UNDERSTANDING THE CADDIS
To become a more efficient angler during the caddis hatches, one must understand the caddisfly and the different stages of its life cycle.
CADDISFLY
Order: Trichoptera
Trichoptera means "Hair Wing". More than 200 species of caddisflies have been found in Montana waters. The adults are often called "sedges" and sometimes "moths" by the unknowing. The adults fly in a rapid and erratic manner. The sizes can vary from 8‑24. The basic colors are olive, gray, tan, brown and blackish. The adults live on the average of four weeks and tend to be crepuscular or nocturnal in nature. There are three ways that the caddis will lay their eggs:
1. Adults hovering (fluttering) just over the surface of the water.
2. Adults lying spent or at rest on the surface of the water.
3. Adults diving down to the bottom of the stream.
The caddisfly spends the majority of its time as an aquatic insect. There are a few species that produce two generations per year. But for the most part, one generation per year is the rule. The caddis has a complete life cycle (metamorphosis), going through egg, larvae, pupae and adult stages.
Caddis eggs are of no importance to the angler. Caddis larvae are found in forms, which do interest both the trout and the angler, they are "cased" and "free living". The cased caddis larvae are one of the most abundant to the trout and also one of the most abundant forms found in the waters of this area. The cases are made from small pieces of debris composed of sand grains, gravel, leaves, grasses, bark or twigs, and will generally blend in very well with the surrounding habitat. The head and thorax are the only parts of the insect that peek out of the case. The thorax colors will most often be olives, tans or cream. The heads are most often blackish in color. The free living caddis larvae is generally not quite as abundant to the trout, but trout can and do feed upon them during certain time periods and under certain conditions.
The larvae appear to be grub-like organisms, which either move about in search of food or build nets in the rocks and niches to trap food. The sizes will run between 8 and 22 (Mustad 37160). The larvae appear to have short tails with a long, segmented abdomen, short thorax section, legs and rather darkish heads. The base abdomen colors can cover a rather large range: from olives, tan, cream, grays, browns and blackish to mottled variations.
The most important tool that the angler can employ is that of observation. Once the general hatching time frame is established, the angler must endeavor to gain a knowledge of how the pupae rises to the surface, how the adults lay the eggs and what time periods are best for cased or larvae imitations, besides learning when and how each imitation is properly used. Sounds confusing, huh!! Well, it's not. The best way is to spend a little time afield sampling the insect forms in the area where you wish to fish.
Check with fly shops, guides and other anglers on hatching dates and do a little reading. Understand how the fish feed on each stage of the caddis. The efforts will pay off with more trout and larger trout.
[Editor’s note: The rest of this article contains information about caddis fly hatches in the Greater Yellowstone Area]
CADDIS HATCHES AROUND THE AREA
YELLOWSTONE RIVER
(Gardiner to Big Timber)
The first major hatch of the year is from April 25 to May 15. Due to annual run‑off, generally the river will go out by May 10, therefore plan accordingly. Also note that the weather can, and will, affect the timing of the hatch. This is the first major hatch of the year and every fish in the river is up for it. The first time most anglers fish the hatch their comment is "I didn't know that there were that many trout in the Yellowstone."
During this first hatch, the caddis appear in sizes 14‑16 (generally). The best colors to use are brown, olive and tans (for dries).
The second major caddis-hatching period on this section of river starts around June 25 and then there are various caddis emergences taking place until around August 30. The sizes and colors of the adults vary from the large tan sedge, which comes out in late June and is a size 8 to the small black caddis, which hatch in late August. These are a size 20 (sometimes smaller) and the angler/tier will find the colors as varied as the sizes in the adults.
UPPER MADISON RIVER
(Quake Lake to Ennis Lake)
This section of the Madison is a hotbed of caddis action. The hatches will start around the 20th of June and run to the 20th of August. The sizes of the insect will vary from the large tan sedge in 8‑10 clear down to the dusky purple sedge, which is a size 20.
LOWER MADISON RIVER
(Below the Beartrap to Three Forks)
The most productive hatch for the angler is the so-called Mother's Day Caddis Hatch. This hatch runs from about May 1 to June 1. Depending on the year, the lower Madison may be fishable during June and, if so, there can be some excellent fishing throughout the month using caddis patterns. During the Mother's Day Hatch the best colors are tans and olives and the sizes are between 14‑18.
Note: The Madison in this section can be fishing very well with only a few inches of visibility, but as the temps warm in June, the river can become unfishable due to rising water temps.
MISSOURI RIVER
(Below Holter Dam)
There are two major hatch periods on this section of the Missouri. The first one occurs between June 10 to July 15 and the second runs from August 1 to September 10. Often when other rivers are out during the annual run‑off in June, the Missouri can provide some excellent action for the caddis angler. The sizes run between 12 to micro 22's. Major colors of adults are pale olive, medium brown, tan and olive.
BIG HOLE RIVER
The Big Hole River offers some excellent caddis angling. The hatch starts toward the tail end of the salmon fly hatch around June 20 and continues throughout July. The best fishing is from June till about July 20. Best sizes are 14 and 16 in tans and olives.
BEAVERHEAD RIVER
The Beaverhead offers the caddis angler some fine fishing throughout the summer months with progressive hatches that occur from June 10 till September 10. The sizes will vary from 10‑20. Best colors are tan, olive, gray and black.
HENRY'S FORK RIVER
This is truly one of the finest rivers in the area for those seeking action during caddis hatches. From April 1 clear to October, somewhere on the "Fork" there are caddis hatches going on. The sizes will range from 8 all the way down to micro 22, and the colors will be assorted as well.
BIG HORN RIVER
The caddis hatch on the Horn is truly remarkable. The hatch runs from about the 15th of August to around October 1. The two caddis of major importance will be the little dark green caddis, which has a dark olive/green body and dark wing and will be in sizes 16‑20, and the tan caddis which has a tannish body and light wing and is best in sizes 14‑16. The trout on the Horn readily work the caddis nymphs, emergers and adults and offer the angler some very exciting fishing.
AREA LAKES
There are many area ponds and lakes that have good caddis hatches throughout the season. Three that readily come to mind: Hebgen Lake, which has several hatches from July 1 till August 20, with sizes ranging from 10 to 18. Then there is Quake Lake, which has some excellent hatches from July 10 till September 1. The two areas of Quake that I have found to be most productive are the inlet and flooded timber areas.
The third and final lake that offers excellent caddis fishing is Trout Lake, located in the northeast corner of Yellowstone National Park. The hatch times run from July 15 to August 30. Sometime around the second week of August one can run into a hatch of large green bodied caddis on Trout Lake. These flies are a size 8. The emergers come to the surface and hatch out and then the adults race toward the shore to dry their wings. This skittering, running caddis produces a feeding frenzy unlike anything you have ever seen.
Many other area lakes have fine caddis hatches besides the ones we listed.
YELLOWSTONE NATIONAL PARK
Firehole River
The caddis hatches on the Firehole will generally start right around opening day, which is the Saturday of the Memorial Day weekend and will run on into August. However, the best time for the angler to be fishing is between June 1 and June 20, before the water temps warm up. Once again in the fall, from mid-September until the Park closes, the fly fisher can encounter good hatches of small dark caddis from size 18 to 22. This is my favorite time to fish the Firehole!
Madison River
The Madison River also offers the angler some excellent caddis hatches. These hatches begin around the 5th of June and run till August. I have found the best time to fish these hatches is from June 5 to July 1.
Upper Yellowstone River
The river is also a hotbed of caddis action. For the angler the hatches will begin July 15 and continue till early September. The best colors are olive and tan in sizes 14‑18.
Slough Creek
From around July 5 till August 15, Slough Creek offers some excellent and challenging fishing for the caddis angler. Often the caddis hatches are occurring during or just before other major hatches and the angler misses them. Many times when anglers report slow fishing during one of the major hatch periods, it's because the wrong patterns were being used. Often the trout are ignoring the more visible Pale Morning Dun or Gray Drakes and feeding on the caddis emergers.
Lamar River
During July and August the Lamar River has a number of caddis hatches and will produce some very good action for the caddis angler. Many times a caddis nymph or larva pattern is an excellent choice for use as a searching pattern.
Yellowstone River
(Central Section from the Falls to Park Boundary)
From June 15 till September 5, somewhere in this section of river there are caddis hatches taking place. One of my favorite sections of river is from the Park boundary upstream to Knowles Falls. In this area the angler can find browns, rainbows and cutthroats along with several dependable caddis hatches. Generally, this section of river is not fishable till early July.
These are just the highlights. There are many other lakes, ponds, streams and rivers that offer excellent fishing for the caddis angler. Please note that the weather conditions may affect the hatching dates. For those who wish to fish caddis hatches, somewhere in the area from April 1st to October 1st, one can chase the caddis across the region.