Glossosoma Caddis - Saddle Case Maker Caddis

On the Lower Yuba River in years when we have drought conditions, as we have had late this spring and early summer, there is a hatch of bugs that often has us asking ourselves. "What the heck are the trout eating?" The rise forms are subsurface, sometimes a fish will rocket out of the water like a missile. Is it an early season caddis? In most years the late spring and early summer typically have high flows due to seasonal storms and then water being shipped for rice or for other obligations. The river runs too high to even notice what bugs are around. Some years you'd never even know that the March Browns are happening. This is also the case with early season caddis, most years you'd never even know they are there!

This year is different, there have been drought condition flows all this late spring. The early caddis have become players once again. It was time to go back to "Bug Detecting". I got out my bug screen out last week and found lots of caddis larva, cream and tan.  I also screened cases from hatched bugs in the flow that were amber colored. There are lots of domed shaped cased stuck to the rocks in the Lower River. I've turned rocks and screened bugs and picked the domed shaped cases apart that are glued to the rocks. These tan/amber colored larva are Glossosoma Caddis. Their common name is Saddle Case Maker Caddis.

Here's information that I have dug up.

"In almost every tumbling coldwater stream in California lives an insect that is very important to trout  throughout the late spring and summer. When you've been turning over rocks you've probably noticed all those little gobs of pebbles glued to in-stream boulders. They look sort of like barnacles. These scabs of pebbles also give a reference to high water levels. All of these clusters of pebbles are used to house an immature Glossosoma caddis".

"The Glossosoma are a member of the Family Glossosomatidae, the most primitive of all the case making caddis. These caddis have  a unique technique of building a home. Most caddis larvae make tubular homes that they simply extend as they grow. The Glossosoma builds a pebble covered dome that must be discarded and replaced as they mature. Sort of like a kid outgrowing his pants".  This fact is what leads them to be important to the fish and the angler.

Glossosoma Larva

"At dusk or dawn, large and in some stream huge numbers of Glossosoma larvae crawl out of their shelters and release themselves to the current. The numbers can be staggering. In one survey done by the late, great Gary LaFontaine, Glossosoma larvae attained drift rates of 350 insects per hour through a one square foot portion of river. Gary calculated that a trout with a three foot feeding area was seeing up 1,600 drifting larvae in one hour. LaFontaine concluded that during certain times of the year, Glossosoma create very selective feeding of the trout". They lock in to the Glossosoma caddis.

"When it is time for the larva to build a new home they crawl out of their too small abode and release themselves into the drift. The larvae might drift for a few feet or a few hundred yards before it lands on the streambed. It quickly begins gathering gravel and within a few  hours has built a new home. This home is dome shaped with a hole on the bottom at each end of the dome. Across the bottom of the dome is a belly band woven from silk".

"The larvae crawls and grazes on a rock while carrying the domed house along with it, searching for algae and plankton upon which to feed. The larvae might travel one direction for awhile then turn around inside its case, stick its head out the opposite hole and continue on in another direction. After a week or so, the case once again becomes uncomfortably snug and the larvae once more vacates its home and casts its destiny to the current". Once again making themselves available for the awaiting trout.

"Some segment of the Glossosoma population is doing this every dawn and dusk throughout the late spring and early California summer. The heaviest drifts are said to occur about an hour after sunset".

Glossosoma Pupae

"At some point the larvae decide it’s time to pupate. They aim the holes of their home so the current percolates through, providing a fresh flow of oxygen. Then, for the final time, they glue their case to the rock upon which it sits. This affixing of the case to the cobbles and boulders of the streambed is excellent insurance against getting inadvertently swept into the drift. It also spells certain death on our Lower Yuba should the powers that be who regulate the releases at the Englebright dam decide to abruptly drop the water level exposing the pupa glued to the rocks. This could be the case this year due to river fluctuations".

"After several weeks of pupation, the pupa chews itself free and emerges from the pebbled dome, sometimes in the morning but more commonly about an hour after sunset. These size 16, sort of burnt orange colored pupae are very active swimmers. They often congregate in the soft water immediately downstream of riffle areas. The pupae hide among the cobbles during the day, but at dusk they emerge to swim about in an erratic jinking movement".

"One or two evenings after emerging from their rocky homes, a pair of sparkling bubbles develop just under the pupal skin at the shoulders. Possibly aided by the buoyancy of these bubbles, the pupae swim to the surface, drift a short distance (about one minute) then the adult pops out and immediately flies upstream".

"About an hour after sunset, adult Glossosoma caddis return to the river to lay their eggs. Glossosoma are one of the many caddis species which crawl and swim underwater to lay their eggs on the streambed. Having lost their gills, the adults are obligatory free air breathers and must carry their oxygen supply with them. This they do by cloaking their entire bodies in a bubble of air".

"The bubble feeds oxygen to the caddis as it swims and crawls about the streambed. As the oxygen is consumed, the pressure differential shifts and oxygen from the water is drawn into the bubble thus replenishing the caddis’ supply. The bubble encrusted caddisflies look nothing less spectacular than sparkling, animated diamonds. In the relative dark of the evening stream bottom, the bubbles reflect any available light and seem to glow from within. To say these guys are highly visible is a gross understatement".

Information derived from Ralph Cutter's www.flyline.com and "Caddisflies" by Gary Lafontaine

Tactics for the Glossosoma Caddis

In many Sierra streams, just about every evening of early summer starting about an hour after sunset, #16 pale colored larvae free themselves from their homes and drift, en masse downstream. On the Lower Yuba these larvae are cream or light brown in color. Shortly thereafter, #16 burnt orange or purpilish colored pupae emerge from hiding and start swimming about. Many of these sport sparkling bubbles of air and ascend to the surface and emerge. Only a short time after that, #16 brown adult caddis from an earlier night’s hatch return to the river and travel about the stream bed to lay their eggs.

The typical fisherman experiences this sequence initially by seeing a sudden burst of caddis adults winging their way upstream. There might be thousands of bugs. At the same time, trout are rising, slashing and flashing about at or just below the surface. Many excited anglers tie on a #16 elk hair caddis and presents them on the top of the water for about twenty minutes until the rises stop and the caddis disappear. Rarely do they catch a fish. This is a common result for many anglers fishing the evening caddis hatch.

Birds Nest

First Phase of the Hatch

To be successful stay out late and fish until about an hour after sunset. Start by tying on a #16 orange, pink or cream colored larva imitation. Ralph Cutter recommends to use a Bird’s Nest as most people carry the pattern and they work pretty well. Add some split shot and high stick the imitation downstream in a drag free drift right along the river bed. You are imitating the helplessly drifting larvae. Trout will be looking for the larva in the drift along the bottom.

Glossosoma Larva

Second Phase of the Hatch

When the first trout rises and you see dorsal / tail rises, or you start to experience a burst of caddis activity, you will want to try a different tactic. Tie on a #16 Birds Nest or caddis pupa pattern and a small split shot. Rub the fly in powdered floatant and lob it out and across the stream. The nymph will be buoyant from the floatant but the shot will help it break the surface. Actively retrieve the fly with a twitchy and erratic strip. You are imitating the actively swimming pupae. The fish focus and concentrate on the emerging pupa. They rarely if ever take a dry imitation on the surface. All those rising, slashing fish you’re seeing are NOT taking adults, they are feeding on the pupa just under the surface. They will ignore a caddis dry floating on top of the film.

Deep Sparkle Pupa

Third Phase of the Hatch

As soon as the fish stop rising, use this as the key to switch tactics again. There may be lots of caddis in the air but once the fish move down in the water column you must present your flies back on the bottom. Take another Bird’s Nest or other diving caddis pattern, make sure it is bone dry, and treat it with powdered floatant. Fish the flies along the bottom of the riverbed with little or no drag. The rises stopped because the trout settled back down to the streambed to graze on the highly visible and vulnerable caddis adults egg layers.

Another Option - Fish a Caddis Cripple

If you’re in the mood for some dry fly action try using a Caddis Cripple pattern in a size #16. One great pattern for this is Cutter's E/C Caddis.  Its shuck-trailing, bicolor body supported by the flared wing and parachute hackle makes the E/C caddis (Emergent Crippled caddis) a great match for the crippled Glossosoma. Another great pattern is Craig Mathews' X-Caddis. The Glossosoma caddis do a very efficient job of emerging, but enough don’t survive the transition and a percentage of the adults gets trapped in the pupal shuck. This presents an opportunity for fishing a cripple pattern.

E/C Caddis

You can also fish a Caddis emerger immediately following the caddis hatch. It is also a good choice to use it as a searching pattern earlier in the late afternoon and evening prior to the fish rising. Fish seem to be attracted to a dead drifted cripple and will often suck them in even while other types of insects are in the drift. When you see caddis in the bushes in the early summer a Caddis Cripple is a great searching pattern prior to the hatch.