Fly fishing with my buddy, the “Professor” is like having a live aquatic insect encyclopedia with you, the way he points out bugs all day long. Now he doesn’t know everything, of course, but he is far beyond the basic entomology for fly fishing class. While sitting by the fire in camp I asked him,” When getting your bugs in order, how much fly fishing entomology basics should someone know? It only takes a handful” he said. “Really, about a handful. Yeah, if you know the 5 bugs of fly fishing entomology”.
The 5 bugs of fly fishing entomology to know? 5 groups of insects comprise the basic entomology that most fly fishermen concentrate on. Midges, Mayflies, Caddis, Stoneflies, and Terrestrials. Getting to know the life cycles of these 5 bug groups will take your fly fishing to another level. This is what Paul, “the Professor”, meant by a handful. The 5 groups that make up the basics. Let’s break this down a bit to make sense of it all, OK?
What is Fly Fishing Entomology?
Entomology is the study of insects and is classed as a subsection of zoology. There are more than a million different species of insects and they are the most abundant group of all animals in the world. They live almost everywhere, in every habitat, and have done so for more than 350 million years. Entomology has been crucial regarding an understanding of diseases, better agricultural techniques, biodiversity, ecology, and evolution.
Entomology is a complicated subject but we only need to focus on a few key things. For us, the fly fisherman, entomology is the study of certain bugs living in and around our streams. These bugs are the necessary food source for trout. Learning some basic “fly fishing entomology” will increase our catch. And as we know, it’s all about catching trout.
Why Know The Stages or Life Cycle Of Insects?
Life cycle or stages simply refers to the periods of development insects go through. You might remember from your high school biology class, the term “metamorphosis”. From that class, we learned (assuming you paid some attention) that a butterfly went through 4 stages. Starting out as an egg, hatched into a larva, then to a pupa, and finally as an adult (butterfly).
The same four stages are what fly fishermen concentrate on when imitating the various lifecycles. We fish nymphs, emergers, dry flies, or spinners which we apply to trout feeding behavior. Nymphs are bottom dwellers and nymph patterns need to be fished near the bottom of the stream. Emergers rise from the bottom moving through the water column towards the surface. Dry flies that mimic adults or spinners are fished on the surface.
Knowing when these periods happen and when insects transition from one stage to another is what fly fishermen center their fishing activity on. Along with water temperatures and time of the year, understanding these stages is important to up your catch rate. Why you may ask? Well, think of it this way. Understanding basic entomology helps with fly selection. Selecting the right fly is what catches trout.
In other words, the key thing about this knowledge, when applied to fly fishing, is to equip yourself with the ability to identify the bug family and the stage it is currently in. Next, pick a fly from your fly box that closely matches and present it to the trout.
What Are The 5 Basic Groups to Learn?
As I mentioned earlier, the 5 bugs of fly fishing entomology to know are the 5 basic groups of insects. Once you have a handle on these groups you’ll have enough of a selection to build your fly box. In fact, if you were to only use one or two of these groups you will have enough bugs to choose from, believe me.
Let’s Start With Midges.
The first group of the 5 bugs of fly fishing entomology to know?
Midges are often mistaken for their close relative, the mosquito. They live year-round on streams and rivers and are a favorite of trout. You can identify a midge by its long and narrow scaleless wings that lay back along with their bodies. They are a small critter about the size of a #16 or #18 hook. Males have antennae that are long feathery plumose. They look very much like a mosquito as I mentioned earlier.
There are actually four stages that Midges go through. But we only need to focus on three of those stages, larva, emerger, and Adult. The larva stage resembles little worms with segmented bodies. (More in-depth Look – click) Because of the diet, they appear as a red color. The Midge larva is your basic or standard nymph pattern. These are generally fished just below the water surface and throughout the water column.
The pupa is the emergent midge pattern. During the emerger phase, the pupa takes on a “U” shape and is encased in an air bubble they form to raise themselves to the surface or just below the surface.
The final stage is the adult stage. These guys are very small and by themselves difficult to fish as a dry fly. But, when midges mate they gather in a cluster on the water surface. This is an ideal time for both the trout and us. For trout, it’s a bigger meal of course, and for a fly fisherman, using a pattern like a Griffith’s Gnat is a good choice. Griffith’s gnat mimics this ” mating clustering” of the midges.
Mayflies
The second group of the 5 bugs of fly fishing entomology to know?
A Mayfly is easiest to identify because of its wings. The wings are upright, straight up, and resemble the sail of a sailboat on the water. They typically hatch in the morning and evening hours.
Mayfly Nymphs
Mayfly nymphs fall into one of four groups referred to as swimmers, clingers, crawlers, and burrowers.
- Swimmers are slim and streamlined. They are “minnow” shaped, meaning, they are kind of oblong. This shape provides for ease of swimming along with a three-part fringed tail with fine hair, used to propel them through the water. Oval gills are positioned on the sides of the abdomen for breathing. They do have legs but they are weak and wobbly and prefer swimming as a means to move around. They hide among the rocks, pebbles, and grasses of the stream bed in slower moving water that borders faster-moving water.
- Clingers have flat widebodies and a prominent head with eyes that are located in the dorsal area. They live in fast water and because of their physical abilities, they hang onto rocks in the fast current.
- Crawlers are generally found in the flowing water of streams and occasionally in lakes. They have gills that extend from the abdomen similar to swimmers.
- Burrowers are found in the soft silt or sandy areas of stream beds. They make “u” shaped burrows in the sediment using upturned mandible tusks, hence their name. The gills are also located along the abdomen, which creates a flow through the burrow bringing food particles and dissolved oxygen.
Mayfly Emergers
Mayfly emergers may be one of the most important stages for fly fishermen to know and identify. During the emergent phase, emergers have a shuck behind their bodies as they make their way to the surface film. Once on the surface, they break out of the shuck into the adult stage. During this stage, also known as “molting”, the emerger has air and gases that collect under their protective shell, increasing their buoyancy and propelling them to the surface. Interestingly, during this molting phase, the nymphs are unable to breathe.
Once on the surface (some crawl to shore to molt) they lift their wings to fill with fluid and let their veins harden. (We refer to this as drying their wings but in reality, they don’t actually “dry”). Once the wings are “dried” the emerger is an adult referred to as a “Dun”. Still not sexually mature though, they need to go through one more additional phase or molt. They fly from the water to nearby vegetation where they sit quietly until they molt, or shed their exoskeleton, one last time to become spinners.
Mayfly adults, once through the Dun stage, are now referred to as “spinners”. They are typically recognized during the spinner stage because of their clear wings. Their sole purpose now is to mate and lay eggs Interestingly during this phase they have no digestive system, no working mouth, therefore they don’t eat or drink. They give off a scent to attract a mate, lay eggs, and begin the cycle of life over again.
Caddis
The third group of the 5 bugs of fly fishing entomology to know?
The caddis is one of the most abundant food sources for trout. Trout feed on caddis from its larval stage through and including the adult stages of a caddis’ life cycle. Caddis live as a nymph underwater in streams, rivers, and lakes for up to two years. When ready, they emerge to the surface of the water and fly off.
Caddis larva can be collector-gatherers, picking up fragments of organic matter, while others are collector-filterers, sifting organic particles from the water using silken nets or hairs on their legs. Some species are scrapers, feeding on the film of algae, and still, others, are shredder-herbivores, chewing fragments off living plant material.
Caddis larva resembles a small grub, and during this stage are vulnerable. As a defense, they build a protective case. These portable cases are made out of silk and debris comprised of sand, gravel, or sticks. As the larva grows, more material is added at the front of the case. The case is large enough so the larva can turn around in the tube to trim the unneeded rear end of the case. The case is open at both ends to allow the larvae to draw oxygenated water through the back end, over their gills, and pump it out of the wider front end. Depending on the species, these cases are constructed differently and in some species, the case is replaced by a silk net.
Pupa
Once the time has come for the transition to an adult, the larva goes into a pupa like state sealing the ends of the tube to protect it from predators. When ready, it breaks from the case and is catapulted by formed gases, to the surface where it flies away.
Adult caddis has membrane-like hairy wings, which when the insect is at rest, appear as a roof-like tent over their bodies. Adults are nocturnal and are attracted to light much like a moth. Adults live short lives, most being non-feeders and equipped only to breed at this point in their life. After mating, the female caddis lays eggs in a gelatinous mass and depending on species, attach them either above or below the water surface. The eggs hatch in a few weeks.
Stoneflies
The fourth group of the 5 bugs of fly fishing entomology to know?
Stoneflies are one of the few insect groups that emerge as adults in winter and early spring. Stoneflies, as the name suggests, live in fast-moving, clear streams, with rocky bottoms. Small mountain brooks and streams that flow through wooded areas are a great habitat for stoneflies.
Stonefly nymphs are distinguishable by two tails and two sets of wing pads or plates. Their gills are located in the middle body segment near their legs. They exist in the nymph stage for about a year with a few species lasting three years before maturing. Stoneflies cling to the rocky bottoms, sheltered from the current, as they crawl around. Their diet consists of feeding on fallen leaves from streamside trees and other aquatic vegetation. Some stoneflies are predatory feeding on caddis, midges, and mayflies.
A Stonefly emerger is unlike the other insect we talked about earlier. The difference is, instead of rising to the surface to hatch out into the adult stage on the water, stonefly emergers crawl to dry land onto rocks or plants. Once out of the water, they hatch into adults.
An Adult stonefly after hatching flies to live in vegetation along the creek. An adult life span is short, living from a few days to a few weeks. Unlike the mayfly, stonefly adults can feed, although, most don’t. They feed on pollen, nectar and other vegetation. In order to attract a mate, they perch in the vegetation and make a “drumming” noise by bouncing up and down on their perch. Following mating in the vegetation, the female flies back to the water where the fertilized eggs are dropped as she skates across the surface.
Terrestrials
The fifth group of the 5 bugs of fly fishing entomology to know?
Terrestrials are all the things that live predominantly or entirely on land, as opposed to the above bugs, that live in the water. The thing about terrestrials, it is a huge group of insects and other things. Beetles, spiders, moths, grasshoppers, crickets, bees, the list is endless and includes your dog, cat, and you. In other words, everything living on land.
But for us, it’s anything living on land that can be eaten by a trout. Mainly, a critter that lives near the trout stream or above it. Typically the imitations used by fly fishermen resemble ants, spiders, beetles, and grasshopper to name a few.
What Do You Mean By
“Getting Your Bugs In Order”?
In describing the different insects and the varying stages of development we should be able to select flies that better match the occurrence of things happening in front of us on the stream. That’s the idea, anyway. There are many patterns for each phase and most are designed to resemble not exactly match the bugs perfectly.
I separate my flies into fly boxes for each group. For example nymphs, emergers and dry flies. I have an additional box for streamers (More about streamers) and one for terrestrials. In each of these boxes, I have a small assortment of standard patterns and patterns of my own I tie. Within each box are a couple of patterns for each family class we talked about.
Nymphs
For midges, I have a few nymphs in mainly a black or red color. A Zebra midge is a good example of a black pattern and it can also be used as an emerger pattern by fishing it closer to the water surface. For caddis and mayflies, most nymph patterns will cover both families. As an example, a Hair’s Ear, Prince nymph, or Pheasant tail are good choices to start out with usually ranging in sizes from #12 to #18. The Stonefly nymph pattern has a different appearance because of its wing case and legs. Having a small assortment of stonefly nymphs of black or yellow in a few sizes is really all you need.
Emerger
When it comes to emerges I keep things as simple as I can. I use a wet fly pattern and the variations are based on color and size. A wet fly by design is fished below the water’s surface. The soft hackle of a wet fly creates “action” or “movement” that seems to be more important than the actual matching of a specific insect. For caddis, drab brown-and-yellow and brown-and-green or just drab gray-brown in sizes 14, 16, and 18 will cover almost all hatches. Mayfly patterns in tan in sizes 12 and 14; cream or yellow in sizes 16, 18, and 20; or olive in sizes 16, 18, and 20.
Dry Flies
This may be one of the most difficult categories to cover because a typical hatch can center around a specific bug. When these times are happening, having even the “perfect match” doesn’t always prove to be successful. But there are several general patterns for dry fly fishing that are proven to be ones to carry and use.
Starting with midges, as I mentioned before, Griffith’s Gnat is a good choice because it mimics the clusters of mating midges. Most caddis hatches can be covered using an Elk-haired caddis with size and color the most important aspect. An Adams is also another popular and effective mayfly pattern widely used. Again size and color are the variables.
The Stimulator is considered a “searching” fly because it resembles a variety of things, yet doesn’t resemble anything in particular. In large sizes with a salmon-orange body, it can be used to resemble the large black stonefly or the giant salmon fly. In smaller sizes and colors, it suggests yellow stoneflies, small yellow sallies or little brown stoneflies.
Terrestrials
I will be honest to say I don’t fish terrestrials very often with three exceptions. When nymph fishing I use a San Juan worm and wouldn’t be without that pattern. I lump it into the terrestrial world simply because it mimics a worm. Another is a Green Weenie which is an inchworm pattern. I have several patterns of inchworm I use but for the most part, it is color shades, size, and thickness that vary. Last and certainly not least are a couple of ant patterns in black and ginger colors. I also carry and rarely use a beetle pattern and a grasshopper or two.
Because I personally don’t do a lot of terrestrial fishing I use these patterns as “something to try” once in a while. Especially when I’m on a several days fishing trip, a chance to “play with something different” is always fun. Although, one creek near me is noted for its inchworm hatch and having an inchworm pattern is a must during that time.
How to Choose Flies to Use on the Stream?
Many of the streams I fish here in Pennsylvania are a combination of stocked and natural producing streams. I fish until these streams become frozen over where I’m forced to do my fishing in my head, as I sit at a fly tying bench creating the next generation of fly box goodies.
I mention this to set a stage for you to understand my approach to a stream. Generally, I stay away from a stream’s edge and simply watch the water. I look for “stuff” coming off the water and to see if anything is rising. If nothing is rising and bug activity is minimal, I walk to a shallow section and turn a rock or two over to see what lurks. From there I choose a nymph or two from my fly box that looks close to what I found and rig up for nymph fishing.
If there is bug activity, that is bugs coming off the water, I try to decide what it may be, caddis maybe or mayfly or something else. I look in the Fly box for size and color match. Then rig for dry fly fishing.
The rest of the day, quite frankly, is constantly paying attention to the world around me and the fish I can see in front of me. I make whatever adjustments I need based on the changes in the stream’s conditions as I make my way up or down the creek.
Here is an Interesting Analogy
Fishing reminds me of a game of golf, (of which I rarely play, but do enjoy it when I do). Like golf, each section of stream that comes into view is like playing a hole in golf. You have to decide on how to play the shot and what club to use. Fly fishing is similar because you have to select your fly and position yourself for the first cast. Every riffle, every pool, needs to be examined and figured out as to the best approach. The “hole in one” in fly fishing is, sizing up the hole, taking your first cast, and presenting the perfect presentation to an unsuspecting trout and – fish on!
Conclusion
As one progresses as a fly fisherman, his knowledge will, in turn, progress along with him. Bugs will become more familiar as you spend time on the creek paying attention to the world around you. The 5 bugs of fly fishing entomology to know, – you’ll know, – and as soon as you see one you will easily recognize what family it belongs. Additionally, your skills will improve so that your delivery of each of these bugs to their intended destination will be accurate and subtle. You’ll gain a better understanding of when to fish the top, bottom, or middle and what fly goes where and when. But interestingly enough fly fishing has another element to it that humbles us all who participate. We are and will be, at the mercy of the trout who always makes the final decision on whether we picked the right fly.
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