The older I get the more I dislike the sound of anything “micro.” Midges and Tricos provide enough eye straining challenges, thank you, now micro-caddis? Unfortunately it is true. While it may require buying another – stronger – pair of glasses to tie those size 22’s and 24’s, there are times when smaller is better, even for big fish. When it comes to many insects, nature seems to take perverse pleasure in things small. Tiny species often out compete larger ones by overwhelming them in shear abundance. This prolific approach to survival can produce some great, albeit frustrating, fishing opportunities, and micro-caddis fall perfectly into this category.

Many small caddis get called "micro-caddis," but true micro-caddis all belong to the family Hydroptilidae. This family is quite diverse, though few anglers are familiar with them. In North America the family Hydroptilidae contains 16 genera and over 200 species. The genera of greatest abundance and importance to anglers include Agraylea, Hydroptila, Leucotrichia and Oxyethira.

Generally anglers don't need to concern themselves with identifying the different types (genera and species) of micro-caddis. Knowing how to recognize the family Hydroptilidae, where and when they are abundant, and with what and how to imitate them, will prepare you with enough information to fish effectively when micro-caddis are abundant.

Knowing one when you see one!

Recognizing micro-caddis is largely a function of size. The largest species reach a length of about 6mm, roughly a size 18 hook. Most species, however, run between 3 and 5mm, or hook sizes 24 to 20, though I've seen hatches that make even a size 24 imitation look like Shaquile O'Neal next to Spud Web.

Besides their small size hydroptilid larvae can be recognized by:

There are few significant features of hydroptilid pupae to aide in recognizing them. The most helpful feature is simply their small size. General characteristics include:

Several characteristics make it relatively easy to recognize hydroptilid adults.

You can run into micro-caddis almost anywhere you fish. The family is widely distributed across North America with some of the greatest populations occurring in the warmer streams of the South and Southwest. These may be marginal trout waters, but plenty of micro-caddis live in cool trout streams in the North as well. Depending on the species, larvae can be found living on large rocks in moderately fast currents to slow sections of streams or even lakes. Several studies have found that larvae avoid the front and top surfaces of midstream boulders. One genus, Leucotrichia, however, often completely cover the upper surfaces of rocks in riffles and runs with their small elliptical flattened silk cases that look more like egg capsules than a caddis case. Larvae also occur in abundance on the surface of aquatic plants and algae in slow areas of streams, or the still waters of lakes.

Here’s what Carl Richards and Bob Braendle say about micro-caddis in their book Caddis Supper Hatches: “Can be very important at times if not overshadowed by larger species. Can be just about any color. These tiny caddisflies often emerge in huge numbers and at times fish feed selectively on them. Good imitations of pupae, emergers and adults are necessary even though these caddisflies are very small.”

Adult emergence can begin as early as June for a number of species, but peak activity generally occurs in July and August with many species continuing hatch activity into September. Because of their small size emergence activity goes unnoticed by most anglers. The best place to spot adults is on shoreline vegetation or boulders, where they run and flit with a nervous energy. When adults are observed along the stream and fish seem to be rising to some mysterious, unseen surface food, start thinking micro-caddis patterns.

The time of day emergence and egg laying activity takes place is not well documented for most species. In general mid-afternoon to evening is the best time to look for them on the water and available to fish. I have found it difficult to tell if fish are taking pupae rising to the surface or adults returning to lay eggs. In such cases I first try a pupa pattern. If that doesn't work I then put on an adult pattern. The type of water one fishes for pupae or adults is the same; moderate riffles and runs or the slow gentle currents of weedy flats.

The behavior of micro-caddis provides opportunity for fish to feed on the larvae, pupae and adults. Because larvae spend most of their time as free-living caddis, not building a case until the final instar, they become small but easy morsels for fish. Even the cased larva of most species drift in large numbers allowing ample opportunity to be fed upon. Their small size, however, makes it quite difficult to know when the larvae are abundant and in the drift. The only reliable way I have found to determine the presence or absence of larvae is by taking some samples with a kick net. Even this can underestimate their numbers and importance, since many are small enough to slip through the mesh of most nets.

The presence of adults along the shore is my cue to pay attention for micro-caddis activity on the water. The pupae may drift for some time near the surface before adults emerge. The tiny adults look more like midges drifting on the surface than caddis and trout respond to them with as much relish. After mating on the banks females fly back to the water for egg laying, which occurs underwater. The females dive or crawl several inches to several feet below the surface and paste small clusters of eggs on bottom rocks or weeds. They then let go and drift back to the surface. This activity often produces more interest from fish than the rising pupae. The number of egg laying adults can be impressive, and places that trap them in the surface and concentrate their numbers are important places to fish. This may include small eddies behind boulders, outside bends of the stream where the current pulls food and debris, and lanes of current formed between beds of aquatic plants.

Imitating micro-caddis

Micro-caddis provide all the challenge and frustration common when trying to imitate any of the micro hatches. Careful observation is a must. I have personally not taken on the challenge of fishing micro-caddis larval imitations. Some suggest that a size 18-22 copper Brassie provides a good imitation. Larval patterns should be fished dead drift through areas where larval numbers are high, like moderately fast riffles dotted with boulders, or below weed beds in slow moving sections of streams. Larval patterns for micro-caddis may also closely resemble midge larvae, increasing the odds that fish will find them of interest.

Pupa patterns are most often fished near the surface. Tiny sparsely dressed soft hackles or LaFontaine's sparkle pupae have proven effective. It is important to closely match the size of the natural. The minute pupae swim, but not with the same dashing moves of larger caddis pupae. Therefore, a dead drift or a retrieve with slight, gentle twitches is most likely to pay off. Fish may prove surprisingly selective to these small flies, so try to collect some naturals to get the size and color matched.

Adults often prove the most effective stage to imitate. This owes largely to the female's behavior of crawling or swimming underwater to lay her eggs, then drifting back up to the surface. Try a LaFontaine's diving caddis in very small sizes (20-22) fished behind boulders or in eddies and current lanes where the adults become concentrated. Other small caddis adult patterns that float low in the water or just below the surface also work well. Since there is little to no life left in these drifting females, their patterns should be fished dead drift. A good source for a variety of small patterns is the book Micropatterns by Darrel Martin. This book offers some unique and innovative patterns for hatches like the micro-caddis, as well as information on techniques and equipment for fishing minute flies of all types.

The world of the micro-caddis, and all small flies for that matter, is a world hard to contemplate and easy to overlook. Does such small size make a breeze seem like a tornado? Or does smallness allow shelter to be had in the smallest crease of a rock and thus avoid both breeze and tornado? The eyes of trout seem particularly sensitive to small things. As waters become more heavily fished, I often find small things the answer to catching more fish!

Special Note: A whole new order of insect has been recently discovered. This is the first new order of insects found in 80 years. While not aquatic and of no direct value to anglers this is quite a unique discovery: if it where a mammal it would be the equivalent of discovering bats. Considered a long lost relative of stick insects, which they somewhat resemble, the new order has been named Mantophasmatodea. Besides discovering specimens long ago hidden away at the London’s Natural History Museum, living specimens have been collected from grassy mountain slopes in Namibia. Fossils 40 to 50 million years old have also been found in Baltic amber from Europe.