While mayflies get most of the attention from angling entomologists, year in and year out, I catch more fish on caddis dry flies than on mayfly imitations and it is not all that close. And honestly with our mayflies declining, the gap is getting wider all the time. Caddisflies common name is a little less clear that is the name for mayflies - Ephemeroptera - but their order name - Trichoptera - means "hair wing" for their bristly wings. Like mayflies (Order Ephemeroptera), caddis have a great diversity of immature morphologies. Caddis live in a wide range of aquatic habitats and are found in riffles, runs, and pools - depending upon how they feed.
Caddis have a complete metamorphosis (holometabolism) meaning that like moths and butterflies (Order Lepidoptera), which caddis are closely related to, they go through a larval, pupal, and adult stage. And like mayflies, each of these stages are important for the fly angler. The importance of larva, pupa, and adults vary by family and species. For the angler in the Driftless Area, Tom Rosenbauer is wrong (watch the short video above) in my experiences because caddis are of greater importance than are mayflies. Sure, their names - particularly the Latin versions - are much less known.
Outside the Driftless, caddis are probably just as important as they here. However people do not know and understand caddisfly hatches as well as they do mayfly hatches. Fly fishing sort of "grew up" around mayflies. I know when I have fished both East and West of Wisconsin, I am fishing caddis dry flies at least as often as I am fishing mayflies.
Previous Angling Entomology posts:
Part 2 - Life Cycles (A simplified guide to knowing the bugs)
Tying the Life Cycle - Mayflies
Tying the Life Cycle - Caddis (this post)
Tying the Life Cycle - Midges (upcoming)
Tying the Life Cycle - Stoneflies (upcoming)
Larva
Caddis diversity is most evident in their larval stage. What comes to mind for many are the caddis that build cases that are held together by silk (remember they are closely related to moths and butterflies...) however caddis are much more diverse than that. Not only do some species build cases out of all sorts of materials, there are also free-living species and other which catch their food in silk nets (net-spinning caddis).
Caddis produce silk which they use for a variety of tasks - to build their cases, to hold them to rocks, to produce a net to catch food, and to pupate into an adult. Silk is a highly versatile material and caddis make great use of it.
Cased-building Caddis
Of the three major categories of caddis larvae, the case-building caddis are probably caddis that most anglers are familiar. It is not that they are necessarily the most important of the larvae - though some great hatches are case builders - but cased caddis are so readily visible. Grab a rock from a riffle on pretty much any trout stream anywhere and you are likely to find cased caddis. Depending upon where that stream is, you may find that they make their cases from sand, pebbles, organic matter, or other materials. In fact, caddis are rather easily identified through their cases.
The Grannom hatch (Brachycentrus spp.), probably the single best, most consistent hatch across the state of Wisconsin and maybe the Eastern United States (yeah, it is that important), is an organic case builder. These cases are quite distinctive in shape - they are like a four-sided ice cream cone (link to image from Macroinvertebrates.org). For more on the Grannom hatch, watch Tom Lager's excellent presentation on Grannoms (above).
There are a number of other species that do not hatch in the numbers that the Grannoms do but often provide excellent evening (and sometimes morning) fishing from May through June. Again, grab a rock and you are likely to see a number of caddis cases made from small pebbles. And there are a number of "saddle case" makers including Glossosoma spp. which can be very good and dependable hatches.
I have always thought fishing cased caddis as a bit unlikely to be a great method to catch fish as their cases are generally "glued" quite well to the rocks in riffles. However, I know many anglers that I respect that have done great on cased caddis patterns. And a number of all-purpose nymphs seem to have a hot spot similar to those of cased caddis patterns - often referred to as "peeping caddis". There are tons and tons of options for cased caddis fly patterns - I share the one above because it uses fire which always makes tying more fun. Many patterns use glue or epoxy and native substrates like sand and pebbles to match the case.
Net-Spinning Caddis
If the previously mentioned Grannom hatch is a sprint; the Hydropsyche hatch is a marathon. Rarely are there adult Hydropsyches in great numbers but May, June, and some July mornings and evenings almost guarantee enough of these net-spinning caddis to make fishing interesting - and make it so you can avoid fishing the dark arts. Rarely do Hydropsyche caddis hatch or return to the stream in great numbers but slow and steady wins the race. They are very common in Driftless streams - as well as streams elsewhere. As larva, Hydropsyche caddis have three very distinctive thoracic segments which are often imitated in flies such as Czech nymphs which are designed to mimic these widespread and prolific caddisflies. Much of the time, I am sure that the CDC and Elk dry fly that I am fishing in a #14 to #18 (or #19 to #15 on the Tiemco 102Y hook, my favorite for this pattern) are taken as spotted sedges, the common name for this group.
While Hydropsyches are the most important of the net-spinning caddis, there are other species that are important for shorter periods of time. Chimarra caddis - the little black sedges that typically hatch in May and early June - fairly often litter streamside vegetation. Their larva are typically a bright yellow color with a bit darker head. Information about this group is lacking and contradictory. I have never seen them hatch in great numbers but I have done well on both a bright yellow larva as a dropper behind another nymph or dry fly and on small, black caddis dry flies.
Going to probably the best source of information about caddis for the fly angler - Gary LaFontaine's most excellent book, Caddisflies - he writes that Chimarra egg layers do everything that a great dry fly insect should do. As larva and pupa, they are less cooperative as they crawl to shore and emerge in shallow water, hence it is a hatch we rarely see occurring. However, as egg laying adults returning to the stream, they are quite prevalent and active and this is the stage most anglers are imitating.
Free-Living Caddis
Free-living caddis are ancestral to the cased and later free-living caddis, meaning that they represent the evolutionarily primitive caddis larva life style. The diversity of the free-living caddis is much lower but one important genus in Wisconsin and elsewhere is Rhyacophila, the green rock worm. Although they are free-living, they do use a silk line that tethers them to rocks and they can repel back to their rock if they are dislodged. Some anglers have reported that coloring the last 12 inches or so of your leader white can be an effective way to mimic tethered, free-living caddis. Can not say I have ever gone to this effort. Rhyacophila larva are best fished in fast water, bouncing them along the bottom of the stream.
Pupa
Probably the most vulnerable stage for caddis are when they transition from pupa to adults. Pupation in caddis occurs in a variety of ways. For some, pupation is a short transition whereas other take significantly longer to transform from larva to pupa and then to adults. Caddis use their silk to build a pupal case, much like a butterfly or moth - but much smaller. In this case, they metamorphose from larva to pupa. The next metamorphosis is from pupa to aerial adult. As fly anglers, we are imitating the pupa that is about to metamorphose into an adult as the transition from larva to pupa is done in a much safer place.
Most caddis move through the water column as a pupa and transition to adulthood either during this time or soon after they reach the surface of the water. There is a great debate about whether or not caddis pupa fill their pupal exoskeleton with air bubbles to rise from the bottom to the surface. I can say I have never seen anything in the literature outside of something Gary LaFointaine had written about but has, to the best of my knowledge, never been verified by others. We lack a physiological explanation for how caddis that have lived underwater for a year can create an air bubble. It seems more likely that they simply swim quickly and use water currents to push them to the surface. We do know that adult egg laying caddis can carry an air bubble from the atmosphere underwater.
Probably the best known fly patterns to represent pupating caddis are LaFontaine's Emergent and Deep Sparkle Pupa. These flies - wait for it - were designed to imitate that air bubble that caddis may - but probably do not - create between their pupal exoskeleton and their developing adult exoskeleton. I do not pretend to know it all but I do know that these 1980's "relict" flies still get tied and fished today - though you probably will not find many in fly shop bins as "sexier" pupa patterns are sure to sell better. LaFontaine's flies often look a little odd but they are all well researched and tied for specific purposes. Some authors go as far as saying these are the only two caddisfly imitations you need to carry. I will add a third pattern - Hans Weilenmann's CDC and Elk - and be pretty happy with those three flies.
There are generally two different ways to fish caddis pupa imitations - swinging and moving them to imitate those emerging from the bottom to the surface and drifted in or very near the surface film as they complete their metamorphosis to aerial adults. Pupa and wet flies - a number of winged wet flies and soft hackles quite effectively imitate ascending pupa. The typical method to fish these flies is downstream, using the current to help bring the imitation to the surface. These quick moving pupa catch the trouts' attention and the often emerge in great numbers. Some of these "get stuck" in their pupal shuck (exoskeleton), typically near the surface or in the surface film, making them particularly vulnerable to trout. A fly like an X-caddis - a personal favorite - is a great imitation for this as I assume that CDC and Elk dry fly I usually have tied on. For much more detail about fishing caddis, this is a good start.
Pupa patterns are typically "messy" with things like CDC, zelon, feathers, or wildly picked out dubbing to imitate the developing wings and the shuck they will emerge from to become an aerial adult caddis. LaFontaine's sparkle pupa accomplish this with a trilobal Antron sparkle yarn.
Adults
Most of the time when the angler is fishing the adult caddis as a dry fly, they are imitating egg laying females returning to the water but at times we are imitating the adults just after they transitioned from pupa to adulthood and are ready to enter their aerial adult stage. In my experiences, this is particularly true for the Grannom hatch because they hatch when the water and air are both cooler so the time to dry their wings takes a little longer. This is a big part of what makes this my favorite hatch in Wisconsin's Driftless Area. Caddis are "bouncy" little insects - they flutter about and are quite active both when they first leave the water's surface and when they return to lay eggs. Unlike mayflies which live for hours or at most days before returning to lay eggs, caddis may live a month as an aerial adult.
There is a great amount of variability in how caddis return and lay their eggs. Many return to the water in mating swarms and the females will deposit eggs either from above the water or by dipping their abdomens into the water. Some, like the Grannom, will ride the surface for some time and then die after laying eggs, making them a fairly easy target. I tie that CDC and Elk with a little bright green Glo Brite Floss or similar material to imitate the egg sack that female Grannom carry. Other species dive or crawl underwater to deposit their eggs and do this quite actively. Diving species may be better imitated with a wet fly than a dry fly.
Emerging or just emerged caddis are imitated by low floating flies like the X-Caddis, Iris Caddis, and Hans Weilenmann's CDC and Elk. Al Troth's venerable Elk Hair Caddis is a great imitation for the higher floating dancing adults. If you read the blog, you know that my favorite pattern is the CDC and Elk and I fish it for just about every caddis hatch - it has even worked for a few mayfly hatches because I could not get my mayfly dry flies to skitter like the naturals that the trout were actively chasing. As always, we all come up with our own favorites and learn how to fish them more effectively over time. In the text above and further below are quite a number of patterns that you may want to give a chance.