our quarry is after in other ways. When walking to the river, you’re paying attention. See a spider web? Look at it carefully. What’s in it? Shake a few branches next to the river as you walk AWAY from the put in.

You’re paying attention to your surroundings. You’re looking for information about possible food the trout might be eating, and taking the proper steps to ascertain what the most abundant food form is. Shaking branches, looking for shucks along the shore, spider webs, these are all things good anglers do to figure out what the trout are most likely to be feeding upon.

Aquatic insects are cyclical. If you see that pale olive insect in July this year, you’re going to see it again next year at the same time. The MAngler has a Hatch Chart in our Resource pages as well, detailing the insects important to the trout. The chart shows what species, size, and when it’s likely to be found on the Blackfoot River, Clark Fork River, Rock Creek and the Bitterroot River. When you’re out on July 5, look at the hatch chart. It will give you a starting point to insect ID, because you can eliminate a lot of insects that won’t be on the water at that time of year. And you start looking at the bugs on the water.

On July 5, you see fish rising, and there’s a bug on the water that’s pale olive and 11mm long. You catch one, and it has an elongated body that curves upwards, 6 legs, large eyes and the wings stick straight up and back over the body. You’ve done some research, (or used your phone to access the Hatches Resource Page) and you ID the shape as a mayfly. Boom! It’s on like Donkey Kong! It’s like figuring out your first dog. The hard step is over. Now, any time you see that shape, regardless of size or color, you KNOW it’s a mayfly. The rest will follow, names, emergence times, etc. It’s a time and familiarity thing.

The same will happen for stoneflies and caddis. You’ll ID your first one, and all of a sudden those worlds open up as well. And then, the river starts to look like a bug hatchery. When you’re not sure what exactly you’re looking for, it’s really difficult to find it! But as you spend more time on the water, and start to see the insects as stoneflies or caddis, all of a sudden they seem to pop out for you. You’ll be stunned you missed it all the other times you came to the river. You start to understand what the birds are doing, wheeling across the surface of the water, and can now use their actions to locate insect activity. Behavioral and cyclical patterns will start to emerge on the river, patterns that will provide you more successful angling in Missoula, and anywhere else you take the long rod out for trout.

It’s a big step, learning to ID the different insects on the river. We know anglers who aren’t comfortable without knowing Latin names, the range where they’re found, life cycles and the factors that trigger their emergence. Some just want to know the name so they buy the right flies! Other could care less, and just go a-fishing. Find your own comfort level, and don’t be influenced by others. At our Missoula fly shop, we have customers who really care, and we have ones who used to care. It’s all good! Fly fishing is supposed to be fun, and it’s up to you to decide the level of fun you plan to attain. No matter what level of entomologist you plan to be, the MAngler plans to be there helping you get to the level you’re striving for, online and in the shop.

Steps To Identifying The Big Three.

We’re going to start subsurface, and launch the discussion with mayflies, because it’s traditional to start with mayflies. More has been written about mayflies than all the other insects combined. We’re not going to argue, we’re just going to follow in the footsteps of anglers through out the centuries.

There are two critical areas of identification for mayflies, and one lesser stage that we also need to recognize. But we’re starting at the bottom, where the fish live, and the nymphs live for 364 days a year. Once we’ve examined the mayfly nymph, we’ll contrast it to the Stonefly nymph. The nymph is the subsurface stage of the adult mayfly, as it lives on the bottom. They have 6 legs, an exoskeleton, 2 or 3 tails, abdomen, prominent thorax and tiny head, as you can see in the photo. The abdomen contains the adult mayfly’s body, and the thorax contains the wings. With this general information, and a little practice time, you can now identify mayfly nymphs from caddis pupa and stonefly nymphs. If you want to actually find out what the nymph is, down to genus and species, you do things like count the tails, compare dorsal and lateral gills, compare size of the prothorax, mesothorax and metathorax, count the abdominal segments, check for forked claw on tarsus, and measure with a flexible, accurate ruler. You know, things like that. It’s what biologists do. We might not have to go that far. We’re just going to count legs, get a general size and check the color. With that done, we go to the Hatch Chart, and start eliminating what it’s not! Not scientific, but it’s what we need as anglers.

In your seine, you might also find some stonefly nymphs. If you look at the picture, you will see they also have 6 legs, two tails, and an elongated thorax with an extra wing pad. Stonefly adults have two sets of wings, which means they need two thorax areas to gestate those wings. Other than that, they look and act pretty similarly in the water. It feels like they will be tough to tell apart, but not as much as you think.

Finding stonefly nymphs definitely depends on where you put your seine. If you choose to look for nymphs in slower moving water, you will find few stoneflies. If you get in the middle of a riffle and seine, you’ll find many more. The stonefly has evolved with a very rudimentary gill system. Think about those rocky riffles as being the aerator for the stream. Because the stonefly’s gills are less functional, they need to live in highly oxygenated water, like the stony riffles. It’s how they got their common name, stoneflies.

It’s also pretty easy to tell the majority of stonefly nymphs from mayfly nymphs due to size. The average mayfly nymph is about 10mm long. The average Missoula area stonefly is about 25mm, with some reaching 50mm. That’s a pretty big size variation, and makes separating stoneflies from mayflies pretty easy. But there are smaller stoneflies throughout the Bitterroot River, Rock Creek, the Clark Fork River and the Blackfoot River. Telling the smaller stoneflies from the larger mayflies can be a bit tricky at first, but it might not matter as much as you think it should.

While it’s true the stonefly has an extra wingpad, and may be a bit bulkier than the average mayfly nymph, here’s something to think about. Trout are not counting wingpads, or tails, or checking out claws on tarsus. They are looking to eat, and their eyesight in the water is attracted to movement and general shape. If they could see well enough to count wingpads, do you really think they would accept food with a giant piece of metal sticking out of its butt? Highly doubtful. So a smaller stonefly nymph can be imitated by a larger mayfly nymph. Not as well, but it will work. As you get deeper into this, you will want smaller stonefly nymph imitations, but as you begin, just match size and color.

Match the size first. That’s most important. Imagine you’re a hunter during antelope season, and an animal is approaching. What’s the first thing you’re judging, as a predator? Size is the first determining factor. Not color, not hoof shape or tooth count, but size. It’s the same for the trout. It’s human nature to say, “I don’t have the exact imitation for this nymph.” You know the nymph is brown, so you reach into your box for a brown nymph, even though it’s 4mm smaller than the natural. Most trout will reject it out of hand, because the size doesn’t correlate to the natural. Better to choose a different color nymph in the same size, so it’s not rejected, at least immediately. It’s best to have the proper imitation with you, but that’s going to take some time!

We haven’t said much about the caddis yet, and this is why. The stonefly and mayfly have a similar three stage life, and behave in a related manner underwater. The caddis is a four stage insect, and has a completely different behavioral pattern. The caddis larva spends its life creating a protective case or place in which to pupate. Some caddis larva spin webs underwater to provide protection. They use their web spinning ability to slide out of their web, attached to a life line of web, and forage- pulling themselves back to their web when finished. Other species of larva, as they grow, create a case surrounding them. These cases look like little stone tubes made of sand grains and other detritus found on the river bottom. They carry these cases with them as they forage, adding on to them as they grow. Inside their case or web, the larva resembles a small, segmented worm. If your seine pulls up a bunch of rock tubes or small segmented worms, you’ve found caddis larva.

Caddis, mayflies and stoneflies all leave their subsurface life for a land-based existence in different ways. The mayfly nymph, when nature calls on it, rises to the surface. They break through the surface film (meniscus) and extend their wings from the thorax. Once the wings are erect, they float along the surface waiting for them to dry. Once dry, the mayfly flies away to live for 24 hours in the trees or shrubs found near the water. Their distinct shape, as shown in the picture, are often likened to a little sailboat, and their actions on the surface help to identify these insects as mayflies. It’s the floating along the surface that really identifies a mayfly. In cool, wet weather, they may float for 30 feet before being able to fly. It’s why fish key on them. Many times they are vulnerable to the trout as food for quite some time.

Stoneflies exit the water in a completely different manner. When their biological clock says it’s time to hatch, they crawl up onto shore to escape their exoskeleton. When walking the rocky shoreline of a river, look for these almost clear husks along the edge of a river. The more husks there are, the more stoneflies are about. Once they’ve exited from their exoskeleton, they fly to the nearest tree or shrub, where they live anywhere from one to three weeks. The females return to the river to lay eggs, dancing across the surface as she drops the eggs back into the river.

The caddis, about a month before its emergence, has huddled back into its case or web, and is pupating. It’s going through the same metamorphosis as a butterfly does. Once it has pupated from larva to adult, it will release itself from its protective case and float rapidly to the surface, where it will burst through the meniscus as a fully fledged adult, and again fly to protection. They live from 2-3 weeks on average, and again it’s the females who return to the river to lay the eggs.

The only one of the big three to actually hatch in the river are mayflies. They emerge from the water, onto the surface, where they float along getting ready to fly away. Saying a hatch of stoneflies or caddis is a misnomer. What constitutes a “hatch” of caddis or stoneflies are really the females coming back en masse and laying their eggs. In a perfect world, they would never enter the water again, but often they get swamped and are trapped in the surface. At other times, the fish will see these insects dancing on top of the water and take a slashing rise at them. But again, it’s not a hatch, just a return to the river for procreation.

It’s quite easy to tell a mayfly from a caddis fly or a stone fly. A mayfly’s wings stick straight up. Caddis and stonefly wings lay straight across their backs. Mayflies and caddisflies tend to be decent fliers. Many mayflies have a very distinctive flight pattern in the air, and can be identified from that. Stoneflies in flight however are not graceful. They tend to fly in a herky jerky way, and will have 4 wings instead of two. If you see any stoneflies or caddis in the air, think about tying one on. It means they’re coming to lay their eggs, and the fish will be looking for them. With mayflies, the most (but not all) success is found by being on the water when and where they’re hatching. That takes time to learn, and the MAngler is here to help.

The mayfly also offers a third stage that can be imitated by the fly fisher. When the mayfly has completed its 24 hour life cycle, they will often return to the water in the last stages of life as a spinner. A spinner is very difficult to see on the water, as the mayfly has lost the strength to keep its wings upright. They float down the river, wings spread out in the surface film. When this happens, the fish will come up and take these spent insects as readily as the adults. Some mayflies have spinner falls during the hatch. If you find yourself out during a spinner fall, you’ll need a specialized fly to provide the correct imitation.

Lets recap. The Royal Wulff represents nothing in nature, but is based on the classic mayfly fly design. The Prince nymph represents nothing in nature, but is based on the classic mayfly nymph design. Since all mayfly adults come from nymphs, it’s logical to think the Royal Wulff has to spring from somewhere as well. Hence the success of the Prince. Glad we cleared that up.

We hope this has made insect identification a little less daunting. Made it, in fact, a little more familiar! Because familiarity is what it takes to start telling the caddis from the mayflies from the stoneflies. Do your research. Utilize the life cycle charts and hatch chart found on the Missoulian Anglers web site to familiarize yourself with how the bugs interact with the water, and when you can hope to find them. Armed with that knowledge, and little time on the water spent looking at your surroundings, you’re going to find this mysterious world of bugs is not as complicated as some anglers make it out to be. Sure, it’s fun to pontificate about the difference between Ephemerella inermis and Ephemerellainfrequens, but is it really necessary? Only if you think it is! So take from this what you need to catch fish, or what makes you happy, and then use this knowledge on the water!  Unless you’re in an entomology class at the University of Montana, it’s the only place it’s ever going to be useful.

*Midge has a double meaning to fly fishermen. Technically, a midge is a 6-legged insect belonging to the family Diptera. They can be as long as 11mm, and as small as 3mm, with specific characteristics that identify them as belonging to the Diptera family. Fly fishers will also use midge as a term to describe when they are fishing very tiny flies, whether they be of the family Diptera or not. See, we can nerd out on bugs when we have to!