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Seasons of the Metolius,
Chapter IV
Caddis in March and April
Caddis Behavior
Spring comes slowly to the Metolius. In March and April a rim of green starts to form along the river, but the uplands remain fairly brown and barren. Though it can be warm and pleasant at times there are still plenty of days when it’s dark and cold. We can get snow clear into early May.
These late storms are seldom big ones, just an overnight dusting, a “grass-greener” that brings cool moisture to the budding plants along the river. By noon the snow has melted from the valley floor and there is only a white crown, high on the ridge, to serve as a subtle reminder that winter is not quite ready to relinquish its hold.
The fishing seems to reflect this mood. Despite a succession of caddis hatches and rapidly increasing numbers of insects, there is not much consistent feeding activity yet. You have to search a bit for the opportunity to catch fish. This search is compounded by the fact that caddis hatches can be very difficult to interpret. Mayflies are fairly easy to detect. The insects rest on the water strengthening their wings before they fly. They’ll often drift long distances, inviting the fish to make a rise. This means that cause and effect are visible to the angler. You see the bugs and you see them being taken by the fish.
Caddis activity is different. Caddis are of the order Trichoptera or hair-winged insects. Under microscopic examination their wings are covered with little hair-like structures called setae. The setae allow the insect to trap gasses along the wing thus, at the moment the insect bursts through the river’s surface, the wings are dry and ready for flight. The caddis waste no time; you will rarely see them drifting helplessly on the current like mayflies. Once in the air they are very quick and agile fliers that usually leave the river almost immediately. As a result it’s possible to have a very good hatch going on with very few bugs visible over the water.
Conversely there are times when there will be hundreds of caddis moving up-river in migratory flights without causing any reaction from the fish what-so-ever. During their life as a larva the caddis often drift downstream. When they emerge as winged adults they have an instinct, built in, to compensate. They fly up river right along the banks retracing their steps. This insures the entire stream will be populated with insects rather than having them all wind up down at the mouth of the river.
When they are engaged in these upstream flights the caddis don’t get on the water at all, they’re simply not available to the fish. This makes everything very confusing, it’s hard to figure out which bugs are hatching and which bugs are flying. There’s no correlation between the number of insects you see in the air and the actual hatch activity. This is further compounded by the fact that caddis have a swimming nymph form called a pupa.
Caddis Pupa
The caddis pupa is an elusive little piece of river life. It is an interim form of development that allows these insects to swim from the bottom of the river to the top. Caddis are what they call a three-stage insect. They appear first as a larva, then as a pupa and finally as a winged adult.
Most of the insect's life, a year or more, is spent as a larva. These worm or grub-like creatures crawl over the river bottom in search of a wide variety of foods. They are generally well protected from the trout because they make a portable shelter out of sand, gravel or woody material like pine needles and bark chips.
When the larva is mature it seals its case and, much like a caterpillar turning into a butterfly, it transforms into a caddis pupa. Once developed, the pupa will chew out of its case and swim toward the surface. This swimming pupa stage may last only a few minutes before the insect transforms into a winged adult. It is at this point, however, that the insect is the most vulnerable to marauding trout. Unlike the cased larva or the high flying adult, the pupa’s only defense is its ability to swim. When it lets go of the bottom and swims upward it is in the open and clearly visible to the trout
Unfortunately, these pupae are hidden from us. The life form is so transitory we almost never see it. In a lifetime of fishing I don’t think I have seen an actual pupa swimming in the water more than once or twice. There are really only two ways you’re likely to obtain a sample. One is from the stomach of a fish (use a sampler rather than killing the fish, please). The other is by opening up a caddis case just before the pupa is ready to hatch. Neither of these sample forms is a living, swimming, kicking, breathing caddis pupa so while they give a model for the general appearance of the pupa, they don’t really allow a full appreciation of the living insect and it’s behavior.
Distinguishing the Hatch
When I am trying to detect a caddis hatch I’m forced to watch for clues, I have to use my imagination to visualize the pupa releasing from there cases and they swimming swiftly upward. At the same time I think about how the trout react by chasing after them. With these thoughts in mind the first indicator of a hatch is flashes under water. When the trout are chasing pupa they dart and move quite quickly. Sometimes you’ll see the flashes of their bodies as they turn. When I see this behavior it’s an indicator there is something that the fish are chasing deep under water. If there are caddis around it’s a good bet that’s what the food item is.
A second indicator is an occasional sharp, splashy rise at the surface. The pupa are coming up fast and the fish are chasing them; occasional the fish will follow all the way to the top. This will result in fairly showy surface rise but because so much of the activity is still going on underwater these rises are not consistent like during a mayfly hatch. You’ll hear a splash and then wait several minutes before you hear or see another one. Even though that may not seem like much surface activity it does indicate a time when fish are likely to be keyed on caddis.
I get my third indicator of a hatch by watching the adult caddis very closely as they dart right over the river’s surface. Sometimes you’ll see them tumbling on the water for a split second just before they flying away. This odd behavior actually occurs when the insects emerge. Though caddis leave the water quickly, they don’t fly instantly, there’s usual a momentary pause right at the surface. During this time caddis often make a couple of flaps of their wings before they get airborne, it gives them an appearance of tumbling. When you see the behavior you can guess there is a hatch going on.
The insects
The first to arrival, in an on going series of spring hatches, is the Striped Winged caddis or Snow Sedge. These straw-colored insects are fairly large and easily identified by the distinct horizontal stripe along their wing, clearly visible when they are at rest. The larvae can be seen in shallow backwaters along the edge of the river, they are sometimes scattered over the sand by the hundreds. They build a tube-type case out of sand and gravel and often attach pine needles on the side for balance and concealment.
This insect species doesn't seem to have a very good internal clock, their hatches are more temperature-dependent rather than based on a specific time of year. Any time there is a series of warm days there will be a bit of emerging. The cycle is spread over a long period of time with the earliest arrivals being seen running along the snow banks in mid-winter while the later arrivals hatch in March or even early April.
Following the Stripe Wing comes the spring October Caddis. That's right – October Caddis in March and April. These big orange insects appear on the Metolius both at the beginning and the end of the season. While entomologists tell me this double hatching is not entirely unheard of, it is rather unusual, just another of the many mysteries of the Metolius. While the fall hatch is larger and more consistent, the April Octobers still bring some pretty good nymph fishing. Large orange caddis pupa imitations, often called carrot nymphs, can be productive. (There are some Bull Trout fisherman who think this is one of the hottest nymphing periods all season.)
A little later the smaller caddis begin to appear. The first of two major species you are likely to encounter is what I call the Speckled Wing caddis or Gammon. These insects have a light, mottled brownish-gray wing and a body that is light brown or brownish-olive. On occasion, freshly hatched specimens will show a distinctly light colored side stripe on the body underneath the wing.
The larva of the Speckled Wing builds a square, paper tube case. Sometimes the rocks in the riffles are covered with rows of these shelters. They’re all lined up right at the crest of the rock so that the larvae can reach up with their little claw-like front legs and gather whatever food and algae is drifting in the current.
Following a few weeks behind the Speckled Wing caddis is a slightly larger light orange or brownish-orange caddis I call the Spring Sedge. This is a very prolific hatch and these insects engage in some of the most spectacular upstream flights of any of the caddis. Hundreds of insects will be seen cruising right along the stream banks, just a few feet off the water, moving upstream like salmon returning from the sea.
This insect is probably a net-spinning caddis of some sort. The large, bright green larvae build a complex spider web like shelter. Little bits of gravel are incorporated in the web for concealment. For a long time I didn’t appreciate how delicate and beautiful these nets really were. I would find them by picking a rock out of the river but as soon the sample was out of the water the net would collapse. I though these shelters were nothing more than a mass of goop on the rock with a little green worm on the inside. One day I happened to examine a shelter under water. When it’s submerged and placed in a current, the net floats out and expands. It makes a tube-shaped funnel out of a delicate webbing much like a spider web. The larva has a little hotel at the back, a kind of antechamber where he hides in waiting. When food is caught in the web he comes out to gets it. Pretty sophisticated development for nothing more than a little green rock-worm.
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